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HomeMy WebLinkAbout05182004 BSC Agenda Item 1 Rev. 6-2-04 Standard Codes Schedule Adoption. Subject to the amendments and deletions indicated beneath each code,each of the following codes, including all of its published appendices and attachments,is adopted, ordained and made a part of the Code of Ordinances of the City and of each chapter where it is referenced, except as otherwise expressly provided. Procedure for amendments,etc. The procedure for adopting new codes, updated codes,local amendments and provisions for administration and enforcement of these codes is as follows: (1)proposal by the building official or other appropriate City official, (2)referral to the Building&Standards Commission, (3)consideration by the City Council,after giving required meeting notices,and(4)adoption and publication,as required by Article II of the City Charter. International Building Code,2000 Ed.,International Code Council,Inc.. 1. The administrative officer is the building official. All hearings,variances etc. are handled by the BSC. 2. All roofs must have Class C or better fire resistance,as determined under Sec. 1505.1. 3. :: - - .. •■• :' :■ : : ■ :: .1 - •;• - - • .- : _ • • • GG■ ■ 7, • lr based on a soils report from a recognized and reputable firm or agency(Exception: no - gross floor area); and inspected by an RPE who certifies proper construction,before work proceeds further. All foundations and structural framing for new buildings with a gross floor area 485 square feet or more must meet the following criteria,as applicable. a. Engineering. Foundations and structural framing must be constructed in accordance with complete plans and specifications prepared, signed and sealed by a licensed or registered professional engineer who is: (1) employed by a registered engineering firm; and (2) covered by professional errors and omissions insurance with limits of at least $500,000 per year, aggregate, ("RLPE"). The plans and specifications must be prepared specifically for the site of the work, and they must meet criteria as to scope, content and form specified by the building official. b. Geotechnical Report. The plans and specifications for each foundation must be based on a written geotechnical report prepared, signed and sealed by a licensed or registered geotechnical engineer who is: (1) employed by a registered engineering firm; and (2) covered by professional errors and omissions insurance with limits of at least $500,000 per year, aggregate. The report must meet all applicable criteria in"Recommended Practice for Geotechnical Explorations and Re.orts" published b the Structural Committee of the Foundation Performance Association,Houston,Texas(Document#FPA-SC-04-0, Rev#0, 11 April 2001, issued for website publishing), a copy of which is on file in the City Secretary's office. However,the minimum depth of borings is 20 feet in all cases. c. Foundation Performance Standard. Each foundation must be designed, installed and constructed to achieve a soil movement potential of one inch or less, determined by the estimated depth of the active zone in combination with at least two of the following methods: (1) Potential vertical rise(PVR)determined in accordance with Texas Department of Transportation Method 124-E,dry conditions, as publishing in and dated (2) Swell tests performed in accordance with[ASTM Standard/datel. (3) Suction and hydrometer swell tests performed in accordance with [ASTM Standard/date]. (4) linear shrinkage tests performed in accordance with [ASTM Standard/date]. d. Foundations. Basic T se. Each foundation must be of an approved basic i.e. Approved basic types are listed below. In this list, types of foundations are defined and described in"Foundation Design Options For Residential and Other Low-Rise Buildings on Expansive Soils"published by the Structural Committee of the Foundation Performance Association, Houston,Texas (Document#FPA-SC-01-X, Rev#X, 1 April 2004, issued for FPA peer review), a copy of which is on file in the City Secretary's office. (1) Structural slab with void space and deep foundations. (2) Structural floor with crawl space and deep foundations. (3) Stiffened structural slab with deep foundations. (4) Stiffened non-structural slab with deep foundations. (5) Grade-supported stiffened structural slab. (6) Grade-supported stiffened non-structural slab. (7) Grade-supported non-stiffened slab of uniform thickness(approved for one- story accessory buildings containing only garage or storage space). (8) Mixed-depth system for all new building construction. (9) Mixed-depth system for building additions with deep foundations. (10) Mixed-depth system for building addition with shallow foundations. (11) Another type approved by special exception issued by the BSC (see below). e. Foundations. Deep Support Components. Deep support components must be of an approved type. Approved types are listed below. In this list,types of deep support components are defined and described in"Foundation Design Options For Residential and Other Low-Rise Buildings on Expansive Soils"published by the Structural Committee of the Foundation Performance Association, Houston, Texas(Document# FPA-SC-01-X,Rev#X, 1 April 2004, issued for FPA peer review), a copy of which is on file in the City Secretary's office. (1) Drilled and underreamed concrete piers. (2) Drilled straight-shaft concrete piers. (3) Auger-cast concrete piles. (4) Another type approved by special exception issued by the BSC (see below). f. Foundations, reinforcement. Reinforcement for each foundation must be of an approved type. Approved types are listed below. In this list, types of reinforcement are defined and described in"Foundation Design Options For Residential and Other Low-Rise Buildings on Expansive Soils"published by the Structural Committee of the Foundation Performance Association,Houston, Texas(Document# FPA-SC-01-X, Rev#X, 1 April 2004, issued for FPA peer review), a copy of which is on file in the City Secretary's office. (1) Deformed bar reinforcing. (2) Welded wire fabric reinforcing(approved for one-story accessory buildings containing only garage or storage space). (3) Another type approved by special exception issued by the BSC (see below). g. Foundations. Observation & Certification. Each foundation must be professionally observed and must be certified by an RLPE,as more fully described below: (1) Observations must: (i) be performed either by the certifying RLPE or by a person under that RLPE's direct supervision and control whose professional qualifications are approved by the RLPE, (ii) include actual measurement of piers, fill, compaction,reinforcement, forms,materials,dimensions, structural elements, stressing,tendons, tensions,attachments, etc.before the work is covered or concrete is placed, (iii) be performed continuously during placement of concrete and any stressing or tensioning_operations, and (iv) be documented in a form and manner approved by the building official (which may include photographs). (2) Certifications must: (i) refer to and be based upon the professional observations required by this section, (ii) state that the work complies with the plans and specifications last approved by the building official (with any field changes that are ordered by the RLPE and reported to the building official and that comply with applicable regulations), (iii) state that the work complies with sound engineering practices, (iv) comply with criteria as to form and content as may be specified by the building official, (v) be signed and sealed by the certifying RLPE, and (vi) be filed with the Building Official before framing commences atop the foundation(and before the foundation is otherwise covered). h. The BSC may issue a special exception from any requirement in subsection"a" through"g,"above,but only upon a showing that: (1) the requirement will not affect life safety or the performance of a structure (for its estimated useful life): or (2) an alternate requirement to be imposed by the special exception will provide equal or better protection for life safety and long-term structural performance. In connection with any such special exception, the BSC may require that the applicant provide supporting engineering data and opinion, and the BSC may impose conditions to carry out the purpose and intent of applicable regulations. 4. All concrete piers, footings and foundations must be cured for at least 72 hours before any significant load is placed on them. 5. All walls and ceilings within a R-1,R-2, R-3 and R-4 type occupancy shall be sheathed with Type X gypsum board at least 5/8-inch(15.9 mm)thick. Exception: Where this code(IBC) requires otherwise for moisture protection. 6. Delete: Appendices A(Employee Qualifications),B (Board of Appeals) and D (Fire Districts). International Energy Conservation Code, as it existed on May 1,2001,International Code Council,Inc. 1. The administrative officer is the building official. All hearings,variances etc. are handled by the BSC. 2. In lieu of inspection by City employees,the building official may require a written certification that a building meets or exceeds minimum requirements,if the certification is: (i)signed by a code-certified inspector(as defined in Section 388.02,TEX. HEALTH& SAFETY CODE) not employed by the city, and(ii)accompanied by an approved inspection checklist,properly completed, signed and dated by the inspector. If the fees of the code-certified inspector are paid by the City, the amount shall be added to the building permit fees otherwise payable. With approval from the building official, a permittee may pay such fees directly to an independent inspection firm. Only code-certified inspectors may perform inspections and enforce this code in the City. International Fire Code,2000 Ed.,International Code Council,Inc. 1. The fire official shall be the fire chief or acting fire chief,who may detail other members of the fire department or the building inspection division to act as inspectors. Chapter 6 of this Code shall apply to enforcement and administration of the fire code in the same manner as it applies to the building code (except that the fire official shall have the powers and duties of the building official under such articles). 2. The BSC shall have the same jurisdiction and authority with respect to the fire code as it has with respect to the building code. 3. The limits of the fire district referred to in Section 902.1.1 are coextensive with the City limits. 4. Explosives and fireworks, as defined in Chapter 33,are prohibited within the City limits. 5. Notwithstanding Section 2206.7.6(relating to service stations),"latch-open"type devices are prohibited. 6. Section 603.8.4 (hours for burning)is amended to read in its entirety as follows: "An incinerator shall not be used or allowed to remain with any combustion inside it: (i)at any time from an hour preceding sunset on one day until sunrise the following day; or(ii)at any time when unattended." (7) Delete: Appendices FA(Board of Appeals),FE(Hazard Categories),FF(Hazard Ranking) and FG(Cryogenic Fluids -Weight and Volume Equivalents). International Fuel Gas Code,2000 Ed.,International Code Council,Inc. 1. The administrative officer is the building official. Chapter 6 of this Code shall apply to enforcement and administration of this code in the same manner as it applies to the building code. The BSC shall have the same jurisdiction and authority with respect to this code as it has with respect to the building code. 2. Delete Sections FG103,FG106 and FG10. 3. Even if permitted by this code, copper tubing shall not be used for the yard service line. 4. Amend Section 311.2 to read in its entirety as follows: "Low pressure (not to exceed 0.5 PSI) gas piping shall withstand a pressure of at least 10 inches of mercury for a period of time not less than 10 minutes without showing any drop in pressure,except that the following shall apply in the case of new construction: The newly-constructed system must withstand a pressure of at least 25 PSI for a period of not less than 10 minutes without showing any drop in pressure as an initial pressure test,and the system must also withstand a pressure as a final test. Higher pressure piping must withstand pressure of at least 10 PSI,but never less than twice the maximum pressure to which the piping will be subjected in operation, for a period of at least 10 minutes without showing a drop in pressure,but the higher pressures required for new construction,above, shall be used to test new construction in lieu of the 10-PSI level prescribed by this sentence." 5. There must be a permanently-installed stairway,either fixed or folding,to serve attic space where appliances or equipment are located. 6. Even if permitted by this code,undiluted liquefied petroleum gas, or"LPG", shall not be used at any fixed location in the City. Exception: This does not prohibit the use of such gas in quantities of 10 gallons or less. 7. Each new or replaced gas meter shall be located on the same building site that it serves. International Mechanical Code,2000 Ed.,International Code Council,Inc.. 1. The administrative officer is the building official. All hearings,variances etc. are handled by the BSC. 2. Add to Section M306.3: "There must be a permanently-installed stairway, either fixed or • folding,to serve attic space where appliances or equipment are located." 3. Add to Section M603: "All return air ducts must be installed within 10 inches of the finished floor in all new residential construction and wherever possible in existing buildings." 4. Delete: Appendix MB (Recommended Permit Fee Schedule). International Plumbing Code,2000 Ed., International Code Council,Inc. 1. The administrative officer is the building official. Chapter 6 of this Code shall apply to enforcement and administration of this code in the same manner as it applies to the building code. The BSC shall have the same jurisdiction and authority with respect to this code as it has with respect to the building code. 2. Delete: Sections P103,P106 and P109 and Appendices PA(Plumbing Permit Fee Schedule) and PG(Vacuum Drainage System). 3. Add at the beginning of Section 303.1: "Even if permitted by this code(IPC), ,none of the following is allowed for use in the City: Acrylonitrile-Butadiene-Styrene(ABS)pipe or fittings, polyethylene pipe or fittings, Type M copper, lead-based pipe, aluminum DWV pipe or components,or air admittance valves." 4. Even if permitted by this code(IPC),PVC and CPVC type water pipe and fittings are not allowed for use in the City. Exception: PVC water pipe may be used where permitted by this code(IPC),but only if: (i) it is installed underground and(ii) all joints are primed and glued as required by the manufacturer's recommendations(and the primer must be purple or another distinctive color, except on above-ground pool piping). 5. Even if permitted by this code(IPC),wet venting shall not be allowed except when authorized by the BSC, as a special exception for hardship and unusual cases. 6. Amend Section 1101.2 to read in its entirety as follows: "The provisions of this chapter are applicable to interior leaders,building storm drains,building storm sewers, exterior conductors, downspouts,roof gutters and other storm drainage fixtures and facilities." 7. Maximum water meter size,unless an RPE can clearly and convincingly demonstrate the need for a larger meter in a particular case, is: 3/4ths-inch for an irrigation system, or 1-inch for a single-family dwelling. International Residential Code, as it existed on May 1,2001,International Code Council, Inc.. 1. The administrative officer is the building official. All hearings,variances etc. are handled by the BSC. 2. This code, in lieu of the other"International Codes," applies to all residential structures in the City. "Residential"means having the character of a detached one-family or two-family dwelling that is not more than three stories high with separate means of egress, including the accessory structures of the dwelling. This code does not apply to: (i)any dwelling that has a common means of egress, such as a common hallway,or(ii) any dwelling or structure that has the character of a facility used for accommodation of transient guests or a structure in which medical,rehabilitative, or assisted living services are provided in connection with the occupancy of the structure. 3. All amendments and deletions to the other"International Codes"adopted by this Schedule are also carried forward and adopted as amendments and deletions from the International Residential Code. 4. Delete: Appendices RAF (Radon Control Methods),RAI(Private Sewage Disposal),and RAE(Manufactured Housing Used as Dwellings). 5. This code does not apply to installation and maintenance of electrical wiring and related components. See National Electrical Code,below. (BOCA)National Building Code, 1996 Ed.,Building Officials & Code Administrators International,Inc. Only Sections 3108 (Radio And Television Towers)and 3109 (Radio And Television Antennas),together with any necessary definitions or interpretative aids, are adopted. See Subchapter G of Chapter 6 of this Code. National Electrical Code, as it existed on May 1, 2001,National Fire Protection Association, ("NEC"). 1. The administrative officer is the building official. All hearings,variances etc. are handled by the BSC. 2. See Chapter 8 of this Code for various provisions which override or supplement the NEC. Standard Housing Code, 1997 Ed., Southern Building Code Congress International,Inc. 1. The administrative officer is the building official. All hearings,variances etc. are handled by the BSC. r . Rev. 6-2-04("clean') Standard Codes Schedule Adoption. Subject to the amendments and deletions indicated beneath each code, each of the following codes, including all of its published appendices and attachments, is adopted,ordained and made a part of the Code of Ordinances of the City and of each chapter where it is referenced, except as otherwise expressly provided. Procedure for amendments,etc. The procedure for adopting new codes, updated codes, local amendments and provisions for administration and enforcement of these codes is as follows: (1)proposal by the building official or other appropriate City official, (2)referral to the Building&Standards Commission, (3)consideration by the City Council, after giving required meeting notices, and(4)adoption and publication,as required by Article II of the City Charter. International Building Code,2000 Ed., International Code Council, Inc.. 1. The administrative officer is the building official. All hearings,variances etc. are handled by the BSC. 2. All roofs must have Class C or better fire resistance, as determined under Sec. 1505.1. 3. All foundations and structural framing for new buildings with a gross floor area 485 square feet or more must meet the following criteria,as applicable. a. Engineering. Foundations and structural framing must be constructed in accordance with complete plans and specifications prepared, signed and sealed by a licensed or registered professional engineer who is: (1) employed by a registered engineering firm; and (2) covered by professional errors and omissions insurance with limits of at least$500,000 per year, aggregate, ("RLPE"). The plans and specifications must be prepared specifically for the site of the work, and they must meet criteria as to scope,content and form specified by the building official. b. Geotechnical Report. The plans and specifications for each foundation must be based on a written geotechnical report prepared, signed and sealed by a licensed or registered geotechnical engineer who is: (1) employed by a registered engineering firm; and (2) covered by professional errors and omissions insurance with limits of at least$500,000 per year, aggregate. The report must meet all applicable criteria in"Recommended Practice for Geotechnical Explorations and Reports"published by the Structural Committee of the Foundation Performance Association, Houston, Texas(Document#FPA-SC- 04-0,Rev#0, 11 April 2001, issued for website publishing), a copy of which is on file in the City Secretary's office. However,the minimum depth of borings is 20 feet in all cases. c. Foundation Performance Standard. Each foundation must be designed, installed and constructed to achieve a soil movement potential of one inch or less, determined by the estimated depth of the active zone in combination with at least two of the following methods: (1) Potential vertical rise (PVR) determined in accordance with Texas Department of Transportation Method 124-E, dry conditions,as publishing in and dated (2) Swell tests performed in accordance with [ASTM Standard/date]. (3) Suction and hydrometer swell tests performed in accordance with [ASTM Standard/date]. (4) linear shrinkage tests performed in accordance with [ASTM Standard/date]. d. Foundations, Basic Type. Each foundation must be of an approved basic type. Approved basic types are listed below. In this list,types of foundations are defined and described in"Foundation Design Options For Residential and Other Low-Rise Buildings on Expansive Soils"published by the Structural Committee of the Foundation Performance Association,Houston,Texas(Document#FPA- SC-01-X, Rev#X, 1 April 2004,issued for FPA peer review), a copy of which is on file in the City Secretary's office. (1) Structural slab with void space and deep foundations. (2) Structural floor with crawl space and deep foundations. (3) Stiffened structural slab with deep foundations. (4) Stiffened non-structural slab with deep foundations. (5) Grade-supported stiffened structural slab. (6) Grade-supported stiffened non-structural slab. (7) Grade-supported non-stiffened slab of uniform thickness(approved for one-story accessory buildings containing only garage or storage space). (8) Mixed-depth system for all new building construction. (9) Mixed-depth system for building additions with deep foundations. (10) Mixed-depth system for building addition with shallow foundations. (11) Another type approved by special exception issued by the BSC (see below). e. Foundations, Deep Support Components. Deep support components must be of an approved type. Approved types are listed below. In this list,types of deep support components are defined and described in"Foundation Design Options For Residential and Other Low-Rise Buildings on Expansive Soils"published by the Structural Committee of the Foundation Performance Association,Houston, Texas (Document#FPA-SC-01-X, Rev#X, 1 April 2004, issued for FPA peer review),a copy of which is on file in the City Secretary's office. (1) Drilled and underreamed concrete piers. (2) Drilled straight-shaft concrete piers. (3) Auger-cast concrete piles. (4) Another type approved by special exception issued by the BSC (see below). f. Foundations, reinforcement. Reinforcement for each foundation must be of an approved type. Approved types are listed below. In this list,types of reinforcement are defined and described in"Foundation Design Options For Residential and Other Low-Rise Buildings on Expansive Soils"published by the Structural Committee of the Foundation Performance Association,Houston, Texas(Document#FPA-SC-01-X,Rev#X, 1 April 2004, issued for FPA peer review), a copy of which is on file in the City Secretary's office. (1) Deformed bar reinforcing. (2) Welded wire fabric reinforcing(approved for one-story accessory buildings containing only garage or storage space). (3) Another type approved by special exception issued by the BSC (see below). g. Foundations, Observation & Certification. Each foundation must be professionally observed and must be certified by an RLPE,as more fully described below: (1) Observations must: (i) be performed either by the certifying RLPE or by a person under that RLPE's direct supervision and control whose professional qualifications are approved by the RLPE, (ii) include actual measurement of piers, fill,compaction, reinforcement,forms,materials,dimensions, structural elements, stressing,tendons,tensions,attachments, etc.before the work is covered or concrete is placed, (iii) be performed continuously during placement of concrete and any stressing or tensioning operations, and (iv) be documented in a form and manner approved by the building official(which may include photographs). (2) Certifications must: (i) refer to and be based upon the professional observations required by this section, (ii) state that the work complies with the plans and specifications last approved by the building official (with any field changes that are ordered by the RLPE and reported to the building official and that comply with applicable regulations), (iii) state that the work complies with sound engineering practices, (iv) comply with criteria as to form and content as may be specified by the building official, (v) be signed and sealed by the certifying RLPE, and (vi) be filed with the Building Official before framing commences atop the foundation(and before the foundation is otherwise covered). h. The BSC may issue a special exception from any requirement in subsection"a"through"g,"above,but only upon a showing that: (1) the requirement will not affect life safety or the performance of a structure (for its estimated useful life); or (2) an alternate requirement to be imposed by the special exception will provide equal or better protection for life safety and long-term structural performance. In connection with any such special exception,the BSC may require that the applicant provide supporting engineering data and opinion, and the BSC may impose conditions to carry out the purpose and intent of applicable regulations. 