HomeMy WebLinkAbout04012004 BSC Agenda Item 5 S •
Attached is the promised re-draft of the foundation amendments. Also attached is an
alternate version with an exception for old-stock housing, drafted along the lines
discussed in development staff meeting yesterday ("old stock" would have to be at least
years old and have no more than % framed area).
Regardless of which version is used, it would be a good idea to clarify if the new
amendments are intended to apply to: (i) one-story garages or accessory buildings, (ii)
semi-enclosed garages or carports, (iii) additions to existing buildings, (iv) similar
structures. The cost impact on these types of structures could be severe.
Also, as we discussed with the BSC, please make sure there is solid engineering
evidence in the file to support each amendment (Example: Evidence that the three
named types of foundations actually perform better in the West University Place area
than the un-named types.)
If these drafts look OK, please circulate them to BSC members, and please let me know
if I am needed to attend the meeting.
/s/ Jim
James L. Dougherty, Jr.
Attorney at Law
5120 Bayard
Houston, Texas 77006
Phone: 713-880-3800
Fax: 713-880-1417
E-Mail: jim(c�jdlaw.prserv.net
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1
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. e. : - •• .. •• _ :. :; • • • '_
professional engineer("RPE"), and the work shall bc:
]a- .- • -; -; -- . - - . • - -„ ; .- - ; :. - _ : . : • : • • I. ,
•; : • • • I• • - • _ •j : • : •. ; • - • • - - - •
less than 450 sq. ft. of gross floor area); and .
fttrthir.
All foundations and structural framing for new buildings with a gross floor area 400
square feet or more must meet the following criteria:
a. They must be constructed in accordance with complete plans and specifications
prepared, signed and sealed by a licensed professional engineer("LPE"). 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. The plans and specifications for each foundation must be based on a written soils
report meeting criteria as to authorship, scope,content and form specified by the
building official. The building official may adopt criteria published by the
Structural Committee of the Foundation Performance Association,Houston,
Texas.
c. Foundations must be one of the following types: (i)pier and beam, (ii) voided
slab, or(iii) slab atop a building pad of compacted select fill extending at least 48
inches below grade level (Exception: Where the soils report indicates a plasticity
index less than 20, no select fill is required.) The BSC may issue a special
exception for another type of foundation, but only upon a showing of engineering
data and opinion to demonstrate that the other type will be as stable, strong and
enduring as the specified types.
d. Each foundation and all structural framing must be professionally observed and
must be certified by an LPE before work proceeds further.
(1) Observations must: (i) be performed either by the certifying LPE or by a
11110 1110.-
person under that LPE's direct supervision and control whose professional
qualifications are approved by the LPE, (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.
(2) Certifications must: (1)refer to and be based upon the professional
observations required by this section, (2) 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 LPE and reported to the building
official and comply with applicable regulations), (3) state that the work
complies with sound engineering practices, (4) comply with criteria as to
form and content as may be specified by the building official, and(5) be
signed and sealed by the certifying LPE.
Exce s tion: The .recedin• criteria do not al el to a foundation for a new buildin• or
buildin• addition on a buildin• site where: i there is an existin•_.rinci.al buildin• at
least .art of which is at least ears old and ii after com.letion of the new
buildin•s and additions, the total framed area of all buildings on the site will not exceed
% of the area of the building site.
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
•
1
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
i !
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 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.
I
fib
J
4
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.
j 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.
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. is :: : - : - .. ..' i• _- . • :. •; : . • .- :- -: , _ - - -;
prafes-siorrafungincer ("RPE"), and thk.,week-shall be.
it based on a soils report from a recognized and reputable firm or agency
NI•
further.
All foundations and structural framing for new buildings with a gross floor area 400
square feet or more must meet the following criteria:
a. They must be constructed in accordance with complete plans and specifications
prepared, signed and sealed by a licensed professional engineer("LPE"). 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. The plans and specifications for each foundation must be based on a written soils
report meeting criteria as to authorship, scope, content and form specified by the
building official. The building official may adopt criteria published by the
Structural Committee of the Foundation Performance Association, Houston,
Texas.
