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03042004 BSC Agenda Item 6
•`Technical Papers DEVELOPMENT OF DESIGN AND REMEDIAL MEASURES FO, LiG'rfTLY-LOADED STRUCTURES FOUNDED ON EXPANSIVE David A.Eastwood, P"E. S°11-S V41TH TanIdEES RR4icMn jaNKIDW. Peverley, P Geotech Engineenng and Testing,Inc Peveriey Engineering, inc. 800 Victoria Urive 1207 Regency Square, Ste Houston Texas 77022 Houston. Texas 770 . 7 3-6994000 7 i 3-977-0'324 \ -/Crigi-WeiToriFiCairenititeratise in the United tates sh&is there rnay be an ahsence 4 1 approaches for the design of it-4,3110y-loaded structures founded on evansive clay s 1 trees are involved. As a result,irony such structures which have experienced distress of the tact:of 91n consider Oen e the eilf.^..:t of trees in the clesioll of these structures I 1 of this pager are a part of e Houston organization celled the Fgundation Perforrnanoe( 1 One of the activities of ttus Committee i$the irivestigation of the adverse effect that tra aonf dithoisr athcelvvreorrio:ne(11 ofalsotrelet icanetsfat ghtly•tOaded StructureS This paper includes ve resuittts of a literature survey,a review of the Wain 1 foundations whose cause has tst-leri attributed to the presence or andior the rernovl il____(____—;et'-lun recornemendations,aii:i(epairs where trees have been identified as the •riniar i NT RODUCTION ilia Mote which provided data wnich sr Oali trees located SOuto ot Arlington.,Tex:, A significant number of residential bud were con- ocai movements varying Rom 1.2 indite structed in the greater Houston are in the 1950 tbrougn between the end at the summer months 1970 time pettods, Many ot these totiittings we tondo the*ger months, Me univetsti of Te on expansive seWs and on twitting lots,which were void oonducted an investigation el 69 abed& ot vegetation. Trees yoete then pianted atter these bok- buildings which were founded on clay soi Ing Were SOKI and eventually the Imes mauled eat caused among other things,that the extractor)c toundation failure to occur, Corrective measures goer. the soil through ite roots 01 trees, caus ally included isie underpinning Of the inuridatien bean, severe dellKtiocis in loundations.cm in 1 atilt be.am using dliktil piers and later prase+,piles. 'Men presented data whic-I-1 shor*d damage piers were used,this approach had,vibes:,a limited de, caused by trees. Kramer and 1.c.ozowslci give ot success. That/pc ol tailtrre rrode,inherebytrees comparakively high transpiration rates 0 cause the settlerhent 0,the perimeter of residential,and 1960. in 1981, Pelrerley and Hanyel Oltef low-riSebeild'Ogs,has*awed a signsficant amount sure d detections in a residential toundl el publicity in recefit times and. as 3 result non e own- been orodixed tiy nearly,"trees. ers,building rernivielpg contractors,horn buitderS,etc. have become aware nt this pmbiern, F rorn o16:an entire I he manner in which trees can cause dr industry nas grown which provides measures to oontrot tiOnS in residential siah-on-grour4 loundf this nobles) tore,heed well documented. SimPlY sti satisly Mei:need for-soti.i.vater,trees c Some notice ol trie mariner in Which tees can produce soil upon which the outer edge ot a tau dOWnwerd defleCtienS in residential siatrunground too, suiting in the shrinkage ot the seit with 1 dation began to appear in toe early 1970's.. For example, of sPil stiNdit. Foundation distress al in 1972,pavisl,Isurionanzed existing papers Whith indi- Causes h occurred war such(ego Gated that near-by treeS COO adversely alect founcia- Houston area as to have caused a ma ion pedorrnarice Davis and tucken,4 published a'tech- 1tindarnentaf ioundatiOn i.Wign and cot Precentt4 0.1.b.e SP ing SP.SSiOft or.thti Tr:415 ste-iion tit ASCE. i (nick here to continue inttp://geotecheng.com/papers/techpapers lig,htlyloadedt.html 2/1V --■1111111111111111111111111111111111111111111 Technical Papers Page 1 of 2 ✓ v � � °� Y: � a _ } 4 as i � �� • �2 ?e s � " t '< � • " �t' �§ ' ' r 77, m '. - a` a" x;zv�" -- '€F �.