4. All concrete piers, footings and foundations must be cured for at least 72 hours before any significant load is placed on them. 5. All walls and ceilings within a R-1,R-2,R-3 and R-4 type occupancy shall be sheathed with Type X gypsum board at least 5/8-inch(15.9 mm)thick. Exception: Where this code(IBC)requires otherwise for moisture protection. 6. Delete: Appendices A(Employee Qualifications),B (Board of Appeals)and D(Fire Districts). International Energy Conservation Code, as it existed on May 1,2001, International Code Council,Inc. 1. The administrative officer is the building official. All hearings,variances etc. are handled by the BSC. 2. In lieu of inspection by City employees,the building official may require a written certification that a building meets or exceeds minimum requirements,if the certification is: (i) signed by a code-certified inspector(as defined in Section 388.02,TEX. HEALTH & SAFETY CODE)not employed by the city, and(ii) accompanied by an approved inspection checklist,properly completed, signed and dated by the inspector. If the fees of the code-certified inspector are paid by the City,the amount shall be added to the building permit fees otherwise payable. With approval from the building official,a permittee may pay such fees directly to an independent inspection firm. Only code-certified inspectors may perform inspections and enforce this code in the City. International Fire Code,2000 Ed., International Code Council,Inc. 1. The fire official shall be the fire chief or acting fire chief,who may detail other members of the fire department or the building inspection division to act as inspectors. Chapter 6 of this Code shall apply to enforcement and administration of the fire code in the same manner as it applies to the building code (except that the fire official shall have the powers and duties of the building official under such articles). 2. The BSC shall have the same jurisdiction and authority with respect to the fire code as it has with respect to the building code. 3. The limits of the fire district referred to in Section 902.1.1 are coextensive with the City limits. 4. Explosives and fireworks,as defined in Chapter 33, are prohibited within the City limits. 5. Notwithstanding Section 2206.7.6 (relating to service stations), "latch-open"type devices are prohibited. 6. Section 603.8.4 (hours for burning)is amended to read in its entirety as follows: "An incinerator shall not be used or allowed to remain with any combustion inside it: (i)at any time from an hour preceding sunset on one day until sunrise the following day; or(ii)at any time when unattended." (7) Delete: Appendices FA(Board of Appeals),FE(Hazard Categories), FF (Hazard Ranking) and FG(Cryogenic Fluids-Weight and Volume Equivalents). International Fuel Gas Code, 2000 Ed.,International Code Council,Inc. 1. The administrative officer is the building official. Chapter 6 of this Code shall apply to enforcement and administration of this code in the same manner as it applies to the building code. The BSC shall have the same jurisdiction and authority with respect to this code as it has with respect to the building code. 2. Delete Sections FG103,FG106 and FG10. 3. Even if permitted by this code, copper tubing shall not be used for the yard service line. 4. Amend Section 311.2 to read in its entirety as follows: "Low pressure(not to exceed 0.5 PSI)gas piping shall withstand a pressure of at least 10 inches of mercury for a period of time not less than 10 minutes without showing any drop in pressure, except that the following shall apply in the case of new construction: The newly-constructed system must withstand a pressure of at least 25 PSI for a period of not less than 10 minutes without showing any drop in pressure as an initial pressure test, and the system must also withstand a pressure as a final test. Higher pressure piping must withstand pressure of at least 10 PSI,but never less than twice the maximum pressure to which the piping will be subjected in operation, for a period of at least 10 minutes without showing a drop in pressure, but the higher pressures required for new construction,above, shall be used to test new construction in lieu of the 10-PSI level prescribed by this sentence." 5. There must be a permanently-installed stairway, either fixed or folding,to serve attic space where appliances or equipment are located. 6. Even if permitted by this code,undiluted liquefied petroleum gas,or"LPG", shall not be used at any fixed location in the City. Exception: This does not prohibit the use of such gas in quantities of 10 gallons or less. 7. Each new or replaced gas meter shall be located on the same building site that it serves. International Mechanical Code,2000 Ed.,International Code Council,Inc.. 1. The administrative officer is the building official. All hearings,variances etc. are handled by the BSC. 2. Add to Section M306.3: "There must be a permanently-installed stairway, either fixed or folding,to serve attic space where appliances or equipment are located." 3. Add to Section M603: "All return air ducts must be installed within 10 inches of the finished floor in all new residential construction and wherever possible in existing buildings." 4. Delete: Appendix MB (Recommended Permit Fee Schedule). International Plumbing Code,2000 Ed., International Code Council,Inc. 1. The administrative officer is the building official. Chapter 6 of this Code shall apply to enforcement and administration of this code in the same manner as it applies to the building code. The BSC shall have the same jurisdiction and authority with respect to this code as it has with respect to the building code. 2. Delete: Sections P 103, P106 and P109 and Appendices PA(Plumbing Permit Fee Schedule)and PG(Vacuum Drainage System). 3. Add at the beginning of Section 303.1: "Even if permitted by this code(IPC), ,none of the following is allowed for use in the City: Acrylonitrile-Butadiene-Styrene(ABS)pipe or fittings,polyethylene pipe or fittings, Type M copper, lead-based pipe, aluminum DWV pipe or components, or air admittance valves." 4. Even if permitted by this code(IPC),PVC and CPVC type water pipe and fittings are not allowed for use in the City. Exception: PVC water pipe may be used where permitted by this code(IPC),but only if: (i) it is installed underground and(ii)all joints are primed and glued as required by the manufacturer's recommendations(and the primer must be purple or another distinctive color,except on above-ground pool piping). 5. Even if permitted by this code(IPC),wet venting shall not be allowed except when authorized by the BSC, as a special exception for hardship and unusual cases. 6. Amend Section 1101.2 to read in its entirety as follows: "The provisions of this chapter are applicable to interior leaders,building storm drains,building storm sewers, exterior conductors, downspouts,roof gutters and other storm drainage fixtures and facilities." 7. Maximum water meter size,unless an RPE can clearly and convincingly demonstrate the need for a larger meter in a particular case,is: 3/4ths-inch for an irrigation system, or f- inch for a single-family dwelling. International Residential Code, as it existed on May 1,2001,International Code Council, Inc.. 1. The administrative officer is the building official. All hearings, variances etc. are handled by the BSC. 2. This code, in lieu of the other"International Codes," applies to all residential structures in the City. "Residential"means having the character of a detached one-family or two- family dwelling that is not more than three stories high with separate means of egress, including the accessory structures of the dwelling. This code does not apply to: (i)any dwelling that has a common means of egress, such as a common hallway,or(ii)any dwelling or structure that has the character of a facility used for accommodation of transient guests or a structure in which medical,rehabilitative,or assisted living services are provided in connection with the occupancy of the structure. 3. All amendments and deletions to the other"International Codes"adopted by this Schedule are also carried forward and adopted as amendments and deletions from the International Residential Code. 4. Delete: Appendices RAF (Radon Control Methods),RAI(Private Sewage Disposal),and RAE(Manufactured Housing Used as Dwellings). 5. This code does not apply to installation and maintenance of electrical wiring and related components. See National Electrical Code,below. (BOCA)National Building Code, 1996 Ed.,Building Officials& Code Administrators International,Inc. Only Sections 3108 (Radio And Television Towers)and 3109 (Radio And Television Antennas),together with any necessary definitions or interpretative aids,are adopted. See Subchapter G of Chapter 6 of this Code. National Electrical Code, as it existed on May 1,2001,National Fire Protection Association, ("NEC"). 1. The administrative officer is the building official. All hearings,variances etc. are handled by the BSC. 2. See Chapter 8 of this Code for various provisions which override or supplement the NEC. Standard Housing Code, 1997 Ed., Southern Building Code Congress International,Inc. 1. The administrative officer is the building official. All hearings,variances etc. are handled by the BSC. RECOMMENDED SCOPE OF GEOTECHNICAL ENGINEERING SERVICES FOR THE x CITY OF WEST UNIVERSITY MAY 2004 By David Eastwood, P.E. Foundations Foundations for residences in the City of West University will consist of either a structural slab or slab- on-fill type foundation systems. The structural slab foundation system may consist of a pier and beam with a crawl space or slab with void underneath it and supported on piers. In all cases, piers will be used to support the superstructure. Geotechnical Exploration The geotechnical exploration for residences in West University should be conducted by an accredited geotechnical engineering firm. The firm should be accredited by American Association of Laboratory Accreditation (A2LA) in geotechnical engineering. The accreditation should be current. A copy of the accreditation in geotechnical engineering should be placed as an appendix of the report. The firm should have a minimum of$1,000,000 errors and omissions insurance (professional liability insurance). Geotechnical Borings There shall be a minimum of two borings required for houses with slabs of up to about 3,000 sq. ft. Additional borings should be conducted for any additional 1500 sq. ft. of the floor slab areas. This includes the garage area as well. All borings will be a minimum of 25-ft deep. However, 20-ft borings are allowed if a portable rig has to be used. Laboratory Testing The laboratory testing will be determined by the geotechnical engineer. Some of these tests may include Atterberg limits, unconfined compression, torvane, hand penetrometer, soil suction, grain size analyses, etc. Engineering Report A geotechnical engineering report should include recommendations on the recommended foundation types, specifically the above-mentioned foundations. In addition, the report should discuss various foundation risks. The recommended pier depths should be specifically spelled out. Furthermore, the recommended fill thickness should clearly be presented. In addition, on sites where trees are present, the effected tree removal and/or dying needs to be considered in the evaluation of the recommended foundation system and its components. Furthermore, a picture of the site should be presented in the geotechnical report. I Quality Control and Testing The quality control in testing for residences should be conducted by the same firm that conducted the initial geotechnical report. This work will include earthwork testing, drilled footing observations, and concrete testing. All fill soils placed underneath the floor slabs should consist of structural fill with liquid limit less than 40 and plasticity index between 12 and 20. These soils should be compacted to a minimum of 95% maximum dry density (ASTM D698). Moisture contents between optimum and +3%. All the fill soils should be tested, at a minimum of four locations within the floor slab areas at each eight-inch lifts. The subgrade soils should be proofrolled and tested for density at four locations prior to fill placement. The subgrade soils should have the same level of compaction as the fill soils. This information should be provided at the completion to the city building official as well as the structural engineer. The construction of all the piers should be observed by the geotechnical engineer of the record or the structural engineer of the record. The piers should be check for proper depth, soils stratum, proper soil strength, the correct bell size and steel placement. The concrete for the drilled footings slab should be tested in compression. A minimum of four concrete cylinders should be made for every 50 yards of pour or portions of. Two of the cylinders will be broken at 7 days and two at 28 days. Submittals A copy of the geotechnical report together with all field testing and observations should be sent to the structural engineer of the record, the client, as well as the building official. All failed tests should be retested until passing results are achieved. The tests should include the following: o Proofrolling observations report o Proctor test reports o Subgrade density report o Fill compaction reports o Drilled footing installation report o Concrete compression test reports for the drilled footing and the slab All reports should be signed and sealed by a licensed professional engineer in the State of Texas. Word\marketing\westun iversity %.114-4N-.t>.Xi:414Y..;14;44"14114:14.1, 40,444i 54401. • C.,Prroillon TX 7%0 . , 4 , ;i1vV*,:li' '4%7 • r t',7479'; 3C3Q • Fax: (972) 713-9171 'Ff,% t,:j',,; .,rlive—f..'4<ek goo rie,arir g.corn April 26, 2004 Mr. Joe Glass 9215 Hilldale Houston, TX 77055 Re: Ceotechnical/Geophysical Investigation Proposed Glass Residence 9221 Elizabeth Road Houston, Texas 77055 BC1 Report No. 04-089 Dear Mr. Glass: Attached is our geotechnical report for the above referenced project. This project was authorized by you and performed in general accordance with our oral discussions. It has been a pleasure to perform this work for you. If during the course of this project we can be of further assistance, please do not hesitate to call. Sincerely, BRYANT CONSULTANTS, INC. 01"‘ # • 41,1 lc Y . • joHN T. BRyANT ,31 ',pot oGy John T. Bryant, PhD, P.G., RE. I. .% goi63 , President °.(1 • 41,284,, "le.c., et4 ./` Michael ID, Gehrig, RE. Staff Engineer Cc Ron Kelm, Forensic Engineers. inc. GEOTECHNICAL/GEOPHYSICAL INVESTIGATION at PROPOSED GLASS RESIDENCE HOUSTON, TEXAS Prepared for Mr. Joe Glass 9215 Hil!dale Houston, TX by BRYANT CONSULTANTS, INC. GEOTECHNICAL AND FORENSIC ENGINEERING CONSULTANTS CARROLLTON, TX 75006 BC! Report No. 04-089 April 26, 2004 TABLE OF CONTENTS PROJECT INFORMATION 1 SCOPE OF INVESTIGATION 1 FIELD OPERATIONS 1 LABORATORY TESTING 2 EVALUATION OF SITE INFORMATION 3 SUBSURFACE CONDITIONS 5 ELECTRICAL RESISTIVETY PROFILES 9 ANALYSIS AND RECOMMENDATIONS 12 EARTHWORK GUIDELINES 22 LIMITATIONS AND REPRODUCTIONS 25 FIGURES GMMIR Profile and Boring Location Plan 1 Tree Survey 2 GIS Map of Site 3 Logs of Boring B-1 4 Logs of Boring B-2 5 Moisture Content Profile 6 Hand Penetrometer Profile 7 Total Soil Suction Profile 8 Liquidity Index Profile 9 Swell Test Results 10 GMMIR Profile R1 11 Photographic Survey of Site 12 Rainfall Data for Houston Hobby 13 E — Log P Curve 14 Boring Log Legend 15 APPENDIX 1 - GUIDELINES FOR THE PLACEMENT OF CONTROLLED EARTHWORK GEOTECHNICAL/GEOPHYSICAL INVESTIGATION for PROPOSED GLASS RESIDENCE HOUSTON, TEXAS A. PROJECT INFORMATION BCI understands the proposed residence will be located at 9221 Elizabeth Road in Houston, Texas. It is our understanding the proposed construction will consist of a multiple story, single family dwelling. Final grades for the proposed residence were unavailable for our review. However, for this report, we assume that the proposed pad will be constructed within 18 inches of the existing grades. If cuts and/or fills exceed this assumption, then BCI should be contacted in order to determine if the recommendations in this report are still valid. No specific warranty program or other standards, except acceptable industry standards, were followed in this investigation. B. SCOPE OF INVESTIGATION The purposes of the study are to: 1) explore the general subsurface conditions at the site, 2) evaluate the pertinent engineering properties of the subsurface materials, 3) perform one Geo-electrical Moisture Material Imaging and Resistivity (GMMIR) profile and two geotechnical borings at this site and 4) provide recommendations and design parameters concerning suitable types of foundation systems. C. FIELD OPERATIONS I. Geotechnical Exploration Two geotechnical borings were performed on March 17, 2004. The borings were drilled at the approximate locations shown on Figure 1 — GMMIR Profile and Boring Location Plan. A continuous flight auger drilling rig was used to advance the borings to a depth of 25 to 30 feet below grade. Undisturbed specimens of cohesive soils were obtained at intermittent intervals with nominal 3-inch diameter thin-walled, seamless tube samplers. Disturbed Proposed Glass Residence Page 2 samples were also retrieved using augering techniques. These specimens were extruded in the field, logged, sealed and packaged to help protect them from disturbance and to help maintain their in-situ moisture content during transportation to our laboratory. Figures 4 and 5 present descriptions of the soil properties and Figures 6 to 10 present a summary of the laboratory data. II. Geophysical Exploration In conjunction with the geotechnical borings, some additional information regarding the location of moisture and material differences around the perimeter of the structure was obtained using the geo-electrical moisture/material imaging method (GMMIR). Two geo-electrical (electrical resistivity) profiles were originally performed at the location of the proposed residence. However, equipment malfunction result in errant data from one of the profile and therefore will not be included in this report. Profile R1 was taken across the residential lot to characterize the conditions of the soils and the resistivity structure beneath the surface as presented on Figure 1. Measurements of the field resistivity were performed in general accordance with ASTM G-57 with modifications of the electrode configuration. Figure 11 provides a depth profile of GMMIR Profile R1 geo-electrical resistivity model. III. Benchmark Installation After drilling operations were complete in Boring B-1, BCI installed a benchmark. The bearing end of the benchmark was approximately 35 feet below grade. D. LABORATORY TESTING Samples were examined at our laboratory by the project geotechnical engineer. Selected samples were subjected to laboratory tests under the supervision of this engineer. A brief discussion of these results is provided below. The dry unit weights, moisture contents, liquid and plastic limits of the selected soil samples were measured. These tests were used to evaluate the potential BCI Project 04-089 Proposed Glass Residence Page 3 volume change of the different strata as an indication of the uniformity of the material and to aid in soil classification. To provide additional information about the swell characteristics and evaluate volume change characteristics of these soils (at their in-situ moisture conditions) total soil suction tests and absorption swell tests were performed on selected samples of the clay soils. Unconfined compression and hand penetrometer tests were also performed on selected undisturbed samples of the clay soils. These tests were performed to evaluate the strength and consistency of these materials. Consolidation properties of one soil sample were obtained by performing one- dimensional consolidation tests. A consolidation test was performed on a soil sample retrieved from Boring B-1 at a depth between six to seven feet below grade. The void ratio — pressure curve (e log p curve) for this soil sample is located in Figure 14. E. EVALUATION OF SITE INFORMATION Based on information received from Mr. Ron Kelm, P.E. with Forensic Engineers, Inc., the residential lot is approximately 115 feet wide and 330 feet long. The residential pad is approximately 80 by 80 feet. The approximate location of the residential pad with respect to the lot is reproduced in Figures 1 and 2. A rather large drainage ditch borders the south perimeter of the residential lot. The proposed foundation system is reportedly to be construction approximately 4 to 5 feet above existing ground level. I. General Soil/Geologic Conditions The property is located at 9221 Elizabeth Road in Houston, Texas. Based on the Geologic Atlas of Texas and our experience in the local vicinity, the site is situated within the Beaumont Formation. The Beaumont Formation typically consists of surficial clay and mud of low permeability, high compressibility, high to very high shrink/swell capacity, low shear strength and high plasticity. Based upon the USDA Harris County Soil Survey, this site is situated on the Addicks-Urban land complex. The following information is based upon the USDA BCI Project 04-089 Proposed Glass Residence Page 4 Harris County soil survey, and should be considered generally indicative of the type of soils and the range of engineering properties noted for this area and at this site, and should be used only as an indicator of the soil properties at this site. The surface of the Addicks-Urban land complex is plane to slightly convex with 0 to 1 percent slopes. This surface layer of the Addicks soil is friable, black loam about 11 inches thick. The next layer is friable, dark gray loam approximately 12 inches thick. Friable, dark gray loam with calcium carbonate and yellow to yellowish brown mottles is typically encountered at depth. This soil is poorly drained. Surface runoff is slow and permeability is moderate. The available water capacity is high. It is saturated with water for short periods during the year. The liquid limits and plasticity indices for this soil group ranges between 20-45% and 5-27%, respectively; the shrink-swell potential for the soil group, therefore, is low to moderate. II. Site Grading and Drainage Based upon visual observations and geotechnical exploration, no significant amounts of cut or fill were detected at this site at the time of our investigation. Boring B-2 encountered approximately 6 inches of fill sand. Figure 12 provides two photographs of general site information. As shown in Figure 12, the residential property is currently flat with no significant change in topography. For a more detailed description of the site grades, please refer to a limited topography map of the site performed by Godinich Surveyor's, LLC. III. Tree Survey Numerous mature trees are present within the residential lot. Figure 12 pictures the approximate size of these trees. Figure 2 — Tree Survey provides the approximate location of the documented tree trunks within the residential lot. As shown in Figure 2, a few trees may be removed during construction of the residential structure. Figure 3 — GIS Map of Site also provides an aerial view of the residential lot and house pad. As shown in Figure 3, the tree canopies generally cover the majority of the residential lot. Also, a pre-existing structure may have been present during this aerial photograph; however, the structure was not present during our investigation. BCI Project 04-089 Proposed Glass Residence Page 5 IV. Rainfall Data Figure 13 plots the monthly