Foundations must be one of the following types: (i)pier and beam, (ii) voided
slab, or(iii) slab atop a building pad of compacted select fill extending at least 48
inches below grade level (Exception: Where the soils report indicates a plasticity
index less than 20, no select fill is required.) The BSC may issue a special
exception for another type of foundation, but only upon a showing of engineering
data and opinion to demonstrate that the other type will be as stable, strong and
enduring as the specified types.
U. Each foundation and all structural framing must be professionally observed and
must be certified by an LPE before work proceeds further.
(1) Observations must: (i) be performed either by the certifying LPE or by a
0
person under that LPE's direct supervision and control whose professional
qualifications are approved by the LPE, (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.
(2) Certifications must: (1)refer to and be based upon the professional
observations required by this section, (2) 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 LPE and reported to the building
official and comply with applicable regulations), (3) state that the work
complies with sound engineering practices, (4) comply with criteria as to
form and content as may be specified by the building official, and (5)be
signed and sealed by the certifying LPE.
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
• 41111iN
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 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).
41,
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.
• •
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April 1 Ct 2004
1
1
Foundations
1 Agenda Item # 5
• •
Geotechnical Engineering Analyses and Report
Minimum Field Investigation
a. Single lots shall have minimum of 2 borings
b. Depth of boring— 15 to 20 feet
II. Minimum Lab Testing
a. Dry Density
b. Moisture Content
c. Atterberg Limits
d. Pocket Penetrometer Estimates of Cohesive Strength
e. Torvane
f. Strength Tests
g. Swell and/or Shrinkage Test
h. Hydrometer Testing
i. Sieve Size %
j. Soil Suction
k. Consolidation
III. GeoTech Report
a. Report Contents
i. Purpose and scope, authorization and limitations of services
ii. Project description, including design assumptions
iii. Investigative procedures
iv. Lab testing procedures
v. Lab testing results
vi. Boring logs and plans showing boring locations
vii. Site characterization
viii. Foundation design info and recommendations
ix. Professional Engineers Seal
• •
4.6.5.2.1
FINAL DRAFT DOCUMENT
(Developed at the 27-July-02 Meeting held in Houston,Texas)
American Society of Civil Engineers
Texas Section
Recommended Practice for the
Design of Residential Foundations
• •
Table of Contents
Section 1. Introduction 1
Section 2. Definition of"Engineered Foundation" 2
Section 3. Design Professionals'Roles and Responsibilities 3
3.1 Geotechnical Services 3
3.2 Design Services 3
3.3 Construction Phase Services 3
Section 4. Geotechnical Investigation 4
4.1 Minimum Field Investigation Program 4
4.2 Minimum Laboratory Testing Program 4
4.3 Geotechnical Report 5
Section 5. Design of Foundations 8
5.1 Design Information 8
5.2 Design Procedures for Slab on Ground 8
5.3 Design Procedures for Structurally Suspended Foundations 9
5.4 Design Procedures for Footing Supported Foundations 10
5.5 Minimum Plan and Specification Information 10
Section 6. Construction Phase Observation 11
6.1 Responsibility for Observations 11
6.2 Minimum Program of Observation and Testing 11
6.3 Compliance Letter 1 1
APPENDIX A 12
APPENDIX B 13
Section B.1 FILL 13
B.1.1 Engineered Fill 13
B.1.2 Forming Fill 13
B.1.3 Uncontrolled Fill 13
Section B.2 Building on Non-Engineered (Forming Or Uncontrolled)Fill 14
a • •
Section 1. Introduction
1.1 Objective
The function of a residential foundation is to support the structure. The majority of foundations
constructed in Texas consist of shallow, stiffened and reinforced slab-on-ground foundations. Many are
placed on expansive clays and/or fills. Foundations placed on expansive clays and/or fills have an
increased potential for movement and resulting distress.