€,: �i-'`'`{ .a�.rcr z-iaF tv sF ?y with were in effect thr yeas rib evil tirtderslood. ovule ma-444 to a 6 IMO pa a ied or le be rrr ex- however, arty tiat advoi o eficis that the tiorgnatt t7 isge Ce=Csf 24i t nvian ido4i g it one were tp minservatzm tf 044 Can have Ora rcie Shictad fourhlab aril O*Nana ell=rnate that only of these fourdatron faluirea were they are ream on drilled ors. Eque4 misunderstood caused by trees,the boots wuutit tes obviozsty enormous. • is the relationship between tree root growth and+rndni .,.`. 4 sit war leiiiks. trues are the largest plats t the world Trues can Donoratly be cla cilicd noodle-teal or broad leaf l,o- • T h u pitspose e t this paper is to explore,t h o adverse et- r i r r v s) The essential palls Ufa tree are the crone,the. twit that tress r4s1 have on esAeeual€tur`sdatirn Odor. tr xrat,,3nd Ile;roots. Iry down rL u s tizzies weru,�n der based on the airetiencect oa=ts as r r to d essentially at;; stir:settle and evens at into Idod I he In the literature,based on IA piN WAN aXpOtieme tt Me rods ate Itie fasted #i#i )cart of tree. They coliect r � 4 authors, and based d on an accumulation of information water Arad transport it through the hunk for the leaves in form the Foundation Performance Committee. This pa: the form of sap, The trunk provides the transporting Y per wilt be presented in the tree MOWN bas parts, merchant=between tie leaves and reOte and le' Made Mutation edge ttlement produced by bpd shrink areg. op or the heartwood in the center,the camititen layer at � Wadable Hearing r+ f by toil tkrap,and a the retries u of trlifrilr the bark; provide* tz, ! • dawn' Ater aediefrient catmd by the all' e:on tie- the r4trhany pro€ boe. its grew only as felt as troy Moan If tools and strider-slab soma leaks The m e- se provided sotargy from the loaves_ The to gySZIII ChaliaS of such conditions along with proposed r m consists of the circulation of water from the roots u Svc d 'r h : ;� tired ens mat mil be discussed Ex s wilt be pre- through their trunk in Ito form of sup. When the sap rltor: roaches a loaf, the water evaporates into the air The sap brings mineral salts from the earth to the leaves, The SOIL MECHANICS AS AFFECTE1t BY TREES r tprophyy in the leaves acts'with sunlight to convet the calls into food through photOSpthe s, This food then .1ti'$ A,:1 flows back Pt the tree system thw et e the bark. ft is this system which makes a fire kvo, Trees have been rtni drecf to be a Ott to seer kind Trees have beers widen then about air marry as iittrag toanrgineering tears ,we On primarily concerned with the o y rr f,t years Nam-Trues absorb heal as they temperate.pro- terser evapolransparatfont i.e,the withdrawal of moisture 0000 fir'±�!['rrs sir, vide orate, aid reduce solar r iation_ They enhance from the amid and its eventual trap tationInto the�- air purification aid in the control of erosion, and cart,to a where, Al is have been made to quatrtjfy Wit term;: Y knifed degree, prcxvide a reduction medic. former,he results have not sways�uniformly .. ; .�s t most appreciated d� t is time/amity to +meted the divalent*extorts, renumt e,WO* Ennberice tyre beauty of tbe ,etwr'rof erg landeupe. One setts lac arse of tie n; ytety to aodkaratrrty mesasur the can appreciate the beauty of old oaks Wilose branches Moisture lossfreplacernents in the soil under mod trees provide are unthrga for many of the roads In the oki South Oriscoltoli presented d a ranking of trees in terms of their or vehose multature enhances the skykne of the Pacific damage potential,A magi icl copy of this ranking is den- Coast: tamped in Tabfo i tree rues do have the eery- ;e! Tires tars fit WIN to the greats Horziort atoa, we do not have an abun- properly and t om` la the GiAbtrett p000fo t u n e been d ;-e of Popia trees;however,there