rainfall totals since 1998 at the National Weather Service (NWS) Houston/Galveston station located at the Hobby Airport. Monthly rainfall averages include observation recordings at the Hobby Airport, which is south of this residential structure. Rainfall totals and averages are based on the NOAA, NWS Web Site for the Hobby Airport area. Based on Figure 13, monthly rainfall totals during 1999 and 2001 are most likely considered rainfall extremes. As shown in Figure 13, yearly rainfall totals in 1999 and 2000 were comparatively below the yearly average. The majority of 1999 was considerably dry, particularly during the late summer and fall months, as indicated in Figure 13. A considerable amount of rainfall was recorded during June 2001 and August 2001. The year 2001 recorded approximately 30 inches of rainfall above the yearly average. Monthly rainfall totals were below average in January and February 2002. However, the monthly rainfall totals of 2002 were also well above the average, particularly for the months of July, August and October. The year 2002 recorded approximately 8 inches of rainfall above the yearly average. The year 2003 recorded approximately 5 inches of rainfall below the yearly average. However, during our site investigation, the months of January and February 2004 have been above the monthly average. Therefore, BCI concludes that our geotechnical/geophysical investigation in March 2004 was conducted during a relatively wet climatic period. F. SUBSURFACE CONDITIONS The subsurface conditions encountered in the borings are presented in Figures 4 and 5. Descriptions of the various strata and their approximate depths and thickness are shown in the Logs of Borings. A brief summary of the general stratigraphy indicated by the borings is given below. Depth refers to depth from the ground surface existing at the time of this investigation. References to depth should be made from this datum. I. Soil Stratigraphy Based upon site observations and the geotechnical borings, BCI is of the opinion that observed soil conditions are similar to those identified in the published geologic and soil information mentioned previously. In addition, Boring B-1 BCI Project 04-089 Proposed Glass Residence Page 6 encountered sandy fill soils in the upper six inches. The following paragraph provides a brief summary of the soils encountered within the geotechnical borings. For a more detailed description of the soils encountered, refer to the attached boring logs. The geotechnical borings generally encountered olive black, dark yellowish brown, to brownish black sandy lean clay to clayey sand. Light olive gray, dark yellowish brown to brownish gray lean clay with sand to sandy lean clay typically followed. A grayish orange, pale yellowish brown to yellowish gray lean clay with sand stratum was encountered next. At approximately 13 feet below grade, yellowish gray, light gray to grayish orange sandy lean clay was encountered in both borings. Boring B-2 encountered moderate yellowish brown, yellowish gray to grayish orange sandy lean clay beginning approximately 21 feet below grade. II. Water Observations The borings were advanced using a continuous flight auger. These drilling procedures allow groundwater seepage to be observed during and after drilling. Water seepage was observed at approximately 17 and 22 feet below grade during drilling operations for Borings B-1 and B-2, respectively. The water level remained constant in Boring B-2 after drilling operations. The bore hole caved in at 17 feet after drilling operations ceased in Boring B-1. The driller's log for Boring B-1 described the soil conditions below 20 feet as "flowing sands." The water levels may fluctuate at this site due to perennial rainfall totals and/or perched water seepage. Ill. Analysis of Geotechnical Borings a. Moisture Content Moisture content is defined as the ratio of the weight of water to the weight of dry soil in a given sample volume. Moisture content values are continuously recorded for every foot of soil. Figure 6 plots the moisture content profile for each geotechnical boring. As shown in Figure 6, the moisture contents ranged between 11 and 26 percent. BCI Project 04-089 Proposed Glass Residence Page 7 b. Consistency and Strength Tests BCI performed two test methods to further evaluate the strength and consistency of the retrieved soil samples. Hand penetrometers are used to measure the resistance to penetration of a soil. Typical hand penetrometer values range between 1.0 tons per square foot (tsf) and 4.5 tsf, with 4.5 tsf being the largest value able to be recorded on instrument. Figure 7 plots the hand penetrometer values for each geotechnical boring. The other test method is the unconfined compression test. This test is a special type of unconsolidated-undrained test commonly used for clayey type soils. Unconfined compressive strength tests provide a more accurate determination of the soil strength and consistency in comparison to the hand penetrometer values. The results of both these tests are located in the boring logs. The unconfined compressive strength values ranged between 1008 pounds per square foot (psf) and 4889 psf, indicative of moderate to very stiff soils. The lowest unconfined compressive strength value (1008 psf) was recorded in Boring B-1 in the upper one foot. As shown in Figure 4, this soil stratum is classified as clayey sand. Unconfined compressive strength testing indicates the cohesive properties of soils; it does not account for the shear strength characteristics of coarse-grained soils. Therefore, unconfined compressive strength values are typically lower for soils intermixed with fine-grained (clay, silt) and course-grained (sand, gravel) particles. c. Atterberg Limit Atterberg limits describe the consistency of soils (typically fine-grained soils) with varying moisture contents. Depending on the moisture content of a particular soil, the behavior of the soil can be divided into four basic states — solid, semisolid, plastic and liquid. Atterberg limits can also be important for the classification of a soil sample. Atterberg limits generally comprise of two tests called the plastic limit and liquid limit; however, a third test named the shrinkage limit can also be performed. The moisture content at the point of transition from a semisolid to plastic state is defined as the plastic limit. The moisture content at the point of transition from a plastic state to liquid state is defined as the liquid limit. BCI Project 04-089 Proposed Glass Residence Page 8 There are several indices that are derived from the Atterberg limits and/or moisture contents. Two of the more important indices are the plasticity index (PI) and liquidity index (LI). The plasticity index is the difference between the liquid and plastic limits. The plasticity index (PI) is the range over which a soil acts in a plastic state. Geotechnical studies have shown that the more plastic a soil (i.e., possessing a higher plasticity), the more compressive and expansive it will act. The PI values recorded at this site ranged from 9 to 19 percent indicative of low to moderate plastic soils. However, the moisture content of the soils relative to their plastic limits also play an important role in determining the volume change potential at various moisture states. The liquidity index scales the moisture content of a given soil relative to the Atterberg limits. If the liquidity index is negative, the soil will behave as a brittle material (solid to semisolid state) and is generally indicative of drier soil moisture conditions. If the liquidity index is between 0 and 1, the soil will behave as a plastic material and is generally indicative of wetter soil moisture conditions. If the liquidity index is greater than 1, the soil will behave as a liquid. Generally, as the liquidity index increases, the soil moisture conditions become increasingly wetter. Figure 9 plots the liquidity index (LI) for each geotechnical boring. Based on Figure 9, higher LI values were encountered in the upper three feet indicative of wetter soil moisture conditions in the upper strata. However, drier soil conditions were encountered between 3 to 7 feet based on lower LI values of -0.2 or lower. Boring B-2 encountered comparatively the highest LI values at deeper depths approaching 1.0, which corresponds to the documented water seepage at deeper depths. d. Total Soil Suction Total soil suction refers to the measurement of the free energy state of the pore- water exerted on the pore-water by the soil matrix. Where moisture content values describe how much moisture is in the soil, total soil suction describes where the moisture is going. In unsaturated soil conditions, soil moisture moves from a location of low suction to areas of high suction, otherwise stated, from a higher energy location to a lower energy location. Soil suction becomes the dominant force for soil moisture flow in unsaturated soil conditions and the gravity force component becomes comparably small. BC! Project 04-089 Proposed Glass Residence Page 9 The total soil suction values recorded at this site ranged from 3.36 to 3.68 pF, which are qualitatively described as low to near equilibrium total soil suction values. Figure 8 plots the total soil suction values for each geotechnical boring. Soil moisture tends to migrate from wets soils to dry soils, or from low total soil suction to areas of high to soil suction. Based on Figure 8, the total soil suction values are near equal within the upper 15 feet. e. Free Swell Tests Absorption free swell tests were also performed on 6 selected samples to evaluate the swell potential of these soils at their in-situ moisture and suction states. The swell tests performed on the soil samples at their respective overburden pressures indicate ranges of swells of -0.29% to 0.30%. The complete results of these tests are presented in Figure 10. The average swell value was approximately -0.06 percent, which indicates the lack of soil heave with the addition of free water. G. ELECTRICAL RESISTIVITY PROFILES Methods used to analyze and collect the field data, as well as interpretation of these geo-electrical moisture/material imaging resistivity (GMMIR) profiles is based upon a patented process, US Patent S/N 6,295,512. All rights reserved. Resistivity profiling is used throughout the mining, engineering and environmental fields to evaluate the moisture and material properties of rock materials. I. Geoelectrical Imaging Assumptions Two-dimensional subsurface objects are assumed in the inversion process which implies that the resistivity structure modeled is parallel to the profile and has some two-dimensional effects perpendicular to the profile. The resistivity technique allows for some limited "sight" or three-dimensional effects away from the exact profile line. The resolution of electrical resistivity methods decreases exponentially with depth. However, in the shallow subsurface, i.e., in the upper 100 feet of the earth, the resolution power of the resistivity method is good. Use of resistivity imaging BCI Project 04-089 Proposed Glass Residence Page 10 coupled with control information from borings including true resistivity measurements of the soil samples and the identification of stratigraphic boundaries and subsurface water seepage from site-specific soil borings greatly enhance the electrical resistivity tool. Electrical resistivity methods do not provide information regarding the density of the soil materials. Instead, they provide indications of the relative ease or difficulty with which electrical current passes through the soil and rock materials providing information regarding the moisture and material differences and resistivity contrasts at a site with depth. The purpose of the electrical resistivity profiling is to evaluate the variation of the subsurface and surficial expansive clay soils encountered at this site. II. Geoelectrical Computer Data Modeling Two-dimensional computer inversions were performed using a least-squares approximation to provide the "best fit" between the apparent resistivity field data and the assumed computer resistivity structure model. The electrical resistivity scale shown on the profile was truncated at 500 ohm-m to provide a uniform scale of resistivity values for comparison purposes. Actual resistivity values of the soils and/or materials in the red areas may be slightly greater than 500 ohm-m. Ill. Geophysical Exploration As shown on Figure 11, the color scales of Profile R1 range from "ice" blue to brown. The "ice" blue color represents the lowest resistivity values on the order of 1.5 ohm-m or less while the brown color represents the highest measured resistivity value on the order of 500 ohm-m. For discussion purposes of this report, BCI has outlined its terminology regarding the classification of the color scale shown on the resistivity profile: BCI Project 04-089 Proposed Glass Residence Page 11 0 to 3.0 ohm-m: extremely low 3.0 to 7.5 ohm-m: low 7.5 to 15 ohm-m: moderately low 15 to 30 ohm-m: moderate 30 to 50 ohm-m: moderately high 50 to 500 ohm-m: high to very high The following paragraphs summarize the relationship between these resistivity values (and the subsequent colors) and their respective soil types and moisture states. Resistivity values on the order of 3.0 ohm-m or less as shown by "ice" blue colors are usually indicative of wet to very wet soils with some possible associated water seepage. Based on the GMMIR profile, no extremely low resistivity values were encountered at this site. Relatively low resistivity soils (3.0 to 7.5 ohm-m) were recorded in each of the GMMIR profiles. Typically, these resistivity values are indicative of high PI clays and/or a soil regime having high moisture contents in relation to their corresponding plastic limits. Based on the soil conditions encountered, we are of the opinion that these low resistivity values are indicative of soils with their moisture contents above their respective plastic limit values. Moderately low resistivity values (7.5 to 15 ohm-m) are represented by green colors. Typically, these values represent a drier clayey soil regime having moisture contents at or lower than their corresponding plastic limits and/or lower PI clay materials with concentrations of sand, silt and/or gravel. Based on existing soil conditions encountered in Borings B-1 and B-2, moderately low resistivity values represent lower PI clay soils with sand and silt identified as sandy lean clay in the boring logs. Moderate resistivity values on the order of 15 to 24 ohm-m are represented by the yellow and orange colors. Considering the soil conditions at this site, resistivity values of this magnitude are indicative of more granular-type soils such as clayey sands. BCI Project 04-089 Proposed Glass Residence Page 12 Based on Profile R1, low resistivity values were encountered between moderately low to moderate resistivity values. These conditions were reflected in the geotechnical borings. No anomalous subsurface condition(s) are readily apparent in Profile R1. The moisture and material properties of the soil samples retrieved from the geotechnical borings does not appear to significantly deviate from the house pad based on Profile R1. H. ANALYSIS AND RECOMMENDATIONS I. Foundation System Options The active clays encountered at this site are subject to moisture related volume changes. The soils at this site were relatively dry to moist within the active zone based upon the March 17, 2004 geotechnical study. The dry state of the underlying clays could cause some upward movement with the absorption of free water. Various types of foundation systems currently are used for support of residential structures. The three most common types of foundation systems used in the Houston area are the following: • Type 1. Pier-and-beam foundations with deep drilled shafts founded below the zone of seasonal moisture variation and the with the floor system suspended above grade. • Type 2. Slab-on-grade foundation systems supported on drilled shaft extending below the zone of seasonal moisture variation. • Type 3. Slab-on-grade foundation systems that are supported in the shallow surface soils. Further, two perspectives of foundation design are inherent in these foundation systems. The first perspective, Mode "A", is the design of the slab-on-grade foundations from a soil-structure interaction standpoint to withstand excessive deflections, shear and bending moments. The second perspective, Mode "B", is the design of the interior floor systems and deep pier foundation systems in the BC' Project 04-089 Proposed Glass Residence Page 13 case for Type 1 or Type 2 to withstand these shears, moments and deflections. In each of these designs, compatibility between the interior and exterior cosmetic finishes and the foundation rigidity or flexibility must be considered. Obviously, some level of risk is associated with all types of foundation systems and a zero-risk foundation system does not exist. Further, post-construction homeowner maintenance of the foundations including, but not limited to maintenance of positive drainage around the house on all sides and the planting of vegetation no closer than its mature height to the foundation are essential for performance of all types of foundations and especially Type 2 and Type 3 foundations in Mode "A" design and in Type 1 foundations in Mode "B" design. This achievement of site equilibrium is the cornerstone of the PTI design, which assumes that the slab-on-grade foundation is affected only by climatic changes in the moisture addition and moisture subtraction in the soil and that the soils have achieved an equilibrium state with their surrounding climatic conditions. Each of above referenced systems is considered viable for various site conditions. In sites with potential near surface ground water or surface water seepage and/or sites with dry or highly expansive clays and deep fills, the surficial soils must be treated by replacement with more inert soils, injection with chemicals or water, and/or possible other drainage considerations before a Type 3 foundation system would be recommended. If these site conditions are not corrected prior to construction, then the Type 1 design is considered to be the most positive foundation option. Further, even with treatment of the soils, the Type 2 and Type 3 foundations must still be designed to withstand climatic fluctuations in moisture around the foundation and some movements are to be expected in these systems. In these situations, a Type 1 foundation will be the most positive foundation type from a geo-structural soil-structure interaction perspective (Mode "A"), and the other systems will inherently have more risk of differential movements due to soil- structure interactions. In situations were inert or low expansive soils or fills are present and concerns regarding downward movements or settlements exist, then the use of a Type 2 foundation may be most appropriate. BCI Project 04-089 Proposed Glass Residence Page 14 In BCI's opinion, the selection of the most appropriate foundation system for a given site is a function of many factors including, but not limited to: 1) the soil and rock conditions, 2) the climate, 3) the presence of vegetation, 4) the drainage and site topography, 5) the economics of the market, 6) customer requirements, 7) city or government requirements, 8) warranty company and mortgage company requirements and 9) the level of risk acceptable to the owners and developers for the project. II. Type 1 Foundation System BCI understands that a Type 1 design is currently being considered for this site. In addition, BCI understands that the finish foundation floor will be approximately 4 to 5 feet above current grade elevation to improve drainage conditions and lower the risk of flooding. All depths documented hereinto in this report are in reference to the ground elevation at the time of our investigation in March 2004. From a purely geotechnical soil-structure interaction perspective or Mode "A" design, Type 1 is the least risky foundation system. However, the Type 1 foundation system is subject to post-construction movement if the drilled piers are not stable and the wood elements are subject to moisture effects, which can lead to structural floor support issues unless proper drainage is provided in and around the crawl space of this system (Mode "B"). The active soils encountered at this site are subject to some moisture related volume changes. Any shallow or near-surface type of foundation system could be subject to some differential movements. Foundations for the proposed structures that are founded below the zone of seasonal moisture variations would be the most positive means of supporting the proposed structures. The pier-and-beam foundation system provides a structurally suspended floor slab supported above grade on drilled shafts extending below the zone of seasonal moisture variation. Based upon review of the total soil suction laboratory test results and the soil suction profile (Figure 8), we are of the opinion that a constant total soil suction value of 3.5 pF at a depth of 12 feet is reasonable for this site. The depth to constant suction will terminate within a lean clay with sand stratum as described in Figures 4 and 5. BCI Project 04-089 Proposed Glass Residence Page 15 a. Static Pier Analysis For a Type 1 foundation system, the following information is provided for general consideration and is accurate for the total boring depth of 35 feet which was scheduled for this site. The design parameters for proprietary piering systems and for depths below 35 feet should be further estimated and evaluated by the design structural engineer. In general, the total allowable resistance for a cast-in-place piling system is comprised of both end bearing and side resistance components. Depending upon the layering and soils present at depth, it is difficult to estimate at what pile deformation the individual components of end or side resistance will be mobilized. However, the rule is that some components of both the end bearing and the side resistance will be mobilized immediately upon loading and deformation. However, Vesic (1977) reports that it takes substantially less strain or deformation (on the order of 0.25 to 0.5 inches) to mobilize the side resistance component for piles regardless of pile size and length in contrast to the end bearing component mobilization of ultimate point resistance of a pile which requires a displacement on the order of approximately 10 percent of the pile tip diameter for driven piles and as much as 30 percent of the pile tip diameter for bored piles. Coyle and Reese (1966) indicate that in determining the load capacity of a pile, consideration should be given to the relative deformations between the soil and the pile as well as the compressibility of the soil pile system. The ultimate skin friction increments along the pile are not necessarily directly additive, nor is the ultimate end bearing additive to the ultimate skin friction or side resistance. Therefore, as a general rule, it is difficult to predict the soil-structure interaction for drilled piers or piles and a conservative approach should be taken by the design engineer with end bearing considered as a factor of safety. Based on the presence of water seepage at depths of approximately 17 to 22 feet below grade, cast-in-place piers should bear above the documented water table. Based upon the allowable bearing pressure equation for deep foundations, an allowable end bearing resistance of 3,500 pounds per square foot (psf) is calculated for piers bearing in the sandy lean clay stratum between 13 to 21 feet below grade using a factor of safety of 3. BCI Project 04-089 Proposed Glass Residence Page 16 Assuming the piers are bearing approximately 15 feet below grade with an end bearing pressure of 3,500 psf, based on the consolidation test, the primary consolidation settlement for these piers would be less than 1-inch. However, if the water table rises near the surface due to climatic conditions, the estimated primary consolidation settlement would be on the order of 1-1/4 inches. Based on soil types and loading conditions, BCI is of the opinion that some of the estimated consolidation settlement will occur during construction, or shortly thereafter. Based upon the allowable bearing pressure equation for deep foundations, an allowable side resistance of 450 psf is recommended for compressive loading and 325 psf is recommended to resist tensile uplift forces (using a factor of safety of 2) for piers bearing in the yellowish gray sandy lean clay stratum. These side resistance