National building codes have general guidelines which may not be sufficient for the soil conditions and
construction methods in the State of Texas. The purpose of this document is to present recommended
practice for the design of residential foundations to augment current building codes to help reduce
foundation related problems. Where the recommendations in this document vary from published
methods or codes, the differences represent the experience and judgment of the majority of the
committee members.
On sites having expansive clay, fill, and/or other adverse conditions, residential foundations shall be
designed by licensed engineers utilizing the provisions of this document. Expansive clay is defined as
soil having a weighted plasticity index greater than 15 as defined by Building Research Advisory Board
(BRAB) or a maximum potential volume change greater than 1 percent. This provision should also
apply where local geology or experience indicates that active clay soils may be present. We propose that
local and state governing bodies adopt this recommended practice.
1.2 Limitation
This recommended practice has been developed by experienced professional engineers and relate
practices they commonly employ to help deal effectively with soil conditions that historically have
created problems for residential foundations in Texas. This recommended practice presumes the
existence of certain standard conditions when, in fact, the combination of variables associated with any
given project always is unique. Experienced engineering judgment is required to develop and implement
a scope of service best suited to the variables involved. For that reason,the developers of this document
have made an effort to make the document flexible. Thus, successful application of this document
requires experienced engineering judgment; merely following the guidelines may not achieve a
satisfactory result. Unless adherence to this document is made mandatory through force of law or by
contractual reference, adherence to it shall be deemed voluntary. This document does not, of itself,
comprise the standard of care which engineers are required to uphold.
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Section 2. Definition of"Engineered Foundation"
An engineered foundation is defined as one for which design is based on three phases:
a. geotechnical engineering information
b. the design of the foundation is performed by a licensed engineer
c. construction is observed with written documentation
These phases are described herein.
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Section 3. Design Professionals' Roles and Responsibilities
3.1 Geotechnical Services
Prior to foundation design, a geotechnical investigation and report shall be completed by a
geotechnical engineer.
3.2 Design Services
The foundation design engineer shall prepare the plans and specifications for the foundation, and
shall be the engineer of record. The foundation shall be built in accordance with the design. The
engineer of record shall approve any design modifications. The geotechnical and foundation
design engineering may be performed by the same individual.
3.3 Construction Phase Services
The engineer of record shall specify on the plans that construction phase observations shall be
incorporated into the foundation construction. These activities shall be performed by: the engineer
of record or a qualified delegate. The qualified delegate may be a staff member under his/her
direct supervision, or outside agent approved by the engineer of record. The observation reports
shall be provided to the engineer of record. The engineer of record shall issue a compliance letter
as described in Section 6.3.
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Section 4. Geotechnical Investigation
4.1 Minimum Field Investigation Program
The geotechnical engineer, in consultation with the engineer of record, if available, shall lay out the
proposed exploration program. . A minimum exploration program for subdivisions shall cover the
geographic and topographic limits of the subdivision, and shall examine believed differences in
geology in sufficient detail to provide information and guidance for secondary investigations, if
any. The geotechnical exploration program should take into account site conditions, such as
vegetation, depth of fill, drainage, seepage areas, slopes, fence lines, old roads or trails, man-made
constructions, the time of year regarding seasonal weather cycles and other conditions that may
affect foundation performance.
As a minimum for unknown but believed to be uniform subsurface conditions, borings shall be
placed at maximum 300 foot centers across a subdivision. Non-uniform subsurface conditions
may require additional borings. A single lot investigated in isolation shall have a minimum of two
borings. Borings shall be a minimum of 20 feet in depth unless confirmed rock strata is
encountered at a lesser depth. However, if the upper 10 ft of soils are found to be predominately
cohesionless, then the boring depth may be reduced to 15 ft.. Borings shall extend through any
known fill or potentially compressible materials even if greater depths are required.
All borings shall be sampled at a minimum interval of one per two feet of boring in the upper 10
feet and at 5-foot intervals below that. In clayey soil conditions, relatively undisturbed tube
samples should be obtained. In granular soils, samples using Standard Penetration Tests should be
obtained. Borings shall be sampled and logged in the field by a geotechnically trained individual
and all borings shall be sampled such that a geotechnical engineer may examine and confirm the
driller's logs in the laboratory.
Exploration may either be by drill rig or by test pit provided the depth requirements are satisfied.
Sites, which are obviously rock with outcrops showing or easily discoverable by shallow test pits,
may be investigated and reported without resorting to drilled borings.
Field logs shall note inclusions, such as roots, organics, fill, calcareous nodules, gravel and man-
made materials. If encountered, the depth to water shall be logged. If the geology or site
conditions indicate, overnight water levels shall be recorded prior to backfilling boreholes.
Additional measurements shall be taken at the direction of the geotechnical engineer.
4.2 Minimum Laboratory Testing Program
The geotechnical engineer, in consultation with the engineer of record, if available, shall develop
the laboratory testing program. Sufficient laboratory testing shall be performed to identify
significant strata and soil properties found in the borings across the site. Such tests may include:
a. Dry Density
b. Moisture Content
c. Atterberg Limits
d. Pocket Penetrometer Estimates of Cohesive Strength
e. Torvane
f. Strength tests
g. Swell and/or Shrinkage Tests
h. Hydrometer Testing
i. Sieve Size Percentage
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j. Soil Suction
k. Consolidation
All laboratory testing shall be performed in general accordance with the American Society for
Testing and Materials(ASTM) or other recognized standards.
4.3 Geotechnical Report
4.3.1 Report Contents
Geotechnical reports shall contain, as a minimum:
a. purpose and scope, authorization and limitations of services
b. project description, including design assumptions
c. investigative procedures
d. laboratory testing procedures
e. laboratory testing results
f. logs of borings and plan(s) showing boring locations
g. site characterization
h. foundation design information and recommendations
i. Professional Engineer's seal
4.3.2 Site Characterization
The geotechnical engineer shall characterize the site for design purposes. The report shall
comment on site conditions which may affect the foundation design, such as:
a. topography including drainage features and slopes
b. trees and other vegetation
c. seeps
d. stock tanks
e. fence lines or other linear features
f. geologic conditions
g. surface faults, if applicable
h. subsurface water conditions
i. areas of fill detected at the time of the investigation
j. other man made features
4.3.3 Foundation Design Information and Recommendations
Reports shall contain the applicable design information and recommendations requested by
the engineer of record for each lot in the project. If the engineer of record is not known at
the time of the geotechnical report, the following design information should be presented, if
applicable:
4.3.3.1 Soil movement potential as determined by the estimated depth of the active zone
in combination with at least two of the following methods (identify each method
used):
a. Potential Vertical Rise as determined by the Texas Department of
Transportation Method 124-E, dry conditions
b. Swell tests
c. Suction and hydrometer tests
d. Linear Shrinkage tests
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e. Any other method which can be documented and defended as good
engineering practice in accordance with the principles of unsaturated soil
mechanics
4.3.3.2 BRAB design information including:
a. Climatic Rating(CW) of the site
b. Weighted Plasticity Index
c. Bearing capacity of the soil
4.3.3.3 Post-Tensioning Institute (PTI) parameters (using their most current design
manual and technical notes) including:
a. em and ym for edge lift and center lift modes (The em and ym in the PTI design
manual are based on average climate controlled soil movements and the
design recommendations should take into account the added effect of trees and
other environmental effects, as noted in the PTI design manual.); and
b. Bearing capacity of the soil.
c. If suction values are used to determine the depth and value of suction
equilibrium or evaluate special conditions such as trees, the values shall be
determined using laboratory suction tests. ym determination shall be based on
suction profile change and laboratory determined values of suction-
compression index.
d. em and ym shall be reported for design conditions for suction profile varying
from equilibrium, and for probable extreme suction conditions.