values should be used below the moisture and movement active zone, which in this case is estimated at 12 feet below existing grade. Depth of embedment will be reduced when considering the amount of dead load on the pier. Some caution should be used in application of dead load to reduce pier length and we recommend that the structural design engineer provide accurate estimates and bases for the dead load values used. Uplift resistance may also be derived from using an underreamed bell, which should be between 2.5 and 3 times the shaft diameter founded below the zone of seasonal moisture variation. The pier should be continuously reinforced to resist the soil-induced uplift loads and any other structural loads influencing the structure as dictated by the structural design engineer. The actual uplift resistance of the bell due to cohesive and friction modes of shear failure should be analyzed by the project structural engineer. Additional construction and design recommendations should be provided by the proprietary piering system manufacturer and the design structural engineer. b. Estimated Soil Induced Uplift Pressures The active clay soils encountered at this site will induce some upward forces on piers/piles placed at this site. Based upon our soil property correlations, assuming that the upper 12 feet of the soils are within the moisture and movement BCI Project 04-089 Proposed Glass Residence Page 17 active zone, we estimate that the uplift forces for piers/piles placed at this site will be approximately 800 psf acting uniformly around the shaft perimeter. c. Construction Considerations Concrete used for the shafts should have a slump of six (6) inches plus or minus one (1) inch and be placed in a manner to avoid striking the reinforcing steel and walls of the shaft during placement. Complete installation of individual shafts should be accomplished with an 8-hour period in order to help prevent deterioration of bearing surfaces. The drilling of individual shafts should be excavated in a continuous operation and concrete placed as soon as practical after completion of the drilling. No shaft should be left open for more than eight hours or overnight. Water seepage was encountered at approximately 17 to 22 feet below grade. The bore hole caved in at 17 and 21 feet below grade after drilling operations ceased. BCI recommends that the end bearing of the underreamed piers should be installed above these depths, if seepage does not allow construction, but not less than 15 feet. Due to the presence of water seepage, casing of the pier hole should be anticipated. If pier depths are less than 15 feet from existing grade, then BCI should be contacted to evaluate this effect on bearing and settlement. We recommend that the project structural design engineer be retained to observe and document the drilled shaft construction. The engineer, or his representative, should document the shaft diameter, depth, cleanliness, and plumbness of the shaft and the type of bearing material immediately prior to placement of the concrete. Significant deviations from the specified or anticipated conditions should be reported to the owner's representative and to the foundation designer. The drilled shaft excavations should be observed after the bottom of the hole is leveled, cleared of any mud or extraneous material, and dewatered, if necessary and immediately before placement of concrete. The pier excavations should be free of loose soil, ponded water or debris. If the structural engineer deems necessary, a void box may be installed underneath the grade beams. Based on the PVM values calculated at this site, the void box should have a minimum depth of 4 inches. BCI Project 04-089 Proposed Glass Residence Page 18 III. Type 2 Foundation System In situations were inert or low expansive soils or fills are present and concerns regarding downward movements or settlements exist, then the use of a Type 2 foundation may be most appropriate. Based on the soil conditions encountered at this site, BCI is of the opinion that a Type 2 foundation system would be a viable alternative to a Type 1 system. Type 2 foundation systems will allow upward movement but will help mitigate downward movement if the piers are designed and founded properly. Applicable design parameters for a Type 2 foundation system may be found in the sections labeled Type 1 Foundation System and Type 3 Foundation System. Inherent risks for slab-on-grade foundation systems are further discussed in the Foundation System Options section of the report. IV. Type 3 Foundation System The performance of these various systems is a function of the materials supporting them. Obviously, slab-on-grade foundations supported in the moisture active zone of the soil profile will potentially move differentially and behave differently than a completely suspend floor slab in Type 1 or by a pier supported slab as described by Type 2. Type 3 foundations are inherently subjected to more differential foundation movement; however, proper site preparation and appropriate structural design of slab-on-grade foundation systems allows their use in most circumstances. The owner should realize that a greater risk of movement is associated with a slab-on-grade foundation system, and some differential movements will occur through time. Control of these movements is a function of the maintenance of uniform moisture beneath and around the slab and proper placement of fill materials. The slab-on-grade design parameters provided in this report are based upon climatic effects only, and do not include the adverse affects of ponded water, previous or future trees, fill settlement, and utility line leaks or extreme moisture fluctuations due to capillary action of subterranean groundwater. Some differential movement of the slab should be anticipated during the life of the slab due to equilibration of moisture contents beneath the slab which prevents evapotranspiration of moisture from the ground. BCI Project 04-089 Proposed Glass Residence Page 19 The effects of the trees or ponding water near the foundation may be modeled, if they are considered as higher risk possible conditions. Every effort should be made by the structural design engineer and homeowner to discuss these issues and develop appropriate remedial schemes to address them prior to construction. If these adverse effects are considered to be likely based upon the final house placement location, grading issues and tree/vegetation issues, then BCI can help model their effects, if any. Please notify us in writing if these adverse effects are to be considered in our analysis and recommendations. If the differential movements and total movements outlined in this report are not acceptable, or if concerns over external environmental effects from trees, utility line leaks, fill settlement or groundwater fluctuations are considered a large concern, then we recommend using a Type 1 or Type 2 foundation system. a. Estimated Potential Vertical Movements The soils present at this site consist predominantly of lean clays with low to moderate movement potential. In general, the clays were dry to moist at the time of the field investigation and will possibly experience volume changes with fluctuations in their moisture content. The lightly loaded interior floor slab placed on-grade will be subject to potential movement as a result of moisture induced volume changes in the surficial clays. Potential Vertical Movement (PVM) calculations for various soil profiles at the site were performed using the Texas Highway Department's Method (TxDOT) TEX 124-E, soil suction testing and our engineering judgment and are summarized in Table 1. The PVM values presented below do not include the effects of differential movements from uncontrolled water sources such as poor drainage, utility line leaks or migration of subsurface water from off site locations. These movements are total vertical movements and do not consider differential swell between any two points on the ground surface. The potential vertical movement (PVM) values provided above are based upon the soil stratigraphy found in the boring logs. If final grades are changed ± 18 inches, then BCI should be notified in writing so BCI Project 04-089 Proposed Glass Residence Page 20 that we can review the effects of these grading changes upon the PVM values and other geotechnical issues. A reinforced (conventional rebar or post-tensioned) monolithic, slab-on-grade foundation system will need proper design and construction to resist and/or tolerate the moisture induced movements of the clays without inducing unacceptable distress in the foundation or superstructure. On the basis of laboratory tests and estimates of PVM, we recommend that the potential vertical movements (PVM) as outlined in Table 1 are used for slab design calculations at this site without any soil modification considering the cut and fill operations do not differ more than ± 18 inches from the available preliminary grading plans. These movements are total vertical movements and do not consider differential swell between any two points on the ground surface. If fills of more than 18 inches are contemplated with imported fills or with fills of higher plasticity indices than on-site soils samples in Borings B-1 and B-2, then BCI should be notified in writing so we can evaluate the impact of these fills, if any. b. Post-Tensioning Slab Design Parameters Design criteria for a slab designed in accordance with the Post-Tensioning Institute's (PTI) slab-on-grade design method have been developed. The PTI computer program (VOLFLO) was used to derive the PTI differential movements (ym). We recommend that the structural engineer consider the limitations of the VOLFLO program by noting that the PTI VOLFLO algorithm provides minimum design parameters for slab-on-grade foundation system design. The structural engineer's judgment and experience should also be used to design the slab-on- grade system to account for variations in conditions affecting ym and em values including review of the final grading plans to allow for construction over deep cut and fill sections where some settlements may occur. The edge moisture variation distances (em) for center lift and edge lift conditions were derived based on an Thornthwaite Index of +15 for the project site using the criteria provided in the PTI manual and other, more conservative methodologies. BCI Project 04-089 Proposed Glass Residence Page 21 The edge moisture variation distances provided below in Table 1 are based upon the PTI manual minimum guidelines. The PTI design parameters provided below are applicable if adverse site conditions have been corrected and soil moisture conditions are controlled by the climate alone (i.e., not improper drainage, unforeseen subsurface seepage, placement of uncontrolled or deep fills, vegetation influence or water leaks). The performance of slab and movement magnitudes can be significantly influenced by landscaping maintenance, water line leaks, and trees present before and after construction. The Post-Tensioning Institute (PTI) method incorporates numerous design assumptions associated with the derivation of required variables needed to determine the soil design criteria. The PTI design also assumes that the site possesses positive drainage directed away from the structure and that the slab perimeter moisture regime will be uniformly maintained during the useful life-cycle of the post-tensioned slab. Table 1. Recommended PVM and PTI Slab Design Parameters Boring Center Lift Condition Edge Lift Condition PVM from Edge Moisture Estimated Edge Moisture Estimated TxDOT Variation Differential Variation Differential Dry Distance em, ft Movement ym, in Distance em, ft Movement ym, in B-1 and B-2 1-1/2* 4.6 1.5 5.2 1.0 *on the order of Exterior grade and interior stiffener beams may be proportioned using an allowable soil bearing pressure of 2,000 pounds per square foot (psf) for beams placed in undisturbed natural soils. Exterior grade and interior stiffener beams may be proportioned using an allowable soil bearing pressure of 1,500 pounds per square foot (psf) for beams placed in properly compacted and monitored fill. We recommend that a field quality assurance soil testing laboratory/inspector observe the grade beam excavations prior to placing concrete. The foundation BCI Project 04-089 Proposed Glass Residence Page 22 bearing area should be level or suitably benched. It should be free of loose soil, ponded water and debris prior to the inspection. The PTI design parameters provided in Table 1 are based upon climatic fluctuations in the moisture conditions around the slab. More severe conditions such as ponded water standing around the slab and/or the presence of vegetation planted near the perimeter of the foundation are not considered in the above design parameters. Movement magnitudes approaching the PVM values in Table 1 are possible if severe drainage conditions, ponded water, or plumbing leaks are occur. As a result, the above PTI design parameters are contingent upon positive drainage and vegetation planted at least the mature height of the vegetation away from the slab perimeter and properly compacted fills placed beneath and around the slab perimeter. I. EARTHWORK GUIDELINES I. Site Grading Any future cut and fill operations should be supervised by a qualified testing laboratory. A set of general guidelines for additional earthwork required at this site are provided in Appendix 1 — Guidelines for the Placement of Controlled Earthwork of this report. Deep fill sections, other than minor fills produced during slab leveling of less than 6 inches, that will support the grade beams, should extend a minimum of 3 feet beyond the building line and then slope to natural grade on as flat a slope as practical or the fill section should be retained by a properly designed retaining wall. Generally, a maximum slope of 4 horizontal to 1 vertical is recommended. BCI should be contacted to provide additional recommendations if any slopes greater than 4 horizontal to 1 vertical or over 4 feet are planned within the project site so that slope stability analyses can be performed, if deemed necessary based upon the project specifics and upon written notification of the project structural engineer after final grading and design have been performed. If soft or compressible zones are identified during site grading and construction, or if obvious uncontrolled fill materials are noted between the boring locations within BCI Project 04-089 Proposed Glass Residence Page 23 the building pad areas, then these areas should be over-excavated and replaced with properly compacted on-site fill or select fill. II. Surface Drainage Proper consideration to surface drainage is essential to the performance of a monolithic slab-on-grade. The overall grading must provide for positive drainage away from the structure. All grades must be adjusted to provide positive drainage away from the structure. As a minimum, all grades and swales shall be constructed to meet FHA minimum standards. It is recommended that slopes of about 2 to 3 percent be maintained a reasonable distance away from the perimeter of the structures to ensure that positive drainage is provided around the structures. The drainage swales and grades should be maintained for the life of the structure by the homeowner. Water permitted to pond next to the structures can result in soil movements that exceed those indicated in this report. Roof drains should divert water well away from the structure. Sidewalks and other concrete flatwork may also be subject to movement. Flat grades should be avoided particularly adjacent to the slab-on-grade foundation. Areas around sidewalks or drives should be graded to prevent trapping and holding water adjacent to these facilities or the residential foundation systems. III. Compaction Recommendations Compaction requirements for the various material types may be summarized in Table 2. BC! Project 04-089 Proposed Glass Residence Page 24 Table 2. Compaction Recommendations for Various Materials Material Type Areas for Use Compaction to Recommended ASTM D698 at (x) of Thickness Optimum Moisture (in) as required Imported Fill Building Pad 95% at (0 to +5)%* for grade modification as required for On-site Fill Outside Building 95% at (-2 to +3)% grade Pad modification In-situ Soil Beneath all fill 95% at (0 to +5)% 6 inches Subgrade and pavements minimum *lf fill depths exceeds three feet in depth underneath the building pad, BC! recommends a minimum compaction effort of 98% of the maximum dry density according to ASTM D-698. BCI Project 04-089 Proposed Glass Residence Page 25 J. LIMITATIONS AND REPRODUCTIONS This geotechnical/geophysical Report is based on information supplied by the owner and/or others, and a visual survey of the elements exposed to Bryant Consultants, Inc. at the time of the field investigation. Bryant Consultants, Inc. will not be responsible for 1) knowledge of subsurface conditions substantially away from the borings and profiles 2) knowledge of cracks, or differential displacements that have occurred in a floor slab or flatwork without removing the floor covering and 3) any other element such as joists or beams and other structural members that are not readily visible by us. The boring and GMMIR profile locations were approximately determined by tape measurements from existing physical features. The locations and elevations of the borings should be considered accurate only to the degree implied by the methods used. Geophysical inverse methods are subject to errors and interpretation away from the profile line. Environmental errors may result in in-exact data which will provide some variation in the theoretical resistivity models after inversions of the same data sets. Non-uniqueness of the inverted data also may produce similar resistivity structure models using different raw data sets. Use of resistivity coupled with control information from borings including true resistivity measurements of the soil samples, identification of stratigraphic boundaries and the presence of groundwater greatly enhance the electrical resistivity tool. The conclusions and visual observations of this report are based in part upon the data obtained in the borings and upon the assumption that the soil conditions do not deviate from those observed. Any latent distress in areas not exposed cannot be anticipated without further destructive and/or intrusive testing. Unanticipated soil conditions are commonly encountered and cannot be fully determined by soil samples, test borings, or test pits. BCI further assumes that the conclusions drawn from this information are based in part on information gathered by others. Fluctuations in the level of the groundwater may occur due to variations in rainfall, temperatures, and other factors not present at the time the measurements were made. Samples obtained during the field operations will be retained 30 days after the issue date on the report. After this period, we will discard the samples unless otherwise notified by the owner in writing before the end of this period. The observations, discussions, recommendations and conclusions in this report are based solely on the geotechnical and geophysical explorations. If any additional information becomes available, then BCI reserves the right to evaluate the impact of this information on our opinions and conclusions and to revise our opinions and conclusions if necessary and warranted after review of the new information. The observed conditions are subject to change with the passage of time. This report does not constitute a guarantee or warranty as to future life, performance, need for repair or suitability for any other purpose at this site but as an evaluation only and that design and implementation of any repairs are responsibilities of others. Silence in this report regarding any environmental issues should not be a tacit assumption that the potential for environmental issues does not exist. Any environmental evaluation or investigation was beyond the scope of this report and should be performed by others, if warranted. This investigation was performed by Bryant Consultants, Inc. and the engineer in a manner consistent with that level of care and skill ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions. Unless otherwise indicated, this geotechnical report was prepared exclusively for Mr. Steve Glass. and expressly for purposes indicated by for Mr. Steve Glass. Permission for use by any other persons for any purpose, or by Mr. Steve Glass for a different purpose must be provided by Bryant Consultants, Inc. in writing. Any use made of this investigation and/or the conclusions and recommendations contained herein and any reliance thereon shall be specifically subject to the following limitation of liability: In recognition of the relative risk and benefits of the proiect to user and BCI the risks have been allocated such that user agrees, to the fullest extent permitted by law, to limit the liability of BCI to user for any and all claims, losses, costs, damages of any nature whatsoever or claims expenses from any cause or causes, including attorney's fees and costs and expert witness fees and costs, so that the total aggregate liability of the BCI to user shall not exceed five thousand dollars ($2,500.00) unless otherwise specifically agreed in writing. It is intended that this limitation apply to any and all liability or causes of action however alleged or arising, unless otherwise prohibited by law. For the purpose of this provision, BCI shall include the officers, directors, shareholders, partners, agents, servants and employees of BCI. This limitation is applicable to BCI's negligence or other fault in whole or in part. The reproduction of this report, or any part thereof, supplied to persons other than the owner, should indicate that this study was made for foundation design purposes only and that verification of the subsurface conditions for purposes of determining difficulty of excavation, traffic ability, etc., are responsibilities of others. Slope stability analyses are beyond BCI Project 04-089 Proposed Glass Residence Page 26 the scope of this project. These services may be performed at an additional cost upon your written request. Should you have any questions pertaining to any aspect of this report, or if we can be of further assistance to you, please do not hesitate to call on us. BC! Project 04-089 Elizabeth Road B-1 f Lot 6 R1 - Lot 4 Lot 5 Lot 7 Lot 8 0 O B-2 • • • 1 ci 0 I I I u Drainage Ditch NORTH GNMIR Profile and Boring Location Plan Note: Boring and GMMIR Profile locations are approximate. SCALE. -70 Bryant Consultants,Inc. 2033 Chenault Dr. figure Suite 150 project. 9221 Elizabeth Road Carrollton,Texas 75001 job no. 04-089 13RYANT Ph. (972)713-9109 Houston, Texas FAX(972)713-9171 by SMA insp. 3/17/04 Elizabeth Road • Lot 6 Lot 4 Lot 5 4 Lot 7 Lot 8 0 0 S S n; • S S S Drainage Ditch mm NORTH Tree Survey Note: Tree locations are approximate. SCALE: 1 =70 Bryant Consultants,Inc. 2033 Chenault Dr. figure Suite 150 project. 9221 Elizabeth Road Carrollton,Texas 75001 job no. 04-089 13RYANT Ph. (972)713-9109 Houston, Texas FAX(972)713-9171 by SM A insp. 3/17/04 N r s / . rte { 4 -K Legend Feet �_._._•.__.. 0 50 100 200 Harris County Soil Survey Ak - Addicks-Urban land complex Figure 3 - GIS Map of Site - Bryant Consultants, Inc. LOG OF BORING B-1 Dallas, TX Residence at Date Drilled 3/17/2004 'N=Standard Penetration Test 9221 Elizabeth Road Ground E+svai on ;Existing Grade "T=Moditled Cone Penetration Test Houston,Texas 77055 Casirg To NA BCI-04-089 Drilling Method Cont.Flight Auger Joe Glass f _.._�. t I LL l lB, 15 E m m ae ° is © . o . I ° q� C c {j p. V .� C © M rn t4 •� p Q „J of r �. U E 1" L•Depth n Q 9. a3 DESCRIPTION ' D -V U = .� - .- • ` teat c v) 5 2 o $ a`.. CL n a i w ` a U) ai Stiff Olive Black,Brownish Black to Dusky 17 106 30 16 14 48 145 1.0 18.9 1008 113.9 i Yellowish Brown CLAYEY SAND with occasional 19 2,5 '_ 2– iron ore nodules and roots. 3— Very Stiff Dark Yellowish Brown,Brownish Gray 18 108 35 18 = 19 76.4 17.3 3.54 2.25 2610 15.0 to Dark Yellowish Brown LEAN CLAY with sand, 16 3.75 12,6 '\occasional iron ore nodules,black inclusions and 1 13 30 16 12 3,46 4.5+ 5 \roots. 1 13 4.5+ 6 Stiff to Hard Pale Yellowish Brown,Yellowish Gray 1 i _ to Dark Yellowish Brown LEAN CLAY with sand, 17 3.36 1>25 12,2 7 occasional to few calcareous&iron ore nodules 20 110 1,25 1943 15.0 B and black inclusions. 1$ 29 16 13 74.0 18,1 3.50 2.5 9.6 21 1,0 g 10 • 11 1 , I 1 tL ,,i otikd 13 a Hard Yellowish Gray,Pinkish Gray to Grayish : 14 Orange SANDY LEAN CLAY occasional iron ore 15 118 33 1E 17 68.8 18.8 345 4.5+ 12.6 3992 15.0 .w 15 nodules and iron staining. =' 7. 