4.3.3.4 Wire Reinforcing Institute (WRI) parameters including:
a. Climatic Rating(CW) of the site
b. Weighted Plasticity Index
c. Slope Correction Coefficient(Cs)
d. Consolidation Correction Coefficient(C0)
4.3.3.5 Deep Foundation(pier/pile) design information including:
a. Bearing capacity and skin friction along the pier length
b. Pier types and depths, and bearing strata
c. Uplift pressures on the pier and estimated depth of active zone (pier depth
must be below the active zone and provide proper anchorage to resist the
uplift pressures)
d. Down drag effects on the piers
4.3.3.6 Shallow foundations (including post and beam footings) design parameters.
a. Bearing capacity and footing depth
b. Minimum bearing dimension
4.3.3.7 Soil treatment method(s) to reduce the soil movement potential and the
corresponding reduction in predicted movement.
4.3.3.8 Lateral pressures on any retaining structures or on piers undergoing lateral forces.
4.3.3.9 Trees and other site environment concerns that may affect the foundation design.
Information useful for design and construction of residential foundations is
presented in Appendix A.
4.3.3.10 Moisture control procedures to help reduce soil movement.
4.3.3.11 Surface drainage recommendations to help reduce soil movement.
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4.3.3.12 Potential for load induced settlement.
4.3.3.13 On sloping sites, recommend whether a slope stability analysis is required due to
possible downhill creep or other instability that may be present.
4.3.3.14 The presence and methods of dealing with existing and proposed fill. Fill criteria
useful for design and construction of residential foundations is presented in
Appendix B.
4.3.3.15 Geotechnical considerations related to construction.
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Section 5. Design of Foundations
5.1 Design Information
The foundation design engineer shall obtain sufficient information for the design of the foundation.
This may include:
a. information gathered by a site visit
b. the subdivision plan, site plan or plat
c. the topography of the area including original and proposed final grades
d. the geotechnical report
e. special requirements of the project
f. the project budget
g. the architectural elevations and floor plans and sufficient additional architectural information to
determine the magnitude, construction materials and location of structural loads on the
foundation
h. exposed or architectural concrete schedule, if applicable
5.2 Design Procedures for Slab on Ground
5.2.1 The foundation engineer shall utilize one of the following methods, with the modifications
presented in this section, as a minimum:
a. BRAB
b. Finite Element
c. PTI
d. WRI
e. other methods which can be documented and defended as good engineering practice
5.2.2 Input variables for residential slab-on-ground foundations shall be as follows:
5.2.2.1 BRAB:
a. Use the current design manual and technical notes, and the following design
provisions.
b. Regardless of the actual beam length, the analysis length should be limited to
a maximum of 50 ft; and
c. Use a maximum long term creep factor as provided in ACI 318, Section
9.5.2.5.
5.2.2.2 Finite Element:
a. Use soil support parameters that can be documented and defended as good
engineering practice in accordance with the principles of unsaturated soil
mechanics;
b. Use a cracked moment of inertia for beams that exceed the cracking moment;
and
c. Use a maximum design deflection ratio of 1 / 360 (deflection ratio is defined
as the maximum deviation from a straight line between two points divided by
the distance between the two points).
5.2.2.3 PTI:
a. Use the current design manual and technical notes, and the following design
provisions.
b. Provide minimum residual average prestress of 100 psi.
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c. Maintain the calculated prestress eccentricity within 5.0 inches. Bottom beam
reinforcing should always be used.
d. If the computed concrete tensile stress at service loads, after accounting for
prestress losses, exceeds 4If c, provide bonded additional reinforcement at the
top or bottom of the beam as required by tensile forces equal to 0.0033 times
the gross beam section. The transformed area of steel may be used to
determine a new stiffness value for the beam.
e. The em and ym in the PTI design manual are based on average climate
controlled soil movements and the design analysis should take into account
the added effect of trees and other environmental effects, as noted in the PTI
design manual.