16 , 17 -_- 18 19 30..r NI 16 115 3.69 4.5+ 10,7 4889 10 s Driller log described stratum as'Ftowing Sand'. I -S, 21 Recovery of soH sample riot possible. l 22 I { 23 i n 2't •N_13 3 25 26 27 ` ( I 28 t 1 w, 29 I { I I H 30 1 l 8 31 ` , 32 r 33 I 1 341 = 5 Boring Scheduled to and Terminated at 35 Feet. 36 a 37 Note:Water seepage encountered at 17 feet during l 38 drilling operations.Bore hole caved in at 17 feet. 39' Figure 4 —`� 40 Bryant Consultants, Inc. LOG OF BORING B-2 Dallas, TX I Residence at Date Drilled 3'171200.1 'N=Standard Penetration Test 9221 Elizabeth Road Ground Elevation Existing Grade "T Modified Cone Penetration Test Houston,Texas 77055 Casing To NA BC1-04-089 Drilling Method Dont Flight Auger --,.__T.-.. . Joe Glass d, v ° --E Q G o 0 p > ci t to T m 0 a7 : '� C � N N = y '0 Q. b E J w y tl C rn Depth ' - o DESCRIPTION y y c ` E § 0 a ,,,,to a 5 c feet ch Fl to 2 n a ©. a d 9Q. !� I w o t u.. 0 \Grayish Orange SAND(FILL). /1 23 104 1,75 1780 13.9 1 Very Stiff Dark Yellowish Brown,Brownish Gray 18 32 15 17 68 3.48 2.5 11.8 i 2 to Dark Yellowish Brown SANDY LEAN CLAY with 1 15 115 2.75 3459 8.0 3 \occasional iron are nodules and rootlets_ 4 Very Stiff to Hard Light Olive Gray,Yellowish Gray 15 34 18 16 68.5 18.0 3.46 4.5+ 12.9 5 to Pale Yellowish Brown SANDY LEAN CLAY with 11 t 4.25 toccasional iron ore nodules and black inclusions, 12 25 15 10 69.3 16.4 3.4914.5+ 6 ,x Stiff to Hard Yellowish Gray.Light Olive Gray to 14 3.75. 16.8 1 7 Grayish Orange SANDY LEAN CLAY with 1 occasional to few calcareous&iron ore nodules 17 i 347 3.0 8 nd black inclusions. j 18 114 I 77,9 19,7 2.25 10.7 2879 14.9 9 Very Stiff Grayish Orange,Light Gray to Dark 17 34 17 17 3.46 2.5 2 10 Yellowish Orange LEAN CLAY with sand. .. i 11 4, occasional iron ore nodules and iron staining. 1 12 13 Stiff to Very Stiff Yellowish Gray,Light Gray to 1 1 14 KO ii. Grayish Orange SANDY LEAN CLAY with 19 114 3.48 1.5 a 7.9 1199 t 14.9 g is ME occasional iron ore nodules and iron staining. d 17 a 18 1 I 19 2fl me 19 ,112 28 17 11 54 3.43 4.25 11.7 3297 9.5 1• 21 r Moderate Yellowish Brown,Yellowish Gray to • '2 '� Grayish Orange SANDY LEAN CLAY with 23 or, occasional iron ore nodules and iron staining ▪ 24 0 'N=20 26. ` 25 19 1 9 63 E 3 25 - - 1 Boring Scheduled to and Terminated at 25 Feet. _ 25 .. 27 Note:- Seepage water encountered at 22 feet 28 during drilling. Water level was approximately 22 e feet after 2 hours and boring caved at 21 feet at L 29 completion. Ji 30 Z 31 X 3' 32 it 33 x 34 ,. 35 j `, 35 1 ti ;i 37- 38H Figure 5 71 39- __ 40-i O M Co N \\\\\) N - N N O I.i. CO a> U a) f CNI m m O fT G � N O LL "° 1- CO N O O LO O Id) O C'7 N N `;uawo3 aJn4siow 0 co co N CD N 1 N N N N I a) O N • 0. 2 — N CL m co co 2 1 TI co 4,4 . 1 O r Q L CV Q CD ,--a lES C N CC 2 -...iiiimiwir i c ijj cn LL pp. i MM ar W 1 1 } - N I I p C? U') O in O O O In O 6 d' 4 c7 M N N r O O p 1. `Jalauaoa4aued PUSH 0 co N co N ,a. N N N N — N a) 0 N L m co co c f i 1 0 a-+ CO V r = t U) ' .O Q U) CU 0 N I CO o E O 0, i N-- LL - co 4 P . .4_ - N I 0 O 0) CO f` CO ( CO N O d' CO CO cO CO CO CO CO CO CO CO Ad `uo!}onS I!oS Ielol ct W W o F- -- co cr 1 oo N i _ co 1 N _ N N N cv m*NN''s:s''sssi\ m m 1 0 N CD f III N I ' co° co I a. X I co 1 co C 1 m I C" 1 I N J I r- Cii I CD o sf it 1 1 - 00 1 1 - co . 1 1 1 OVII - N I I I I 0 O CO co Nr N O N V• co co O O O O O O O O O O i I xapul kT1pinbil FIGURE 10. SWELL TEST RESULTS BCI Project Number 04-089 PRE-SWELL FINAL PERCENT BORING DEPTH ATTERBERG LIMITS MOISTURE MOISTURE LOAD VERTICAL NUMBER (ft) LL PL PI CONTENT CONTENT (psf) SWELL B-1 4.-5 30 18 12 12.9 13.7 562.5 0.10 B-1 8.-9 29 16 13 17.2 17.7 1062.5 -0.29 B-1 14-15 33 16 17 15.1 16.0 1812.5 -0.15 B-2 3.-4 34 18 16 14.9 15.9 437.5 0.30 B-2 5.-6 25 15 10 11.7 12.5 687.5 -0.20 B-2 9.-10 34 17 17 16.9 17.4 1187.5 -0.10 Average -0.06 Min -0.29 Max 0.30 Std. Dev. 0.22 PROCEDURE 1. SAMPLE PLACED IN CONFINING RING, DESIGN LOAD (INCLUDING OVERBURDEN) APPLIED, FREE WATER WITF SURFACTANT MADE AVAILABLE, AND SAMPLE ALLOWED TO SWELL COMPLETELY. 2. LOAD REMOVED AND FINAL MOISTURE CONTENT DETERMINED. Figure 11. GMMIR Profiles, Proposed Glass Residence BCI Project 04-089 Survey Date: 3/17/04 500.0 200.0 150.0 100.0 B-2 50.0 39.0 _ 36.0 E imm-1- �./� 33.0 ;! _ ~ _ _ _ 30.0 -2 __ /'� ■_ k 27.0 3- > s 24.0 -4_ \ 21.0 'uNi 18.0 °) mil-6 mo_ - 15.0 To 12.0 .6 4 6 8 10 12 14 16 18 20 22 24 26 28 30 =9.0 m Profile R1. East to West direction across the Lot. 7.5 w p 6.0 mni 4.5 al 3.0 mullm 2.3 ® 1.5 0.0 Notes: 1. Data at lower corners is interpolated. 2. Structure,Boring and Vegetation positions are approximate. 3 Patent Process,All Rights Reserved. US Patent S/N 6,295,512. j ,�r "' F € mow.'°�c 7 '"4 Y' '' y . �°' , .p - � = It E t . # 4 `"' s a L a t.tk..a. 5,`i. .. c 4•,,,,,, 4 1 �� s` , 5 5 ski y ir R' .=. .7. ,\4.'s,„Ta ,!N� "...,—*„:.-.,4‘.i'''''..;$,,,.,. 'S .z., ;lv, f pia; .,.` ,, �„.'v' 3.^ rt '0.d( ai , z..: x"i:-..- °.,'..7 - , C*. ,-...°!' e `� � ��q'' •�� � ^ a����'0..e'kR ;:tt !i^v»'�z, .d', yp,,,, - � �,�.. :p r R '• f a. «r y►-r"'* c x" _3^ i. w n,, "24'+' a.'r..n . � .rte P-- .�-a,� a _ � E .4-� View of residential lot viewing towards the N direction. iak* r # � g ,- - i z I`.u� i w ,r-7:-6 r °r ..::',1°,,,,,--*!"i, ' 4., ',-.1- I if ' - L° ,,,,-.4 '''''''',' '-..,; -,-'-':air weS tea.+. ° a n . ,, 1 p, ,� � ; "3,44%` x -, :7„ s & #.; m �;. :'a4. Vi. °' a, s P s .`"' �'.'rif�•.w�c•" �' � tea: , t� -- �A. q° a 4 ��„mac �«�."�. � .w »" s � x+rt .n„��� .-` `.°` -'.` ice i ;.:� r",s f�E,rwa � . <.wE+.."S .�� ���,�,�e .���„,�„'��.„„�� ����� .��: �,zf.�. ''',',0,,its* r � Fes, ,.��� '� :11,0,',`,-,4„. `��w. a" �`'•� 4'°, '� '�wM° r aye '�„ .�g;ar � ;' ' •w .: .'"I'.. '- vo . +. ,,, ' y ''`c .'`',. ,: •°S a: u "r ''''.44„ View of the approximate location of the residential house pad. Figure 12: Photographic Survey of Proposed Glass Residence a) C) 1- C") (N 0 0) 00 0 0 0a4 0000) 0) Q) 000000) 0) > NNNNN � - �- Q I noN PO Tdas _ 6ny 0 ..- Ainf o co aunt CtS C re ady El Jen gad uer LC) 0 LO o LO o N N (u!) Iielu!e. 0 emmv o I i 1 II i � i r , , l'' '-' ' 9- K A I a., ■ cts r ..„,..,,.,,,,, ,„, ,..,. , ,Ii..44;_ ,,,..., L I a cu a) W ■ au I , I I 1 ■ I II O O o O N O Ln o N O O M O Le)O M O O o Ls) V O O O o Or O of e8 P!°A APPENDIX 1 - GUIDELINES FOR THE PLACEMENT OF CONTROLLED EARTHWORK at GLASS RESIDENCE HOUSTON, TEXAS PREPARATION OF SITE This item shall consist of guidelines for the preparation of the site for construction operations by the removal and disposal of all obstructions that would impede the steady and continual progression of work at this site as described in the following paragraphs. Such obstructions shall be considered to include all abandoned structures, foundations, water wells, septic tanks, fences and all other trash and debris that have been placed on the site. It is the intent of this guideline to provide for the removal and disposal of all obstructions not specifically provided for elsewhere by the plans and guidelines. CLEARING OF AREAS TO BE FILLED All trees, stumps, brush, roots, vegetation, rubbish and other objectionable matter shall be removed and acceptably disposed of. Any depressions or low areas resulting from the removal of the above items or any soft spots encountered during the site preparation should be backfilled with approved material and compacted in accordance with the grading recommendations given below. All these roots of the removed trees should be removed in the building pad are to a depth of at least 2 feet below final beam depth. All vegetation shall be stripped from proposed fill areas and exposed soil surfaces shall be scarified to a depth of at least 6 inches. If fill must be constructed where the slope of the existing ground exceeds 4H:1 V, the existing ground surface should be benched with a series of horizontal terraces prior to fill placement. The benches should extend through any uncontrolled fills, or loose surface materials into hard natural ground. The fill should be placed and compacted with the compaction equipment working perpendicular to the fall line of the slope. Filling should start at the lowest portion of the slope and progress upward. Appendix I Page 2 It is the intent of this guideline to provide a loose surface with no uneven features which would tend to prevent or impend uniform compaction by the equipment to be used. COMPACTING AREAS TO BE FILLED After the foundation subgrade for the fill has been cleared and scarified, it shall be disked or bladed until it is uniform and free from large clods, brought to the proper moisture content, and compacted to not less than 95 percent of maximum dry density according to ASTM D-698 and as specified for on-site fill in Table 2. FILL MATERIALS Materials for fill shall consist of soils confined with the limits of the proposed development area, or imported soil similar to those present in the area. The soil shall be free from vegetation, roots, trash and other deleterious matter. Any imported fill materials should have a liquid limit less than 35%, plasticity index less than 18%, and percent clay less than 30%. Where fill materials contain rock fragments, the maximum size acceptable shall be four (4) inches. No rocks will be permitted within twelve (12) inches of the finished grade. It is the intent of this guideline that the rock fragments be mixed with sufficient soil binder and smaller rock fragments to allow for proper compaction and to prevent voids in the fill. If off-site borrow materials are used, we recommend that these materials are similar to those present in this area. DEPTH AND MIXING OF FILL LAYERS The fill materials should be placed in level, uniform layers which, when compacted, shall have a moisture and density conforming to the stipulations called for herein. Each layer shall be thoroughly mixed during the spreading to insure the uniformity of each layer. The normal compacted layer thickness shall not exceed nine (9) inches. MOISTURE CONTENT Prior to and in conjunction with the compaction operations, the moisture content of each layer and the subgrade shall be adjusted to be not less than the optimum determined by ASTM D-698. Where significant rock size particles (4 inch Appendix I Page 3 maximum size) exist in the fill, some deviation from the recommended moisture contents may be allowed by the field quality assurance soil testing laboratory/inspector. The graded building pads should be kept moist and not allowed to dry below the optimum moisture according to ASTM D 698 during the intervening period between the completion of the pad and the construction of the concrete slabs-on- grades. AMOUNT OF COMPACTION After each lift (layer) has been properly placed, mixed and spread, it shall be thoroughly compacted to not less than 95 percent of the maximum dry density as determined by ASTM D-698. In any area where fill heights exceed three (3) feet, compaction of layers below this depth shall be to a minimum density of ninety-five (98) percent of maximum dry Proctor density as determined by ASTM D-698. COMPACTION OF FILL LAYERS Compaction equipment shall be of such design it will be able to compact the fill to the specified density. Compaction of each layer shall be continuous over its entire area. SUPERVISION AND DENSITY TESTS All fill shall be placed under the supervision of qualified technicians working under the direction of the project geotechnical engineer. Field density and moisture content determinations shall be made on each lift of fill with the number of tests on each lift to be determined by the field technician and the field quality assurance soil testing laboratory/inspector. Low fills, less than three (3) feet, may be controlled with periodic visits to the site to perform tests on each lift of fill. Deeper fill sections will require full time supervision. Appendix I Page 4 REPORT Upon completion of the various fill sections, the project soils engineer shall provide copies of all field tests and a statement that the fill was placed in general agreement with the guidelines. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 1 of 42 FOUNDATION DESIGN OPTIONS FOR RESIDENTIAL AND OTHER LOW-RISE BUILDINGS ON EXPANSIVE SOILS by The Structural Committee of The Foundation Performance Association wvirw.foundationperformance.orq Houston, Texas Document # FPA-SC-01-X (DRAFT) ISSUE HISTORY (Only includes issues outside the Structural Committee) Rev Date Description Subcommittee Subcommittee # Co-Chairs Members A 27 Jan 00 First Issue George Wozny Ron Kelm V 25 Mar 04 For Committee Comments Michael Skoller Bill Polhemus X 1 Apr 04 For FPA Peer Review Lowell Brumley Jon Monteith Mari Mes George Cunningham John Clark Toshi Nobe Nicole Wylie Denis Hanys Jim Austin FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments - Foundation Performance Association-Structural Committee Page 2 of 42 PREFACE This document was written by the Structural Committee and has been peer reviewed by the Foundation Performance Association (FPA). This document is published as FPA-SC-01 Revision 0 and is made freely available to the public at www.foundationperformance.org so all may have access to the information. To ensure this document remains as current as possible, it may be periodically updated under the same document number but with higher revision numbers such at 1, 2, etc. The Structural Committee is a permanent committee of the Foundation Performance Association. Please direct suggestions for improvement of this document to the current chair of the Structural Committee. If sufficient comments are received to warrant a revision,the committee will form a new subcommittee to revise this document. If the revised document successfully passes FPA peer review, it will be published on the FPA website and the previous revision will be deleted. This document was created with generously donated time in an effort to improve the performance of foundations.The Foundation Performance Association and its members make no warranty regarding the accuracy of the information contained herein and will not be liable for any damages, including consequential damages, resulting from the use of this document. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 3 of 42 TABLE OF CONTENTS 1.0 INTRODUCTION 5 2.0 PROBLEM DEFINITION 6 3.0 GENERAL DESIGN CONSIDERATIONS 7 4.0 FOUNDATION SYSTEM DESIGN OPTIONS 7 4.1 DEEP SUPPORT SYSTEMS 8 4.1.1 Isolated Structural Systems with Deep Foundations 8 4.1.1.1 Structural Slab with Void Space and Deep Foundations 8 4.1.1.2 Structural Floor with Crawl Space and Deep Foundations 11 4.1.2 Stiffened Structural Slab with Deep Foundations 13 4.1.3 Stiffened Non-Structural Slab with Deep Foundations 14 4.1.4 Non-Stiffened Slab-on-Grade with Deep Foundations 15 4.2 SHALLOW SUPPORT SYSTEMS 15 4.2.1 Grade-Supported Stiffened Structural Slab 16 4.2.2 Grade-Supported Stiffened Non-Structural Slab 17 4.2.3 Grade-Supported Non-Stiffened Slab of Uniform Thickness 18 4.3 MIXED DEPTH SYSTEMS 19 4.3.1 Mixed Depth System for All-New Building Construction 19 4.3.2 Mixed Depth System for Building Additions with Deep Foundations 20 4.3.3 Mixed Depth System for Building Addition with Shallow Foundations 20 5.0 FOUNDATION COMPONENT DESIGN OPTIONS 21 5.1 DEEP SUPPORT COMPONENTS 21 5.1.1 Drilled and Underreamed Concrete Piers 21 5.1.2 Drilled Straight-Shaft Concrete Piers 23 5.1.3 Auger-Cast Concrete Piles 24 5.1.4 Displacement Piles 25 5.1.5 Helical Piers 26 5.2 SLAB AND GRADE BEAM REINFORCING 27 5.2.1 Post-Tensioned Reinforcing 28 5.2.2 Deformed Bar Reinforcing 29 5.2.3 Welded Wire Fabric Reinforcing 30 5.2.4 Fiber Reinforced Concrete 31 5.2.5 Unreinforced Concrete 31 5.3 VOID SYSTEMS UNDER GRADE BEAMS AND PIER CAPS 31 5.4 VAPOR RETARDERS 32 FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 4 of 42 5.5 GRADE-BEAM-TO-PIER CONNECTIONS 32 5.5.1 Grade-Beam-to-Pier Connections with No Restraints 32 5.5.2 Grade-Beam-to-Pier Connections with Horizontal-Only Restraints 33 5.5.3 Grade-Beam-to-Pier Connections with Horizontal and Vertical Restraints 33 6.0 FOUNDATION SITE DESIGN OPTIONS 34 6.1 MOISTURE CONTROL SYSTEMS 34 6.1.1 Site Drainage Systems 34 6.1.1.1 Site Grading 34 6.1.1.2 French Drains 34 6.1.1.3 Area Drains 35 6.1.2 Moisture Retarder Systems 35 6.1.2.1 Horizontal Moisture Retarders 36 6.1.2.2 Vertical Moisture Retarders 36 6.1.3 Watering Systems 36 6.1.3.1 Sprinkler Systems 37 6.1.3.2 Soaker Hose Systems 37 6.1.3.3 Under-Slab Watering Systems 37 6.1.3.4 Drip Watering Systems 38 6.2 VEGETATION CONTROL SYSTEMS 39 6.2.1 Root Retarder Systems 39 6.2.1.1 Vertical Root Retarders 39 6.2.1.2 Horizontal Root Retarders 41 6.2.2 Root Watering Wells 41 6.3 TREE AND PLANT SELECTION 42 FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 5 of 42 1.0 INTRODUCTION The scope of this document is to provide guidance in the selection of design options for residential and other low-rise building foundations,typically called light foundations, which are founded on expansive soils. Low-rise buildings are defined as one to three stories in height and have masonry, wood, cement-board, or stucco exterior walls. These buildings include houses, garages, small apartment and condominium buildings, restaurants, schools, churches,and other similar structures.Design options for foundation systems, foundation components, and moisture and vegetation control methods are reviewed and compared. There are no absolute design rules for choosing a design.This document provides a list of advantages and disadvantages for each of the many commonly used foundation design options to assist the designer in selecting the most suitable option The intended audiences for the use of this document are structural, civil, and geotechnical engineers, builders, architects, landscape architects, owners, and others that may be involved in the design or purchase of foundations and building sites that are located in the southeast region of the state of Texas, and primarily within the City of Houston and the surrounding metropolitan area. However, many of the advantages and disadvantages discussed for each of the foundation and site design options may also apply to other geographical areas with expansive soils. Geographical areas that potentially have foundation problems similar to those in the Houston area may be identified as those having large surface deposits of clays with a climate characterized by alternating wet and dry periods. A brief overview of the design problems associated with expansive soils is provided in Section 2.0, and general design considerations are presented in Section 3.0.The foundation design options are categorized into three separate sections. Section 4.0 covers foundation system design options considering the structural foundation system as a whole.The foundation systems are subdivided into two groups: deep support systems and shallow support systems. Section 5.0 addresses design options for various individual structural components of the foundation systems that are discussed in Section 4.0. Section 6.0 discusses design options for site moisture and vegetation control systems. Foundation design options for heavily loaded structures such as mid-to high-rise buildings or large industrial structures that usually require deep foundations or thick large mat foundations are not addressed.Nor are design options for lightly loaded structures that are not susceptible to significant damage due to differential vertical movements from soil moisture changes. Examples of these types of buildings include relatively flexible light gage metal buildings with exterior metal siding and roofing and wide open interior spaces with no interior partition walls. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 6 of 42 I 2.0 PROBLEM DEFINITION The challenge with designing building foundations on moderate to highly expansive clay soils is the potential detrimental effects of differential movements of the foundation structural elements due to volumetric changes of the underlying and surrounding soils. In simple terms, expansive clay soils swell and can cause heave when they become moist, and can cause shrinkage and can subside when they dry out. Movement of expansive soils is directly caused by fluctuations in the moisture content of the soil particles. Because homogeneous expansive clay soils have very low permeability, fluctuations in the moisture content of the soils might normally be expected to occur over a very long period. However, geotechnical phenomena such as ground faults, surface fractures due to desiccation of clays, and decomposition of tree roots cause fissures and cracks that become widely disseminated over time. Due to the repeated wetting, swelling, drying, and shrinking of the clay as it weathers,the fissures often fill with silt and sand, and create pathways for water that can speed up the infiltration process. Water can also spread easily through naturally occurring sand strata, sand seams, and micro-cracks in clay soil caused by previous shrinkage.High negative pressures in clay soils with low water content also increase the tendency for water to be suctioned into the clay. Environmental factors other than climatic conditions can also affect expansive soils. Water extraction by tree roots or other vegetation, a process known as transpiration, can cause soil shrinking. Swelling can be a result of water infiltration into the soil from lawn irrigation systems,broken water pipes, flooded and leaking utility trenches, bad drainage, or leaking swimming pools, or it can be a result of slow moisture replenishment and equalization after the removal of a tree. Other less common phenomena may also occur. The combined effect and variability of all of these possibilities make it very difficult to predict expansive soil ground movements. Foundation movements are considered problematic only if they result in negative phenomena that detrimentally affect the performance or appearance of the building. The negative phenomena is considered to be structural if the load carrying capacity of the superstructure or foundation elements are affected, or is considered to be cosmetic if only the appearance of the exterior cladding or interior wall, floor, or ceiling finishes are affected.Negative phenomena may also affect the serviceability the building, such as the opening or closing of doors, or as may occur to the building utilities or other services, such as piping or ductwork. Negative phenomena due to foundation movement typically occur because of differential movements between various parts of the building. Differential movements often lead to high internal stresses in building components that manifest into distress in the form of cracks, splitting, bending, buckling, or separations in the exterior cladding systems such as brick, cement-board panels, or in the interior finishes such as gypsum drywall panels,wood paneling, and flooring. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 7 of 42 13.0 GENERAL DESIGN CONSIDERATIONS Aside from supporting the building loads,the goal of the structural foundation design in expansive soil areas should be to economically minimize the detrimental effects of foundation movement.This can be done by either isolating elements of the foundation system from potential soil movements or by using design methods and details that help to control the effects of the movement of the soil. Movements of expansive clay soils are generally restricted to an upper zone of soils known as the active zone. The lower boundary of this zone is commonly defined as the line of zero movement.The depth of the active zone usually varies from site to site. In the Houston area, this depth typically ranges from about 8 to 12 feet, but in some areas, it can be as much as 15 to 20 feet. The depth of the active zone is an important design parameter used in the engineering design of foundations on expansive soils, particularly when planning to use deep foundations. Another general consideration is the effect of the magnitude of surcharge pressure on the degree of swell that can occur. Lightly loaded foundation components, such as concrete flatwork,pavements, and building slab-on-grade floors, are much more impacted by expansive soil moisture changes than are heavily loaded foundation components such as heavily loaded bearing walls. Heavy loads reduce the amount of swell than can occur. Another goal of foundation design should be to maintain uniformity of bearing pressures as much as possible in order to reduce differential settlements. Various foundation system design options are available that meet these goals to varying degrees. Many options are also available in the design and selection of the components that make up these foundation systems;however,the choice shall be based upon an engineered geotechnical investigation.Different options are also available in the design of the site around the foundation and the selection of landscaping components.Advantages and disadvantages of these options are discussed in the following sections. 14.0 FOUNDATION SYSTEM DESIGN OPTIONS This section discusses the various types of foundation systems that are commonly used for residential and other low-rise buildings in the Houston area where expansive soils occur. In this document,the foundation system is considered to include the structural floor framing system at or near grade level and all other structural components underneath the building. The building superstructure consists of all structural elements above the grade level floor. The foundation systems are subdivided into two groups: deep support systems and shallow support systems. Each of these systems has an associated level of risk of damage that may occur to the building superstructure and architectural components due to differential foundation movements. Each of these systems also has an associated relative cost of construction. When comparing the various foundation systems,the level of risk is typically FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 8 of 42 found to be inversely proportional to the level of cost. Higher risks are often accepted due to economic considerations. For example, shallow support systems have a relatively higher level of risk than deep support systems, but are often selected due to economics and affordability. Because risk of damage and economic considerations are involved, building owners and/or developers need to be involved in the selection process of the foundation system. To assist in this selection,the foundation systems are generally listed in the order of increasing levels of associated risk and decreasing levels of construction cost. 4.1 DEEP SUPPORT SYSTEMS Deep support foundation systems are defined as foundations having deep foundation components such as drilled piers or piles that extend below the moisture active zone of the soils and function to limit the vertical movements of the building by providing vertical support in a more stable lower level of soil that is not susceptible to movements caused by moisture fluctuations. 4.1.1 Isolated Structural Systems with Deep Foundations Isolated structural systems are characterized as having a superstructure and a grade level structural floor system that are designed to be physically isolated from the effects of vertical movements of expansive soils.This is accomplished by providing sufficient space between the bottom of the floor system components and the top of the soil that will allow the underlying expansive soil to heave into the space or sink without causing movement of the floor system or imparting forces on the foundation components.The structural floor system usually consists of a reinforced concrete slab and series of grade beams, but other types of materials and framing systems may be used.A crawl space may be created by constructing the floor system a few feet above the ground, or a smaller space may be created by using a void forming system. 4.1.1.1 Structural Slab with Void Space and Deep Foundations Structural slab Void boxes S smug- Grade �_..— I In situ or beam cxlrer�=isc competent soil Deep foundation Figure 4.1.1.1 Structural Slab with Void Space and Deep Foundations FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 9 of 42 This foundation system typically consists of a structural reinforced concrete slab with cardboard carton forms that create a void space that separates the slab from the surface soils. The depth of the void forms ranges from four to eight inches and depends on the expansiveness of the soils. The more expansive the soil (i.e. the higher the plasticity index), the deeper the cardboard carton forms needed. The slab is called a"structural slab"because it spans between reinforced concrete grade beams that are supported entirely by deep foundations, similar to an elevated parking garage. Because of the relatively small void space that is used with this system,the bottom portion of the grade beams are normally cast directly on the soil, even though they are designed to span between the deep foundations. In the past, void cartons were commonly used beneath grade beams with this system. The slabs typically range in thickness from four to eight inches.The reinforcement may consist of a single or double mat of rebar. The structural slab is designed in accordance with the American Concrete Institute (ACI)publication,Building Code Requirements for Structural Concrete,ACI 318. Void forms serve as formwork for the placement of concrete by acting as a temporary platform that supports the weight of the wet concrete until the concrete sets. Void forms typically are made of corrugated paper arranged in an open cell configuration.The exterior surface is wax impregnated to temporarily resist moisture during concrete placement.The forms are specifically designed to gradually absorb ground moisture, lose strength, disintegrate over time, and leaving a void between the expansive soils and the concrete slab. If the soil below the concrete heaves, it can expand into the space created by the void form without lifting the foundation. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 10 of 42 TABLE 41.1.1 STRUCTURAL SLAB WITH VOID SPACE AND DEEP FOUNDATIONS ADVANTAGES* DISADVANTAGES* COMMENTS 1. Reduces vertical movements of 1. Usually results in higher 1. Slab is constructed about 4 to 8 inches slab-at-grade due to expansive construction cost. above grade using void carton forms. soils provided a sufficient void is 2. May require additional engineering 2. Slab is designed to span between maintained under slab and design effort than a slab-on-grade, grade beams.Grade beams are supporting deep foundations are and may result in higher engineering designed to span between deep founded sufficiently below active fees. foundations. zone. 2. Usually outperforms any other 3. Extra time required to construct 3. Slab is more heavily reinforced than type of foundation system. structurally isolated floor may non-structural slab. lengthen overall construction 4. Vapor retarders such as polyethylene 3. Reduces,but does not eliminate, schedule. sheathing should not be placed below need for a foundation 4. Improper carton form installation carton forms.Vapor retarders should maintenance program. may result in void that is insufficient be placed above carton forms in order 4. More rigid than a timber framed to provide for anticipated soil to allow moisture to degrade void floor with crawl space and deep expansion. boxes. foundations,resulting in less 5. Termites may be attracted to moist 5. Usually constructed with no carton differential movement of cardboard of carton forms. forms below grade beams due to superstructure. 6. Grade beams that are in contact with potential water infiltration into void 5. Allows a void under and down shafts of deep foundations. approximately 80-90%of soil may heave due to swelling of foundation when void cartons are expansive soils. 6. Installation of an expendable hard not used under grade beams. 7. Depending on slab elevation,may surface above carton forms such as allow water to collect below slab. Masonite sheeting will facilitate 6. No need for select structural fill. construction. Fill may be comprised of expansive or non-expansive soil. Fill need only be compacted to a density sufficient to support slab during setup. 7. Geoteclmical design parameters are more accurately defined than for shallow support foundation systems. *Compared to other foundation systems as described in Sections 4.1.1 to 4.2.3. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 11 of 42 4.1.1.2 Structural Floor with Crawl Space and Deep Foundations Block wall Structural floor or isolated `,,.. support with tillll Ni, Termite shield Crawl //g space IN Milli } Grade bc;ayn_____ In situ or • Deep foundation otherwise competent soil • Figure 4.1.1.2 Structural Floor with Crawl Space and Deep Foundations This foundation system is similar to the previous system, except that the vertical space used to isolate the floor system is much larger, usually at least 2_feet,which is sufficient to allow access underneath the floor, hence the name "crawl space". The structural floor system can be constructed utilizing any of the following common structural components: (a)wood subfloor and joists supported by wood, steel, or concrete beams; (b) concrete floor slab and joists supported by concrete beams;or (c) steel deck and open web bar joists or cold-formed sections supported by steel or concrete beams. Other combinations of these floor-framing components are possible, and other materials may be used such as precast concrete planks or T-sections. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 12 of 42 TABLE 4.1.1.2 STRUCTURAL FLOOR WITH CRAWL SPACE AND DEEP FOUNDATIONS ADVANTAGES* DISADVANTAGES* COMMENTS 1. Reduces vertical movement of 1. Usually results in highest 1. Ground floor is typically constructed slab-at-grade due to expansive construction cost. 30 to 42 inches above grade,but can soils,provided sufficient crawl easily be greater. space is maintained under slab 2. Requires more extensive design and supporting deep foundations effort,and will result in higher 2. Floor beams typically consist of steel, sufficiently below engineering fees. concrete,or wood beams spanning are founded suf between piers over a 12-30-inch high active zone. 3. Takes longer to construct because it is labor intensive. crawl space. 2. Usually outperforms any other 3. Also known as Post-and-Beam, type of foundation system. 4. Void below floor can collect water if Block-and-Beam,or Pier-and-Beam. 3. Reduces,but does not eliminate, nearby grade or other surrounding sites are at a higher elevation. 4. Flooring typically consists of wood need for foundation maintenance framing,steel framing,precast program. 5. Less rigid than a stiffened slab, which may allow more differential concrete planks,or precast double 4. Void cartons,sometimes tees. problematic in their installation, movement of superstructure,causing more cosmetic distress. 5. Crawl space should be ventilated to are not required. 6. Crawl space may allow sufficient evaporate moisture,which 5. No need for select structural fill. oxygen for roots to grow,which accumulates due to natural soil 6. Accommodates certain may cause soil shrinkage. suction,drainage problems,and architectural styles with raised plumbing leaks. first floors. 7. Proper drainage must be provided in crawl space. 7. Exposed below-floor plumbing is 8. Exposed below-floor plumbing may accessible. freeze. 8. More suitable for flood-prone areas since ground floor is generally higher than for other foundation systems. 9. Floor is easier to level than a slab- on-grade or structural slab with void space. 10.Helps to preserve nearby existing trees by allowing oxygen to root zones. 11.Allows a void under approximately 95%of foundation when void cartons are not used under grade beams,or nearly 100%when all beams are raised completely above grade. 12.Reduces settlement from soil shrinkage. 13.Geotechnical design parameters are more accurately defined than for grade-supported systems. *Compared to other foundation systems as described in Sections 4.1.1 to 4.2.3. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 13 of 42 4.1.2 Stiffened Structural Slab with Deep Foundations Stiffened Structural slab spans to grade beams grade. beams t,can st[itettirai tall In sltu of Deep other\tise foundation competent soil • Figure 4.1.2 Stiffened Structural Slab with Deep Foundations The stiffened structural slab with deep foundations is the same as the structural slab with void space and deep foundations with the following exception: the slab is placed, without a void, over the expansive soils and new fill, and the foundation must be designed to accommodate the pressures from the swelling soils. The foundation is designed as a"stiffened" slab.The grade beams form a grid-like or"waffle"pattern in order to increase the foundation stiffness and reduce the potential bending deflections due to upward movement of the foundation. Using continuous footings in a grid-like fashion helps to reduce differential deflections. The deep foundations are used to minimize downward movement, or settlement, caused by shrinking soils.The stiffened structural slab with deep foundations should be designed to resist heave in accordance with the BRAB 33 (Building Research Advisory Board), Wire Reinforcement Institute(WRI) publication,Design of Slab-on-Ground Foundations;the ACI publication,Design of Slabs on Grade, ACI 360R, or the Post-Tensioning Institute (PTI) publication,Design and Construction of Post-Tensioned Slabs-on-Ground. TABLE 4.1.2 STIFFENED STRUCTURAL SLAB WITH DEEP FOUNDATIONS ADVANTAGES* DISADVANTAGES* COMMENTS 1. Eliminates need for removing 1. Does not limit heave that may occur. 1. Slab is designed to span between existing non-compacted fill. 2. Requires additional design effort and grade beams. Grade beams are 2. Fill may be comprised of higher design and construction cost. designed to span between deep foundations. expansive or non-expansive soil. Fill need only be compacted to a 2. Slab is typically 4 to 8 inches thick, density sufficient to support slab beam spacing is less,and slab is more during setup. heavily reinforced than for stiffened 3. Reduces settlement from soil slab on fill. shrinkage. 3. Stiffening grade beams should be continuous. 4. Slab is more heavily reinforced than non-structural slab. *Compared to other foundation systems as described in Sections 4.1.1 to 4.2.3. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 14 of 42 4.1.3 Stiffened Non-Structural Slab with Deep Foundations Stiffened Son- lippol[t.'d ,1,11) z de beams Compacted structural fill In situ or 1)ccp - otherwise Blond ltion competent soil Figure 4.1.3 Stiffened Non-Structural Slab on Fill with Deep Foundations This type of foundation system is a stiffened concrete slab that may bear on non-expansive select structural fill,with the stiffening grade beams spanning to deep foundations. Select structural fill can be defined as sandy clays with a plasticity index between 10 and 20, and a liquid limit less than 40.The fill acts as a buffer zone between the expansive soils and the slab, reducing the potential differential movement of the foundation. The foundation is designed as a ribbed mat that is"stiffened"with relatively deep and closely spaced grade beams. The grade beams are laid out in a grid-like or"waffle"pattern and are designed with sufficient stiffness to reduce the bending deflection caused by shrinking or swelling soils. See Section 4.1.2 for additional design information. TABLE 4.1.3 STIFFENED NON-STRUCTURAL SLAB WITH DEEP FOUNDATIONS ADVANTAGES* DISADVANTAGES* COMMENTS 1. Usually less expensive than 1. Due to potential uplift forces,grade 1. Stiffening grade beams should be structurally isolated systems with beams may be deeper than those of a continuous across slab. deep foundations. structurally isolated system. 2. Select structural fill may be used to 2. Provides high stiffness without 2. Fill,if used,has to be field-verified reduce potential vertical rise. adding much concrete or for conformance to geotechnical reinforcement. specifications. 3. Settlement from soil shrinkage is usually less than that of shallow supported foundations. 4. Slab thickness and reinforcing is usually less than that of structurally isolated systems. *Compared to other foundation systems as described in Sections 4.1.1 to 4.2.3. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 15 of 42 4.1.4 Non-Stiffened Slab-on-Grade with Deep Foundations Grade beams below heavy walls and columns only i L (.t?1T1pdcted `: •IIUCtw.lrai lii) In situ or otherwise competent fill Deep foundation ,XJ Figure 4.1.4 Non-Stiffened Slab-on-Grade with Deep Foundations This system consists of a slab-on-grade with grade beams under load bearing walls supported by deep foundations. The foundation will move with the underlying soils. The foundation has little resistance to soil movement with this system. Perimeter grade beams are typically provided with this system to support the exterior wall system and to prevent undermining of the slab by erosion. They may also function as a root retarder or vertical moisture retarder. Interior grade beams are also usually provided under all interior load-bearing walls and shear walls. Interior columns are typically supported directly by deep foundations. TABLE 4.1.4 NON-STIFFENED SLAB-ON-GRADE WITH DEEP FOUNDATIONS ADVANTAGES* DISADVANTAGES* COMMENTS 1. Comparatively easy and quick to 1. Does not limit amount of vertical 1. Flat slab rests directly on underlying construct. movement that may occur. soil. 2. Typically has fewer grade beams 2. Does not limit amount of vertical 2. Warehouses are often constructed than stiffened slab foundation differential displacement that may using this method where interior slab systems. occur except for relatively small and movements can be tolerated. 3. Construction joints and isolation thick slabs. 3. Select structural fill may be used to joints may be used with this 3. Lack of grade beams makes it reduce potential vertical movements. system to allow separate concrete difficult to jack against if 4. Fill,if used,has to be field verified placements. underpinning is later required. for conformance to geotechnical 4. Slab may not provide sufficient specifications. stiffness for jacking if future underpinning is required. *Compared to other foundation systems as described in Sections 4.1.1 to 4.2.3. 4.2 SHALLOW SUPPORT SYSTEMS Shallow support foundation systems are defined as foundations having shallow foundation components that do not extend below the moisture active zone of the soils and are subject to vertical movements due to volumetric changes of the expansive soils. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 16 of 42 4.2.1 Grade-Supported Stiffened Structural Slab Grade beams are supported directly by the underlying soils ,Stiffened structural slab r s I Fill,need not he 1 comp[ii..tcd 1 > 6 Inches — In situ or otherwise competent soil Figure 4.2.1 Grade-Supported Stiffened Structural Slab This foundation system is similar to that discussed in Section 4.1.2, except that the grade beams are supported directly by the underlying soils instead of spanning to deep foundations. The key advantage of this system over that discussed in Section 4.2.2, is that as long as the grade beams penetrate a minimum of six inches into the competent natural soils or properly compacted fill. Fill placed between the grade beams is only required to be compacted enough to support the concrete during placement. TABLE 4.2.1 GRADE-SUPPORTED STIFFENED STRUCTURAL SLAB ADVANTAGES* DISADVANTAGES* COMMENTS 1. Compaction of new fill below 1. May experience more vertical 1. Also referred to as a ribbed mat or slab not as critical,and eliminates movement than stiffened slabs on "super slab". need for removing existing non- deep foundations. 2. Grade beams must be supported by compacted fill. 2. More expensive than slab-on-grade competent soils. 2. Usually performs better than other and non-structural systems due to 3. Slab is designed to structurally span grade-supported slabs. more concrete and reinforcement. between grade beams. 3. If fill below slab is loosely 3. Requires more design effort than 4. Slab is typically 4 to 6 inches thick, compacted,potential vertical rise non-structural slab systems. depending on beam spacing. may be reduced as compared to 4. Experiences more vertical other grade-supported movement than deep1 supported 5. Grade beams may be wider or more foundations. y pp closely spaced than other grade- systems. supported slabs. 4. Faster to construct than slabs with 5. Does not prevent foundations from deep foundations. tilting. *Compared to other foundation systems as described in Sections 4.1.1 to 4.2.3. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low•Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 17 of 42 4.2.2 Grade-Supported Stiffened Non-Structural Slab Stiffened grade Grade su ported slab. beams �r_ t ,miTieled strt�ciaial fiill � �� I In situ or otherwise competent soil Figure 4.2.2 Grade-Supported Stiffened Non- Structural Slab This foundation system is similar to that discussed in Section 4.1.2, except that the grade beams are supported directly by the underlying soils instead of spanning to deep foundations. It is also similar to Section 4.2.1 except that the entire stiffened slab is supported by the surface soils that are susceptible to the seasonal moisture fluctuations and movement. The foundation is designed utilizing continuous stiffening beams that form a grid like pattern. Grade-supported stiffened slabs should be designed in accordance with the WRI publication, Design of Slab-on-Ground Foundations,the ACI publication,Design of Slabs on Grade,ACI 360R, or the PTI publication,Design and Construction of Post-Tensioned Slabs-on-Ground. TABLE 4.2.2 GRADE-SUPPORTED STIFFENED NON-STRUCTURAL SLAB ADVANTAGES* DISADVANTAGES* COMMENTS 1. Most economical system used 1. May experience more vertical 1. Stiffened slabs are sometimes called where expansive soils are present. movement than stiffened slabs "waffle"or"floating"foundations. 2. Faster to construct than slabs with supported on deep foundations. 2. Grade beams must be supported by deep foundations. 2. Does not prevent foundations from competent soils. tilting. 3. Most commonly used foundation system in Houston area. *Compared to other foundation systems as described in Sections 4.1.1 to 4.2.3. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 18 of 42 4.2.3 Grade-Supported Non-Stiffened Slab of Uniform Thickness Mat or slab of ulnitorm thicklie s omp,lci d .ti°ttc tot al till in situ or otherwise competent soil Figure 4.2.3 Grade-Supported Non-Stiffened Slab of Uniform Thickness This system consists of a concrete slab-on-grade of uniform thickness with no deep support foundation components.The slab may be supported on in situ soils or compacted fill.This foundation system should be designed by the PTI method or other methods to resist the potential bending moments induced by the differential deflections of the slab when subject to expansive soil movements. TABLE 4.2.3 GRADE-SUPPORTED NON-STIFFENED SLAB OF UNIFORM THICKNESS ADVANTAGES* DISADVANTAGES* COMMENTS 1. Faster to construct than stiffened 1. May experience more vertical 1. Also called a"California Slab". slabs and deeply supported movement than stiffened slabs on 2. Behaves similar to a mat foundation. foundations. deep foundations. 2. Eliminates digging of grade 2. For same amount of concrete, 3. Flat slab rests directly on underlying beams. potentially has more vertical soil. 3. Lack of grade beams makes it differential displacement that may 4. May include a perimeter grade beam easier to jack against if occur except for relatively small and as a root retarder or to prevent underpinning is later required. thick slabs. erosion. 3. Typically uses more concrete and 5. Typically reinforced with steel reinforcement than a stiffened conventional deformed bar reinforcing slab-on-grade(Example: 15"flat or post-tensioned cable. slab is required to provide 6. Suitable for deep sandy soil or equivalent stiffness of a 4"slab foundations having consistent subsoil stiffened with 12"wide x 24"deep formations with low propensity for grade beams spaced on 10'centers. volumetric movement. This dictates 1.9 times more concrete for a flat slab). 4. More easily allows roots to grow below foundation if there are no perimeter grade beams. 5. Subgrade and fill must be compacted if it does not meet minimum density requirements. 6. Does not prevent foundations from tilting. *Compared to other foundation systems as described in Sections 4.1.1 to 4.2.3. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low•Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 19 of 42 4.3 MIXED DEPTH SYSTEMS Mixed depth systems are foundations that extend to different bearing depths. They are sometimes used due to concentrated loads. Although their use is discouraged for certain applications, mixed depth foundation systems are sometimes used. They may be used for new buildings with large plan areas located on a site with widely varying soil conditions, for new buildings on sites with a substantial amount of deep fill, for new buildings on a sloping hillside, for new buildings located next to a waterway or slopes greater than 5%, for existing buildings when adding a new addition, etc. When a new addition is added onto an existing building, consideration must be given to the depth of the new foundation system used for the new addition versus the depth of the existing foundation system used for the original structure. 