5.2.2.4 WRI:
a. Use the current design manual and technical notes, and the following design
provisions.
b. Regardless of the actual beam length, the analysis length should be limited to
a maximum of 50 ft; and
c. The minimum design length (Lc) shall be increased by a factor of 1.5 with a
minimum increased length of 6 ft.
5.2.3 Design Considerations
The foundation design engineer should consider the following (deviation shall be based on
generally accepted engineering practice):
5.2.3.1 The latest ACI publications.
5.2.3.2 Exterior corners may require special stiffening. This can be accomplished with
diagonal beams or parallel interior beams near the perimeter beams.
5.2.3.3 Provide continuous beams at reentrant corners. For post tensioned foundations, all
exterior and interior beams should be continuous. For conventionally reinforced
beams, interior beams may be discontinous as long as the beam is continued a
distance equal to at least twice the Lc distance.
5.2.3.4 Provide stiffening beams perpendicular to offsets (such as fireplaces or bay
windows) in perimeter beams when the offset exceeds 18-inches.
5.2.3.5 Provide interior beams at concentrated loads such as fireplaces, columns and
heavy interior line loads.
5.2.3.6 Sites with soil movement potential (see Section 4.3.3.1) exceeding 1.0 inch
should have special design considerations such as strengthened sections, revised
footprint, site soil treatment, or structurally suspended foundation if any of the
following conditions is present:
a. a shape factor(SF) exceeding 20, (SF=perimeter squared divided by area)
b. extensions over 12 ft
5.2.3.7 Slab-on-ground foundations with piers shall be designed as stiffened soil
supported slabs for heave conditions and as structurally suspended foundations
with the beams and slabs spanning between piers for shrinkage and settlement
conditions. Piers shall not be attached to the slabs or grade beams unless the
connections and foundation systems are designed to account for the uplift forces.
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5.3 Design Procedures for Structurally Suspended Foundations
5.3.1 Structurally suspended floors supported by deep foundations shall be designed in
accordance with applicable building codes.
5.4 Design Procedures for Footing Supported Foundations
5.4.1 Design in accordance with applicable building codes.
5.4.2 Shallow individual or continuous footing foundations should not be used on expansive
soils, unless the superstructure is designed to account for the potential foundation
movement.
5.5 Minimum Foundation Plan and Specification Information
5.5.1 Plans shall be signed and sealed by the engineer of record, and be specific for each site or
lot location. Plans shall identify the client's name and engineer's name, address and
telephone number; and the source and description of the geotechnical data.
5.5.2 The engineer's drawings shall contain as a minimum:
a. a plan view of the foundation locating all major structural components and
reinforcement
b. sufficient information to show details of beams,piers,retaining walls, drainage details,
etc., if such features are integral to the foundation
c. sufficient information for the proper construction and observation by field personnel
d. information or notes addressing minimum perimeter and lot drainage requirements
5.5.3 The engineer's specifications shall include as a minimum:
a. descriptions of the reinforcing or pre-stressing cables and hardware;
b. concrete specifications including compressive strengths;
c. site preparation requirements;
d. notes concerning nearby existing or future vegetation and the required design features to
accommodate these conditions; and
e. the schedule of required construction observations and testing.
5.5.4 The engineer's plan shall address site fill:
a. The plans shall address fill existing at the time of the design or to be placed during
construction of the foundation and shall require any fills which are to support the
bearing elements of the foundation to be tested and approved by a geotechnical engineer
assisted by a qualified laboratory (Bearing elements of a suitably designed slab-on-
ground foundation are defined as the bottoms of exterior or interior stiffener beams.)
b. The plan shall require that a geotechnical engineer issue a summary report describing
the methods, and results of investigation and testing that were used, and a statement that
the existing or placed fills are suitable for support of a shallow soil-supported slab-on-
ground, or that the foundation elements should penetrate the fill to undisturbed material.
See Appendix B for more detailed information on fills.
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Section 6. Construction Phase Observation
6.1 Responsibility for Observations
Construction phase observations and testing shall be performed in accordance with this document.
6.2 Minimum Program of Observation and Testing
At a minimum, foundations should be observed and tested as applicable to determine whether:
a. exposed subgrade soils are prepared in accordance with the plans and specifications;
b. fill material and placement are in accordance with the plans and specifications;
c. pier placement, size and depth meet plans and specifications;
d. foundation elements, including reinforcement, meet plans and specifications immediately
before concrete placement;
e. concrete properties and placement meet plans and specifications;
f. for post tension slabs, stressing meets the specified elongation and stressing load of each
tendon; and.
g. specified site grading and drainage has been constructed.
6.3 Compliance Letter
6.3.1 At the satisfactory accomplishment of all the requirements of the plans and specifications,
the engineer of record shall provide a letter to the client indicating, to the best of his
knowledge (which may be based on observation reports by a qualified delegate as defined
in Section 3.3), the construction of the foundation was in substantial conformance with:
a. the minimum standards of practice presented in this document; and
b. the engineer's plans and specifications including any modifications or alterations
authorized.
6.3.2 A non-compliance letter shall be issued if the construction of the foundation did not meet
the requirements of Section 6.3.1.
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APPENDIX A
IMPACT OF MOISTURE CHANGES ON
EXPANSIVE SOILS
Most problems resulting from expansive soils involve swelling or shrinking as evidenced by upward or
downward movement of the foundation producing distress to the structure. The difference between the
water content at the time of construction and the equilibrium water content is an important consideration.
Potential swell increases with lower initial moisture content, while potential shrinkage increases with
higher initial moisture content. Moisture contents and shrink/swell movements may vary seasonally
even after equilibrium is reached.
Precipitation and evapotranspiration control soil moisture and groundwater levels. A slab will greatly
reduce the evapotranspiration rate beneath the slab and partially reduces the inflow due to precipitation
or irrigation because of groundwater's ability to migrate laterally. Therefore, soils beneath a slab are
frequently wetter than soils at the same depth away from the slab. However, a wet season may result in
wetter conditions away from the slab than under the slab. With time and normal precipitation patterns,
the soil moisture profile will return to its normal condition. Seasonal variations in soil moisture away
from the slab will generally occur fairly quickly. Seasonal variations in soil moisture beneath the slab
will be slower. In addition roots from trees and large vegetation will seasonally remove moisture from
nearby soils.
Wetting of expansive soils beneath slabs can occur as a result of lateral migration or seepage of water
from the outside. It can be aggravated by ponded water resulting from poor drainage around the slab or
landscape watering. Leaking utility lines and excessive watering of soil adjacent to the structure can also
result in foundation heave.
Foundations can experience downward movement as the result of the drying influence of nearby trees.
As trees and large bushes grow, they withdraw greater amounts of water from the soil causing downward
foundation movement. The area near trees removed shortly before construction may be drier and subject
to localized heave.
Some construction and maintenance issues include the following:
a. In general, set top of concrete at least eight inches above final adjacent soil grade for damp
proofing.
b. Provide adequate drainage away from the foundation (minimum five percent slope in the first
tenve feet and minimum two percent slope elsewhere). The bottom of any drainage swale
should not be located within four feet of the foundation. Pervious planting beds should slope
away from the foundation at least two inches per foot. Planting bed edging shall allow water to
drain out of the beds.
c. Gutters or extended roof eaves are recommended, especially under all roof valleys. All
extended eaves or gutter down spouts should extend at least two feet away from the foundation
and past any adjacent planting beds.
d. Avoid placement of trees and large vegetation near foundations (taking into account the water
demands of specific trees and vegetation).