4.3.1 Mixed Depth System for All-New Building Construction 1 • � /441"1 ; 9\ In situ or otherwise competent soil N�f -----Variable depth foundations Figure 4.3.1 Mixed Depth System for All New Building Construction Because of the increased possibility of differential movement, mixed depth systems are not often used for all-new construction except in areas of sloping grades and sloping strata. TABLE 4.3.1 MIXED DEPTH SYSTEM FOR ALL-NEW BUILDING CONSTRUCTION ADVANTAGES* DISADVANTAGES* COMMENTS 1. More economical than uniformly 1. More likely to experience 1. Pier depth,if included,may vary to deep foundation system. differential movement than follow bearing stratum or to address foundations of uniform depth. slope instability issues. 2. Often used for perimeter and point loaded commercial buildings. *Compared to other foundation systems as described in Sections 4.3.1 to 4.3.3. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 20 of 42 4.3.2 Mixed Depth System for Building Additions with Deep Foundations Slab on compacted structural till or structurally isolated slab Addition Existing structure r- j - ,'rz„1L MK 7111 IIt Structural dowels ”`Deep foundation In situ or otherwise competent soil. Figure 4.3.2 Mixed Depth System for Building Addition with Deep Foundations Sometimes building additions are designed with deeper foundations than the original building in order to reduce movement of the addition. This is because the foundation of the older portion of the building has stabilized. TABLE 4.3.2 MIXED DEPTH SYSTEM FOR BUILDING ADDITIONS WITH DEEP FOUNDATIONS ADVANTAGES* DISADVANTAGES* COMMENTS 1. Addition is more stable than a I. More expensive than using a 1. When used in conjunction with a new new grade-supported foundation shallow foundation system for new structurally isolated slab(i.e.isolated due to less seasonally active soils addition. from soil movement,and structurally at increased foundation depth. connected to existing building) minimizes risk of differential movement. *Compared to other foundation systems as described in Sections 4.3.1 to 4.3.3. 4.3.3 Mixed Depth System for Building Addition with Shallow Foundations Structural dowels Existing structure / Addition ji [ In situ or otherwise 'ompetent soil Slab on compacted SYSTEM NOT RECOMMENDED structural fill or structurally isolated slab Figure 4.3.3 Mixed Depth System for Building Addition with Shallow Foundations FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 21 of 42 Sometimes additions are built with shallower foundations than the original building in order to reduce the cost of construction. TABLE 4.3.3 MIXED DEPTH SYSTEM FOR BUILDING ADDITION WITH SHALLOW FOUNDATIONS ADVANTAGES* DISADVANTAGES* COMMENTS 1. More economical than uniformly I. On expansive,compactable,or 1. Not recommended due to high deep foundation system. compressible soils,more shallowly probability of differential movement. supported addition is likely to move more than existing building. *Compared to other foundation systems as described in Sections 4.3.1 to 4.3.3. 5.0 FOUNDATION COMPONENT DESIGN OPTIONS This section covers the advantages and disadvantages of common component design options for the systems that were discussed in Section 4.0. Components are referenced to other components in the same category. 5.1 DEEP SUPPORT COMPONENTS This section discusses deep foundation support components that are commonly used in new construction for residential and other low-rise buildings. This includes drilled and underreamed piers, drilled straight-shaft concrete piers, auger-cast concrete piles, displacement piles, and helical piers. 5.1.1 Drilled and Underreamed Concrete Piers f Zone cif active Depth of moisture constant suction /Ptt;r Constant 45"minliTlUf l v moisture Simi Figure 5.1.1 Drilled and Underreamed Concrete Piers FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 22 of 42 Drilled and underreamed piers are cast-in-place concrete foundation components with an enlarged bearing area extending downward to a soil stratum capable of supporting the loads. Drilled and underreamed concrete piers have also been referred to as drilled piers, drilled shafts, caissons, drilled caissons, belled caissons, belled piers, bell-bottom piers, foundation piers, bored piles, and or drilled-and-underreamed footings. The depth of the drilled pier should extend to a depth below the moisture active zone that is sufficient to anchor the pier against upward movements of swelling soils in the upper active zone. TABLE 5.1.1 DRILLED AND UNDERREAMED CONCRETE PIERS ADVANTAGES* DISADVANTAGES* COMMENTS 1. Has a long track record, 1. Installation requires a minimum of 1. Many contractors falsely believe approaching a century of use. four different procedures:shaft underreams should be founded at a 2. Provides better lateral load drilling,underreaming,reinforcing certain color or stiffness clay rather resistance than other deep steel placement,and concrete than at depth shown on foundation foundations with smaller placement. engineering drawings. projected surface areas. 2. Requires removing excavated soils 2. Slump should be greater than 5 inches 3. Underreamed portion off-site. to prevent honeycombing. economically provides large end 3. Sloughing of soils at pier shaft and 3. Vertical reinforcement must be used bearing capacity. bell may create problems. to resist tensile forces due to friction 4. Most commonly used deep 4. Difficult to confirm integrity of on shaft from swelling soils. foundation component in Houston concrete placed under groundwater 4. May be constructed in areas with high area. or slurry conditions. groundwater table by using slurry 5. Easier to install than displacement 5. May be difficult for some displacement method. piles in very stiff sandy soils. contractors to install drilled piers 5. Can be installed through sandy layers below a depth of 15 feet because of by using retrievable casing. equipment limitations. 6. Requires waiting until concrete sufficiently cures before applying load. 7. Drilling drilled piers below soil active moisture zone in Houston area often results in encountering water or sands. *Compared to other deep supporting elements as described in Sections 5.1.2 to 5.1.5. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 23 of 42 5.1.2 Drilled Straight-Shaft Concrete Piers t Depth of Zone of active constant moisture suction Pier Con stant �� moisture Zone Figure 5.1.2 Drilled Straight-Shaft Concrete Piers Drilled piers are cast-in-place concrete foundation components extending downward to a soil stratum capable of supporting the loads. Drilled straight-shaft concrete piers are not underreamed. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 24 of 42 TABLE 5.1.2 DRILLED STRAIGHT-SHAFT CONCRETE PIERS ADVANTAGES* DISADVANTAGES* COMMENTS 1. Quality control is simpler than for 1. Soil borings are required to be 1. Many contractors falsely believe drilled and underreamed piers. deeper than underreamed piers, underreams should be founded at a 2. Shafts are efficient at preventing which adds to cost. certain color or stiffness clay rather lateral movement.Shafts are 2. Geotechnical reports do not than at depth shown on foundation typically larger diameter than routinely provide shaft allowable engineering drawings. drilled and underreamed piers, skin friction capacity values. 2. Only recently used as an alternative to and provide better lateral load 3. Usually requires removing drilled and underreamed footings in resistance. excavated soils off-site. light foundation industry. 3. Typically installed deeper than 4. May require steel casing to drill 3. Slump should be greater than 5 inches underreamed piers due to easier through sandy soils. to prevent honeycombing. inspection. 4. Vertical reinforcement must be used 4. Has a long track record,more 5. May require slurry or concrete to be to resist tensile forces due to friction than a century of use. pumped to bottom of hole when on shaft from swelling soils. groundwater is encountered. 5. Easier to install than displacement 6. Requires waiting until concrete piles in very stiff sandy soils. sufficiently cures before applying load. 7. Sloughing of soils may create problems. S. Difficult to confirm integrity of concrete placed under groundwater or slurry conditions. 9. May be difficult for some contractors to install drilled piers below a depth of 15 feet because of equipment limitations. 10.Drilling straight-shaft piers often results in encountering water or sands. *Compared to other deep supporting elements as described in Sections 5.1.1 and 5.1.3 to 5.1.5. 5.1.3 Auger-Cast Concrete Piles Zoe of active _ moisture Depth of constant Constant SUctioI1 moisture Zone Figure 5.1.3 Auger-Cast Concrete Piles FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 25 of 42 Auger cast piles are installed by rotating a continuously-flight hollow shaft auger into the soil to a specified depth. Cement grout is pumped under pressure through the hollow shaft as the auger is slowly withdrawn. TABLE 5.1.3 AUGER-CAST CONCRETE PILES ADVANTAGES* DISADVANTAGES* COMMENTS 1. Drilling through water or sands is 1. Reinforcing cage must be installed 1. Commonly utilized in situations not a problem. after auger is removed,which limits drilling through collapsing soils and 2. Can be installed in low headroom depth of reinforcing cage that can be emerging free water. applications. installed and may result in inadequate concrete cover due to 3. Can be easily installed at angles cage misalignment. other than vertical. 2. If singly reinforced,auger-cast piles do not provide significant bending resistance. 3. Higher mobilization costs than for other systems. 4. Fewer contractors are available that offer this system,making construction pricing less competitive. *Compared to other deep supporting elements as described in Sections 5.1.1,5.1.2,5.1.4 and 5.1.5. 5.1.4 Displacement Piles Zone of active moisture Depth of constant Constant suction moisture zone Displacement piles Figure 5.1.4 Displacement Piles For the purpose of this document, displacement piles are defined as relatively long slender members driven, vibrated, or pressed into the soil while displacing soil at the pile tip. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 26 of 42 TABLE 5.1.4 DISPLACEMENT PILES ADVANTAGES* DISADVANTAGES* COMMENTS 1. No excavated soils to remove. 1. Vibrations and noise that occur 1. Typically used at shoreline locations, during installation can be a problem. swamps,marshes,or other soft soil 2. Only one trade typically involved during installation. 2. Difficult to install through stiff sand areas. 3. Easier to remove than drilled piers strata. if future demolition is required. 3. Because of relatively small 4. Can be installed through soft diameters,grouping or clustering soils and water-bearing strata. may be required,which can lead to other potential problems. *Compared to other deep supporting elements as described in Sections 5.1.1 to 5.1.3,and 5.1.5. 5.1.5 Helical Piers Zone of �al, Depth of CCt1"i constant _ suction moisture t Helix C: ,,,') Constant �.` }TM ' _ j moisture (- Zone _) Figure 5.1.5 Helical Piers Steel helical piers, also known as screw anchors or screw-in piles, have been used since the early 1950s as tie back anchors for retaining walls and as foundations for lighthouses, substations,towers, heavy equipment, and other similar applications.They are now gaining popularity for use in supporting heavier foundations such as residential and other low-rise buildings. The anchor consists of a plate or series of steel plates formed into the shape of a helix to create one pitch of a screw thread.The shape of the plate permits easy installation, which is accomplished by applying torque to the shaft of the anchor and screwing it into the ground using rotary motors. The anchors may be used to resist a tensile or compressive load, which is accomplished by means of bearing pressure resistance on the area of each helix, and not by skin friction along the shaft. The plate helices of helical pier foundations are attached to a central high-strength steel shaft that may be segmented to facilitate construction and to allow various combinations of the number and diameter of helices used. The pier is screwed into the soils until the applied torque readings indicate that the necessary load capacity has been achieved or until the desired depth below the moisture active zone of the expansive soils is obtained. In new construction, the pier shafts are typically anchored to the grade beams by using fabricated brackets that are tied to the grade beam reinforcing before placing the concrete, and bolted to the top of the pier shafts. The bracket consists of a flat horizontal plate FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 27 of 42 welded to a vertical square tube that slips over the shaft of the pier. The plate is embedded into the grade beam concrete. TABLE 5.1.5 HELICAL PIERS ADVANTAGES* DISADVANTAGES* COMMENTS 1. Can be installed in low headroom 1. Fewer contractors are available that 1. Additional protective coatings(e.g., applications in limited access offer this system,and construction coal-tar epoxy)or cathodic protection areas. pricing is less competitive. may be used to control corrosion. 2. Shaft of helical pier has small 2. Usually requires on-site test pier to surface area,which limits amount verify installability and load bearing of uplift or drag-down frictional capacity. forces that may occur due to 3. Although steel is often galvanized, vertical movements of expansive corrosion may limit life expectancy. soils. 3. Only licensed contractors may be 4. In very soft soils with low lateral used to install helical pier restraint,external concrete jacket is foundations,which provides some required to prevent buckling of means of assuring that contractors small shaft under large loads. are tested and trained in all facets 5. Square shafts of helical piers disturb of helical pier construction. soil around shaft during installation 4. Does not require excavation of to some extent,and may result in soil for installation,thus gaps occurring between soil and providing minimal disturbance to shaft along full length of pier.This site. gap may become pathway for water to flow down around shaft and 5. Can be installed in less time than activate swelling of dry expansive drilled piers or augered piles. soils in non-active zone,and may 6. Can easily be installed at a batter also allow air and moisture to speed to resist lateral loads on up rate of steel corrosion. foundation. 6. Vertically installed helical piers 7. Shaft extensions can easily be provide little resistance to lateral added to install load-bearing forces because of their small shaft helices deep below soil moisture diameter. active zone. 8. Loads may be applied immediately after installation. 9. Can be installed in all types of local weather conditions. 10.Only one trade typically involved during installation. *Compared to other deep supporting elements as described in Sections 5.1.1 to 5.1.4. 5.2 SLAB AND GRADE BEAM REINFORCING Since concrete is weak in tension, concrete slabs and grade beams are almost always reinforced with some type of steel reinforcing.The most common design options include post-tensioned reinforcing, deformed bar reinforcing, welded wire fabric reinforcing, and fiber reinforcing. Under special circumstances, unreinforced plain concrete may also be used. Advantages and disadvantages of these types of reinforcement for slab-on-grade and grade beam applications are discussed below. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 28 of 42 5.2.1 Post-Tensioned Reinforcing Post-tensioned concrete is a type of prestressed concrete in which the cables are tensioned after partial curing of the concrete has occurred. Pretensioned prestressed concrete, in which the cables are tensioned before placement of concrete around them, is not commonly used for slabs and grade beams in residential and other low-rise buildings. On the other hand, post- tensioned reinforcing has become the norm for residential slabs in most Texas metropolitan areas. Post-tensioned reinforcing consists of high-strength steel wire strands,typically referred to as tendons or cables,which are encased in plastic sheathing or ducts. When also used near the bottom of grade beams,the tendons are usually located near the top of the grade beam at the ends of the span and draped into the bottom portion of the grade beam near mid-span. Tendons typically consist of 1/2-inch diameter high-strength seven-wire strands having a yield strength of 270 ksi.The tendons are elongated by hydraulic jacks and held in place at the edges of the foundation by wedge-type anchoring devices. The type of tendons typically used in residential slabs and grade beams are single-strand unbonded tendons, in which the prestressing steel is not actually bonded to the concrete that surrounds it except at the anchored ends. This is accomplished by coating the steel strands with corrosion-inhibiting grease and encasing them in extruded plastic protective sheathing that acts as a bond-breaker. The tendons are typically fully stressed and anchored 3 to 10 days after concrete placement. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low•Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 29 of 42 TABLE 5.2.1 POST-TENSIONED REINFORCING ADVANTAGES* DISADVANTAGES* COMMENTS 1. Costs less than conventional steel 1. Requires specialized knowledge and 1. Normally used locally to reinforce rebar reinforcing. expertise to design,fabricate, stiffened slabs-on-grade but may be 2. Speeds up construction because assemble,and install. used for other configurations as well. there are fewer pieces to install 2. Geotechnical design parameters, 2. Post-tensioned foundations are than conventionally reinforced. such as ym and em,are not typically designed using Post 3. Reduces post construction cracks consistently defined among Tensioning Institute(PTI)publication in concrete slabs. geotechnical engineers. Design and Construction of Post- 3. Slab design can be compromised if Tensioned Slabs-on-Ground. 4. Can reduce required amount of cracks open before stressing and fill 3. Compared to other types of post- control joints in slab. with debris. tensioned construction,residential 5. Slab is designed as an uncracked slabs are lightly reinforced with section,therefore should require 4. Post-tension design utilizing deep average concrete compression levels less concrete. beams is less effective than ranging only between 50 psi and 100 deformed bar reinforcing because of greater eccentricity and associated psi. bending moments. 5. Additional operations such as stressing,cutting,and grouting are required after concrete placement. 6. If a tendon or anchorage fails or a blowout occurs,additional operations are required for repair. 7. Tendon end anchorages,which are highly stressed critical elements of system,are located at exterior face of foundation where exposed strand ends and anchors may be susceptible to corrosion. 8. Post-tensioned reinforced foundations are susceptible to potentially dangerous blowouts,in which sudden concrete bursting failure occurs during or after stressing. 9. Making penetrations into slab can be hazardous due to presence of tensioned cables. 10.Cannot prevent cracks prior to stressing caused by plastic shrinkage,plastic settlement,and crazing at slab surface. *Compared to other types of slab and grade beam reinforcing described in Sections 5.2.2 to 5.2.5. 5.2.2 Deformed Bar Reinforcing Deformed bar reinforcing, commonly call rebar,typically consists of ASTM 615 steel having a yield strength of either 40 or 60 ksi. Grade 40 rebar was more common in pre-1970 construction, and Grade 75 rebar is expected to become more common in the future. Deformed bar reinforcing is categorized as"passive"reinforcement since it does not carry any force until the concrete member deflects and cracks under applied loads. On the other hand, post-tensioned tendons are considered"active"reinforcing because they are prestressed and carry tensile force even when loads are not applied to the concrete member. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 30 of 42 TABLE 5.2.2 DEFORMED BAR REINFORCING ADVANTAGES* DISADVANTAGES* COMMENTS 1. Less technical installation 1. Requires specialized knowledge and 1. Some local building officials do not operations than for a post- expertise to design,fabricate, require deformed bar reinforced tensioned foundation system. assemble,and install. foundations to be engineered,even 2. Post-construction slab 2. Costs more than post-tensioned though design has similar difficulty as penetrations are less hazardous to reinforcing. does post-tensioned foundations. install than in slabs with post- 2. Deformed bar reinforced slab reinforcing. 3. Slower to construct than post- tensioned foundations are typically designed per tensioned reinforced slabs American Concrete Institute(ACI) 3. Field splices are easier to 4. Foundation performance is more publication ACI 360R,Design of implement. sensitive to correct placement of Slabs on Grade,charts from Portland slab reinforcement. Cement Association(PCA) publications Concrete Floors on Ground and Slab Thickness Design for Industrial Concrete Floors on Grade,Wire Reinforcement Institute (WRI)publication Design of Slabs on Grade,Building Research Advisory Board(BRAB)publication Criteria for Selection and Design of Residential Slabs-on-Grade,or finite element methodology. 3. Local building officials may not require construction certification by engineers of foundations using only deformed bar reinforcing. *Compared to other types of slab and grade beam reinforcing described in Sections 5.2.1 and 5.2.3 to 5.2.5. 5.2.3 Welded Wire Fabric Reinforcing Welded wire fabric concrete reinforcing consists of cold-drawn wire in orthogonal patterns, square or rectangular,that is welded at all intersections, and is typically used in slab construction. Welded wire fabric(WWF) is commonly called "wire mesh",but mesh is a much broader term that is not limited to concrete reinforcement. Welded wire fabric may be made of smooth wire(ASTM A185) or deformed wire(ASTM A497), and may be manufactured in sheets (usually wire sizes larger than W4)or rolls(usually wire sizes smaller than W1.4). FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low.Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 31 of 42 TABLE 5.2.3 WELDED WIRE FABRIC REINFORCING ADVANTAGES* DISADVANTAGES* COMMENTS 1. Welded wire fabric rolls can be 1. Welded wire fabric is difficult to 1. Welded wire fabric reinforced manufactured in any lengths,up position and hold in place within residential foundations are typically to maximum weight per roll that thickness of slab. designed per Wire Reinforcement is convenient for handling(100- 2. Shipping restrictions as well as Institute(WRI)methodology. 200 ft). pp g manufacturing limitations may limit 2. Local building officials may not 2. Has greater yield strength than maximum sheet size. require engineering certification of conventional deformed bar foundations using only welded wire reinforcing,which can result in 3. Application is generally limited to fabric. reducing required cross-sectional slabs only. area of steel. 4. Heavy welded wire fabric 3. Development lengths are typically reinforcement may not be readily much smaller than for deformed available,and may require special bar reinforcing. order and/or long lead time. 4. Concrete shrinkage cracks can be 5. Slab crack performance is more kept smaller due to confinement sensitive to correct placement of offered by welded cross wires, reinforcement. and microcracking is better 6. Practice of placing wire mesh on distributed. subgrade and using hooks to lift it, 5. Labor costs to install welded wire as workers walk on mesh,invariably fabric are less than to install results in large areas of mesh conventional deformed bar remaining at bottom of slab. reinforcing(through elimination of tying reinforcing rods and faster placement of large sheets). *Compared to other types of slab and grade beam reinforcing described in Sections 5.2.1,5.2.2,5.2.4,and 5.2.5. 