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APPENDIX B
IMPACT OF FILL ON FOUNDATIONS
Section B.1 FILL
Fill is frequently a factor in residential foundation construction. Fill may be placed on a site at various
times. If the fill has been placed prior to the geotechnical investigation, the geotechnical engineer should
note fill in the report. Fill may exist between borings or be undetected during the geotechnical
investigation for a variety of reasons. The investigation becomes more accurate if the borings are more
closely spaced. Occasionally, fill is placed after the geotechnical investigation is completed, and it may
not be detected until foundation excavation is started.
If uncontrolled fill (see discussion below) is discovered later in the construction process, for instance, by
the Inspector after the slab is completely set up and awaiting concrete, great expense may be incurred by
having to remove reinforcing and forms to provide penetration through the fill. Therefore, it is
important to identify such materials and develop a strategy for dealing with them early on in the
construction process. Fill can generally be divided into three types: engineered fill, forming fill, and
uncontrolled fill. These three types of fill are discussed below.
B.1.1 Engineered Fill
Engineered fill is that which has been designed by an engineer to act as a structural element of a
constructed work and has been placed under engineering inspection, usually with density testing.
Engineered fill may be of at least two types. One type is "embankment fill,"which is composed
of the material randomly found on the site, or imported to no particular specification, other than
that it be free of debris and trash. Embankment fill can be used for a number of situations if
properly placed and compacted. "Select fill" is the second type of engineered fill. The term
"select" simply means that the material meets some specification as to gradation and P.I., and
possibly some other material specifications. Normally, it is placed under controlled compaction
with engineer inspection. Examples of select fill could be crushed limestone, specified sand, or
crusher fines which meet the gradation requirements. Select underslab fill is frequently used
under shallow foundations for purposes of providing additional support and stiffness to the
foundation, and replacing a thickness of expansive soil. Engineered fill should meet
specifications prepared by a qualified engineer for a specific project, and includes requirements
for placement, geometry, material, compaction and quality control.
B.1.2 Forming Fill
Forming fill is that which is typically used under residential foundation slabs and is variously
known as sandy loam, river loam or fill dirt. Forming fill is normally not expected to be heavily
compacted, and a designer should not rely on this material for support. The only requirements
are that this material be non-expansive, clean, and that it works easily and stands when cut. If
forming fill happened to be properly compacted and inspected in accordance with an engineering
specification it could be engineered fill.
B.1.3 Uncontrolled Fill
Uncontrolled fill is fill that has been determined to be unsuitable (or has not been proven
suitable) to support a slab-on-ground foundation. Any fill that has not been approved by a
qualified geotechnical engineer in writing shall be considered uncontrolled fill. Uncontrolled fill
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may contain undesirable materials and/or has not been placed under compaction control. Some
problems resulting from uncontrolled fill include gradual settlement, sudden collapse, attraction
of wood ants and termites, corrosion of metallic plumbing pipes, and in some rare cases, site
contamination with toxic or hazardous wastes.
Section B.2 Building on Non-Engineered (Forming Or Uncontrolled)Fill
Foundations shall not be supported by non-engineered fill. To establish soil supported foundations on
non-engineered fill, the typical grid beam stiffened slab foundation is required to penetrate the non-
engineered fill with the perimeter and interior beam bottoms forming footings. Penetration will take the
load supporting elements of the foundation below the unreliable fill. Penetration could be accomplished
by deepened beams, spread footings or piers depending on the depth and the economics of the situation.
Generally, piers are most cost effective once the fill to be penetrated exceeds about three feet, but this
depends on the foundation engineer's judgment and local practice. Floor systems shall be designed to
span between structurally supported foundation elements.
Pre-existing fill may be classified as engineered fill after investigation by the geotechnical engineer. The
approval may depend on the fill thickness, existence of trash and debris, the age of the fill, and the
results of testing and proof rolling. The geotechnical engineer must be able to expressly state after
investigation that the fill is capable of supporting a residential slab-on-ground foundation.
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