5.2.4 Fiber Reinforced Concrete Fiber reinforced concrete consists of synthetic or steel fibers that help to control plastic shrinkage cracking,plastic settlement cracks. Helps reduce bleeding and water migration to slab surface, which helps to control water-cement ratio and produce concrete with less permeability and improved toughness. Fiber reinforced concrete helps increase impact resistance and surface abrasion resistance of concrete. Fiber reinforced concrete is not a substitute for structural reinforcing per ACI 544R-88. Therefore, advantages and disadvantages are not given. 5.2.5 Unreinforced Concrete Unreinforced concrete, also known as "plain" concrete, is concrete without any reinforcing. Soil-supported concrete slabs may be designed as plain concrete, as well as continuously supported grade beams. Unreinforced concrete is not used for structural foundations on expansive soils.Not recommended for use in slabs subject to movement unless cracking is not objectionable. Therefore, advantages and disadvantages are not given. 5.3 VOID SYSTEMS UNDER GRADE BEAMS AND PIER CAPS Voids used by some engineers under grade beams and concrete caps for deep foundations are commonly created by using the same type of wax-impregnated corrugated cardboard forms described in Section 4.1.1.1. If the grade beams are constructed by using the trenching method FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 32 of 42 in which concrete is cast directly against the soil in the excavated trenches, self-disintegrating void forms must be used. An alternate method of grade beam construction is to form the sides of the concrete grade beams, particularly for foundation designs that use non-expansive backfill that elevate the slab above the surrounding grade for drainage purposes. In this case, it is possible to use removable forms to create the voids under the grade beams, and to install strip forms along the bottom edges of the grade beams to keep the soil from filling the voids when backfilling against the sides of the grade beams. 5.4 VAPOR RETARDERS A vapor retarder(sometimes called a vapor barrier) is sheeting material, usually polyethylene film, which is placed under a ground level concrete slab in order to reduce the transmission of water vapor from the soils below the foundation up through the concrete slab. Vapor retarders are commonly used where moisture can migrate from below the slab and cause damage to floor coverings, household goods, or stored materials. Vapor retarders should be overlapped at least 6" at the joints, and should be carefully fitted around pipes and other service penetrations through the slab. In typical southeast Texas area slab-on-grade construction,the vapor retarder is normally placed directly on top of the finish-graded in situ clay or sandy clay soil, or when fill is added, on top of the non-expansive select fill. If cardboard void cartons are used,the vapor retarder should be placed above the void forms in order to allow moisture to degrade the void boxes. For residential construction in areas having expansive soils, concrete is most commonly placed directly on the vapor retarder. At grade beam locations,the vapor retarder is normally draped down into the excavated trench and may be continuous around the exterior surface of the grade beam. 5.5 GRADE-BEAM-TO-PIER CONNECTIONS Traditionally, drilled pier shafts in new construction have been tied to the grade beams with hooked or long straight rebar anchorage to create a connection.The recent trend over the last decade in the Houston area residential construction market is to allow the grade beams to float on top of the deep foundation components with no vertical restraints. This eliminates stresses due to fixed pier-to-beam connections. 5.5.1 Grade-Beam-to-Pier Connections with No Restraints Grade-beam-to-pier connections with no restraints means that the foundation grade beams are cast atop the already cured drilled piers,which are flat and allow the grade beam to translate relative to the pier in all directions except vertical downward. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low•Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 33 of 42 TABLE 5.5.1 GRADE-BEAM-TO-PIER CONNECTIONS WITH No RESTRAINTS ADVANTAGES* DISADVANTAGES* COMMENTS 1. Allows foundation to rise more 1. Foundation may move laterally due uniformly if underlying soils to swelling soils or sloping sites. swell. 2. After concrete is placed,cannot 2. Extended pier steel is not bent easily verify if reinforcing steel was during construction of grade installed in piers. beams 3. Pier steel does not interfere with trencher during grade beam excavation. 4. Easier to clean mud from top of pier caps. *Compared to other types of grade-beam-to-pier connections described in Sections 5.5.1 to 5.5.3. 5.5.2 Grade-Beam-to-Pier Connections with Horizontal-Only Restraints Grade-beam-to-pier connections with horizontal-only restraints means that the foundation grade beams have a positive connection to the piers in any lateral direction,but the grade beams are allowed to translate vertically upward, relative to the piers. TABLE 5.5.2 GRADE-BEAM-TO-PIER CONNECTIONS WITH HORIZONTAL-ONLY RESTRAINTS ADVANTAGES* DISADVANTAGES* COMMENTS 1. Horizontal foundation movement 1. Requires additional labor and 1. Bond-breakers,such as sleeved is limited. material. deform bars,non-deformed bar 2. Allows foundation to rise more dowels,and shear keys may be used. uniformly if underlying soils 2. Used at sloping sites where lateral swell. resistance is required. *Compared to other types of grade-beam-to-pier connections described in Sections 5.5.1 to 5.5.3. 5.5.3 Grade-Beam-to-Pier Connections with Horizontal and Vertical Restraints Grade-beam-to-pier connections with horizontal and vertical restraints means that the foundation grade beams are connected to the top of the piers in such a way that there can be no relative translation in any direction. TABLE 5.5.3 GRADE-BEAM-TO-PIER CONNECTIONS WITH HORIZONTAL AND VERTICAL RESTRAINTS ADVANTAGES* DISADVANTAGES* COMMENTS 1. Can provide uplift resistance from 1. Impedes or prevents jacking of a 1. Connection typically is an extension swelling soils if piers are foundation that must be lifted.Pier of pier shaft vertical deformed adequately anchored. reinforcing must severe before reinforcement. 2. Horizontal foundation movement lifting. 2. Necessary at sloping sites where is limited. 2. Does not allow grade beams to lateral resistance is required. freely lift off piers if upper strata heave occurs.This can cause distress in slab because it is more flexible than grade beams. 3. Beams,beam-to-pier connections, and slab must be designed for uplift forces due to swelling soils. *Compared to other types of grade-beam-to-pier connections described in Sections 5.5.1 to 5.5.3. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 34 of 42 6.0 FOUNDATION SITE DESIGN OPTIONS The various types of mitigation options to limit the damaging effects of soil swelling due to improper drainage and soil shrinkage due to transpiration of trees and shrubbery that are discussed in this guide may be categorized into two basic groups: (1)moisture control systems, and (2)vegetation control systems. 6.1 MOISTURE CONTROL SYSTEMS Moisture control systems mitigate damage by controlling the amount of water and moisture that enter into the site soils.This includes methods to control stormwater runoff and methods of providing irrigation to site vegetation. 6.1.1 Site Drainage Systems Three methods of controlling site drainage include site grading, French drains, and area drains. These systems reduce vertical movements of building foundations by moderating the effects of seasonal moisture changes. 6.1.1.1 Site Grading Site grading causes the excess water to flow away from the foundation via surface sloping and drainage swells. TABLE 6.1.1 SITE GRADING ADVANTAGES* DISADVANTAGES* COMMENTS 1. Fill materials are readily 1. Improper grading may cause water 1. Materials should consist primarily of available. to shed to adjacent properties. clay.Do not use bank sand or clayey 2. Less maintenance required 2. Fill materials require proper sand or silts. afterwards. compaction and material. 3. Inadequate drainage is easier to detect. 4. Most economical. *Compared to other types of site drainage systems described in Sections 6.1.1. 6.1.1.2 French Drains French drains are subsurface drainage systems that are used around the perimeter of a foundation to remove free water in the subsoil. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 35 of 42 TABLE 6.1.1.2 SUBSURFACE DRAINAGE SYSTEMS(FRENCH DRAINS) ADVANTAGES* DISADVANTAGES* COMMENTS 1. Helps reduce moisture infiltration 1. Not very effective in expansive clay 1. Normally used only when site is too from underground water sources. soils because soil suction is high flat to accommodate proper grade 2. Suitable when site grading is not when soil permeability is very low. slopes. an available option. 2. Can cause erosion of surrounding 2. Usually consists of a 4"or larger PVC soil,causing settlement of perforated pipe,covered with sand foundation if too close. and gravel and sloped to a positive 3.Requires some maintenance but is outlet. difficult to monitor. 3. Also utilized in removing moisture 4. French drain fabric membranes may behind retaining and basement walls. tear or be punctured. 5. If clogged,allows water to collect adjacent to foundation and may cause soil heaving. 6. If used in conjunction with a vertical moisture retarder on one side, sufficient geotechnical or geophysical testing is required to determine natural flow direction and source of groundwater. 7. Most expensive system. *Compared to other types of drainage systems described in Sections 6.1.1. 6.1.1.3 Area Drains Area drains(catch basins) are surface collection systems used around the perimeter of a foundation to remove surface water by gravity flow or mechanical lifting. . TABLE 6.1.1.3 AREA DRAINS ADVANTAGES* DISADVANTAGES* COMMENTS 1. Sumps can be utilized to 1. A clogged drain may cause localized 1. Commonly used in back yards when discharge water in low areas flooding. site is too flat to accommodate proper 2. Suitable when site grading is not 2. If used in conjunction with a vertical grade slopes. an available option. moisture retarder on one side, 2. Usually consists of a 4"or larger PVC 3. Water from downspouts can be sufficient geotechnical or non-perforated pipe. geophysical testing is required to discharged into area drainage determine to natural flow direction 3. When used sump failure may cause system. and source of surface water. flooding and may require periodic maintenance. 3. A leaking pipe may cause soils to 4. May be used in conjunction with site erode or swell. grading. *Compared to other types of drainage systems described in Sections 6.1.1. 6.1.2 Moisture Retarder Systems Moisture retarder systems are used to reduce moisture transfer to the soils underneath foundations. Such systems include horizontal moisture retarders and vertical moisture retarders. These systems help moderate effects of seasonal changes on foundation movements. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 36 of 42 6.1.2.1 Horizontal Moisture Retarders Horizontal moisture retarders usually consist of materials of low permeability. These systems extend outward around the edges of the foundation. Sidewalks, driveways, or parking lots may be multifunctional, also serving as moisture retarders. TABLE 6.1.2.1 HORIZONTAL MOISTURE RETARDERS ADVANTAGES* DISADVANTAGES* COMMENTS 1. Readily inspected and maintained 1. Requires larger area to be effective. 1. Usually concrete or asphalt pavement. 2. Requires less slope than green 2. Heaving of retarder may occur due 2. Horizontal moisture retarders slow space(e.g.,only 1/8"/ft.)to to soil hydration. root growth by reducing oxygen achieve positive drainage away transmission to roots. 3. Fabric membrane retarders more from foundation. prone to tear or puncture. 3. Doubles as root retarder. 3. Can double as pavement for 4. Unsecured rigid retarders may parking or sidewalk. "walk-away"from building and allow water infiltration through gap created at edge of building if seal is not maintained. 5. Owner or future owner may remove it,not realizing it serves a design purpose,and inadvertently eliminate benefit it provides. 6. Only retards surface moisture. 7. May not be aesthetically acceptable. *Compared to other types of moisture retarder systems described in Sections 6.1.2. 6.1.2.2 Vertical Moisture Retarders Vertical moisture retarders usually consist of materials of low permeability that extend downward from grade level around the perimeter of the foundation. TABLE 6.1.2.2 VERTICAL MOISTURE RETARDERS ADVANTAGES* DISADVANTAGES* COMMENTS 1. More effective in retarding lateral 1. Higher cost. 1. Usually consists of concrete,steel, moisture migration. 2. Requires severing tree roots and polyethylene or fabric sheets,or 2. Controls vertical movements may compromise tree health. bentonite clay. better. 3. Is difficult to inspect and to know 3. Also functions as a root retarder. when to repair or replace. 4. Fabric membrane retarders more prone to tear or puncture. 5. May retain moisture from under slab leaks and exacerbate heaving. *Compared to other types of moisture retarder systems described in Sections 6.1.2. 6.1.3 Watering Systems Watering systems are usually used to induce moisture into the soils and to water vegetation around the foundation,thereby attempting to provide a constant and uniform moisture condition. During droughts, water may be rationed, preventing use of these systems.A soil moisture sensor with automatic controls is recommended with these watering systems. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 37 of 42 6.1.3.1 Sprinkler Systems An irrigation system consists of below grade piping and above grade sprinkler heads. TABLE 6.1.3.1 SPRINKLER SYSTEMS ADVANTAGES* DISADVANTAGES* COMMENTS 1. May attract tree roots away from 1. If not properly monitored,may 1. Only enough irrigation should be foundations if system is properly result in excess watering,resulting applied to sustain vegetation,so that drained,zoned,and set. in heave or loss of soil bearing. there is no ponding or algae buildup. 2. Provides moisture during dry 2. Leaks may not be detected thereby periods,thereby reducing causing localized foundation movement due to soil shrinkage. movement. 3. Can provide more uniform 3. Requires more maintenance than moisture content to site. other watering systems. 4. Overspray onto superstructures may occur. 5. Results in more waste of water by runoff and evaporation. *Compared to other types of watering systems described in Sections 6.1.3. 6.1.3.2 Soaker Hose Systems Soaker hoses are permeable water conduits resembling garden hoses normally used to water localized areas. TABLE 6.1.3.2 SOAKER HOSE SYSTEMS ADVANTAGES* DISADVANTAGES* COMMENTS 1. Properly maintained soaker hoses 1. Hoses may be subject to premature 1. Normally limited to garden and apply water more slowly to soil deterioration. foundation applications. than sprinkler systems. 2. Sensitive to damage from freezing. 2. Can be buried to reduce evaporation 2. May be used to provide moisture 3. May attract roots toward foundation and avoid damage from lawn to vegetation. if used around perimeter of equipment. 3. Easiest to install. foundation. 4. Hoses may not disburse water uniformly in long runs. *Compared to other types of watering systems described in Sections 6.1.3. 6.1.3.3 Under-Slab Watering Systems Under-slab watering systems are installed under slabs to provide moisture directly below the foundation. These systems typically consist of a network of piping, wells, and moisture sensors, which are intended to function together to maintain a uniform level of moisture in the soil beneath the structure. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 38 of 42 TABLE 6.1.3.3 UNDER-SLAB WATERING SYSTEMS ADVANTAGES* DISADVANTAGES* COMMENTS 1. Low to medium cost although 1. Requires strict monitoring and 1. Low cost foundation watering systems high-cost systems are also maintenance. that do not include a continual soil available. 2. May take a long time to stabilize moisture content monitoring system 2. Minimizes evaporation. vertical building movements. that is connected to moisture release valves is considered an unacceptable 3. Difficult to install underneath system. existing buildings.High-cost system requires cutting holes through slab- at-grade to install system. 4. Soil irregularities and discontinuities may limit effectiveness of system. 5. Dramatic subsidence could occur if system is disabled. 6. Attracts roots toward foundation, which may increase dependency on this system. 7. Monitoring program should be included that entails regular geotechnical testing and foundation level distortion surveys. 8. During droughts,water may be rationed,preventing its use. 9. Moisture sensors are subject to frequent replacement and performance may be unreliable. 10.Desired moisture content under slab is difficult to determine. *Compared to other types of watering systems described in Sections 6.1.3. 6.1.3.4 Drip Watering Systems Drip irrigation slowly applies water to soil under low pressure through emitters, bubblers, or spray heads placed at each plant. TABLE 6.1.3.4 DRIP WATERING SYSTEMS ADVANTAGES* DISADVANTAGES* COMMENTS 1. Offers increased watering 1. Requires strict monitoring and 1. Drip irrigation slowly applies water to efficiency and plant performance maintenance. soil under low pressure through when compared to sprinkler 2. Not permanent. emitters,bubblers,or spray heads irrigation. placed at each plant. 2. Can be installed without 3. Frost sensitive. 2. Normally limited to garden and excavation. 4. May attract roots toward foundation foundation applications. if irrigation is excessive near 3. A moisture meter is recommended building. with this type of system. 5. System may not disburse water uniformly. *Compared to other types of watering systems described in Sections 6.1.3. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 39 of 42 6.2 VEGETATION CONTROL SYSTEMS Vegetation control systems mitigate damage by providing some control over the growth of roots that may penetrate into unwanted areas and cause shrinkage of foundation soils by means of water withdrawal through the transpiration process. 6.2.1 Root Retarder Systems Root retarder systems are typically physical or chemically induced barriers that limit the growth direction of the roots of trees, shrubbery, and other large plants. 6.2.1.1 Vertical Root Retarders Vertical root retarders are vertical barriers that are installed in the ground adjacent to the perimeter of a foundation or around a tree or other large plant. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 40 of 42 TABLE 6.2.1.1 VERTICAL ROOT RETARDERS ADVANTAGES* DISADVANTAGES* COMMENTS 1. Minimal disturbance of 1. Requires severing tree roots, 1. May be an impervious type(e.g., landscaping. necessitating tree pruning or other plastic,concrete or sheet metal piling) 2. Impervious type root retarder also treatment when using near existing or a biocide type. doubles as moisture retarder, trees. 2. Vertical root retarders slow root which can prevent excess 2. May compromise tree health. growth below a foundation by forcing moisture resulting from drainage 3. May compromise tree stability. roots to grow to a greater depth. problems from reaching 3. Should be professional installed to foundation. 4. Will only help to control vertical minimize root damage. foundation movements,not stop it. 5. Limited warranty and limited period 4. Non-impermeable retarders require of effectiveness(for biocide more maintenance. systems). 6. Requires special details for penetration of building utility lines. 7. Very difficult to inspect and to know when to repair or replace. 8. Sometimes difficult or impractical to install below deepest lateral tree roots. 9. Usually aesthetically required to be installed completely below grade, which may allow roots to grow over retarder. 10.Impervious type of root retarder also acts as a moisture retarder,which may interrupt existing natural below-grade moisture movement due to soil suction or gradients. 11.Extensive geotechnical and geophysical testing may be required to ensure that installation of impervious retarders is not detrimental to foundation. 12.For cases where retarder is installed adjacent to structure,foundation support may be compromised in order to install retarder deep enough to be useful. *Compared to other types of vegetation control systems described in Sections 6.2.1. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 41 of 42 6.2.1.2 Horizontal Root Retarders Horizontal root retarders are horizontal barriers that are installed on top of the ground adjacent to the perimeter of a foundation or around a tree or other large plant. TABLE 6.2.1.2 HORIZONTAL ROOT RETARDERS ADVANTAGES* DISADVANTAGES* COMMENTS 1. Doubles as pavement for parking 1. Not as architecturally pleasing, 1. Normally concrete pavement. or sidewalks. especially for residences. Horizontal root retarders slow root 2. Its presence prevents planting of 2. Needs steel reinforcement and growth by minimizing oxygen flow to trees near foundation. expansion joints to prevent cracking roots. 3. Doubles as a horizontal moisture due to ground movement. 2. May not be effective in preventing retarder. 3. Expansion joints and cracks must be root growth. 4. Quick to install. sealed to retard oxygen transfer to soil. 5. Relative low cost. 4. Joint seals require maintenance, which is easily forgotten by Owner. 5. Owner or future owner may remove it,not realizing it serves a design purpose. 6. Tree roots may lift and break retarder causing vertical offsets. *Compared to other types of vegetation control systems described in Sections 6.2.1. 6.2.2 Root Watering Wells Root watering wells are installed near trees to provide moisture below grade. These systems typically consist of a drilled hole filled with coarse material. Piping may be inserted in the holes in order to maintain a clear path for water access. TABLE 6.2.2 ROOT WATERING WELLS ADVANTAGES* DISADVANTAGES* COMMENTS 1. Minimal excavated material. 1. Effectiveness of reducing moisture 1. If used,root watering wells should be 2. Minimal disturbance of withdrawal from under building is installed on side of tree opposite landscaping. questionable. foundation. 3. Can be beneficial to health of 2. Beneficial effects may take long trees by helping them establish time to materialize. roots at a greater depth. 3. Require maintenance. 4. May help keep new tree roots 4. Require ongoing operating costs and from growing under buildings water usage. provided wells are installed away 5. May hit utility line or tree root when from foundation. drilling. 5. Less likely to damage existing 6. Movement of water through tree roots during installation unfractured clays is extremely slow. process. 7. Chlorinated water directly applied to deep roots may be detrimental to tree health. *Compared to other types of vegetation control systems described in Sections 6.2.1. FPA-SC-01-X(DRAFT) Foundation Design Options for Residential and Other Low-Rise Buildings on Expansive Soils 1 April 2004 Issued for Comments Foundation Performance Association-Structural Committee Page 42 of 42 6.3 TREE AND PLANT SELECTION When doing the initial site landscaping design,the proper selection of site vegetation with regard to tree and plant moisture requirements can directly affect future foundation performance. Vegetation selection may also be a deciding factor in the selection of other moisture and vegetation control system design options. TABLE 6.3 TREE AND PLANT SELECTION ADVANTAGES* DISADVANTAGES* COMMENTS 1. Proper tree and plant selection I. Limits available vegetation for 1. An example of site vegetation control may also be aesthetically landscaping design. is Xeriscape landscaping,defined as pleasing. quality landscaping that conserves 2. Owner or future owner may remove water and protects environment,by 2. Proper tree and plant selection trees and shrubbery with low-water- using plants and trees with low-water may increase property value. requirements,not realizing they serve a design purpose. requirements. 2. Selecting plants and trees with low- water requirements can reduce potential for problems caused by vegetation water demands. 3. Using vegetation with low water requirements means less run-off of irrigation water that may carry polluting fertilizers and pesticides to nearby streams or lakes,and less permeation of irrigation water into ground that may leach nutrients deep into soil away from vegetation and increase chances of polluting groundwater. *Compared to other types of vegetation control systems described in Sections 6.2.