welt may be more injured or killed by falling trees Tree o roots clog sewers Oak trees than any Quiets, At SOntaried ire ha dew- and break sidewalks. Trues can also.ricrea$ra the ozime merit is art example of; aaonat moisture content w ra, content of the ,damage electrical power linos,and in- insiss,which rs shown err Figure t O interest is the idol- team with Ul-reception. Perhaps the highest cost of brication M a toned permanent moisture deridency.This trees is in their damage to rettdientil foundations In 1g73, cunoept was lihthor explored by Riddle')')whiz measured Jones and Hat see arlirnaled the annual exist of expari, the sot mntr_r,care content tea the dose proximity of v, irk UN's RON in the tl i In be c 2 billion dollars In 19w. kinds, of sees *h al vote growing in a v iety of clay F'r, r-gtoy&ilanys eSthlattN1 aut repair rhof.,e mot.all of- oh Were vs E_recjtark4 A COintinad moisture residential lowed:Sams arcs in the greetnr i buskin,1 -a s roil rt tetmfrroi ctwe deficit curie for a Poplar iir tree growing 2 ttp://geotecheng.corn/papers/techpapers 1ightlyloaded2.html 2/10/2004 Technical Papers Page 2 of 3 - Table 1. Risk of damage by different varieties of tree I Ranking I Speruisi I Matirrium might o 1 beparaon oetweari 1 mina-num reciorrm I I i tree OA).metres I triaiia arid titailoIng4or j iti shrinkable Clay: ri I 15%of mt,..- :metes f I— I ... Oak 1 t 13 I i 16-23 i ill 41 1, I 2 Rapia! 24 } 15 1 01 16-24 a i u 511 - - - - t- ' --i------- . Li. 1,Common Ash 23 I0 I 0 5H -------- } - 5 Plane 25-30 7.5 0,514 6 I Wilma i 15 7 Elm 1 20-25 12 0,511 $ Hawthorn 10 7 0.5H 4 Manila/Sycamore 17-24 9 0.5H .. a , ie Charts JPItirri 6 5 i 1H Botch 20 ri11111.11111111111 0. -- 11 5H 1j2 Birch 12-14 7 r 4151 I White&MT owe A i 5-12 7 Iti "1- _ rja.L_ _ Sms,s i 16-215 ae OSH 15 i.iP :--- -„ii.,-;, .1cLi%-\-a--. ,0 .bia.' , ' lrA4114414;i1-7 S. i) .;,, ,-.,.: ... .■ - .;°.--7"1:!''''''-;:::',..4.''',,X`''...;0:4-1AV. V .• ,„,- " , 't ;1,.,* ^- /NT. peasmows0 0056,1, ' . 40 ,, i Av9e,ro 00901 Of y i 4414 ....... . ,„A„,.....4„, 4,.... 1'7 ' 1 14 i 4 f "4 —....,...., .r......._,....,....„......_„_,.......,..t_____ — ....0 09101001 .41 iii--.............•....."'"',._:,'.......,..„.„3",,,,"'";_,,,,,,,, ,,,,,,,,,,,.7....--.. 19 49 Wi .0, tilt 10 36 49 1,9400...9 0901,9 li“ 00,,,e,,ne.,....i re.) INF ..t..._, Figure 1.Seasonal venation in moisture content eta and with. Figur*2. M taarnpie°twit moisture and e oi.4 treea :Week:a climes for popular trate art:bad London.England in a Bolder Clay (Pi = 29%)is shown in Figure 2. The moisture deficit curves are calculated by multiplying the trees closer to buildings,assuming the i change in moisture content by the appropriate layer thick- these curves are considered. They also ness, in reviewing this curve, it is significant that it does folly of simply removing existing trees ir represent the most severe condition for a tree which has for the construction of a new residential been judged 10 be of a lesser threat than would be en Oak tree growing in a so P whose Plasticity Index Is less WHAT CAIJ$ES EXPANI$Piik SULS i than some of the major seas in the greater Houston, SWELL Texas area The availability of such data in .riglarid has had significant Impacts on the construchon business. As clay panicies are formed, there art Whereas h was cerisinered to be inprecticai to plant any points in the petit:to arrangement where tree dieser in a foundation then it ultimate height,these ifical irnbatanOe; the electrical imbelai data do provide some bases for the ptanting of certain whenever a'aiing'of day particies is bit 3 cilck here to continue http://geotecheng.coni/papers/techpapers _lightlytoaded3.html 2/10/2004 Technical_ Papers Page 2 of 3 the result is !fiat a clay particle typically has a negative nedative pressure (expressed as a poi net electrical charge on its surface. Since nature likes all rive to ambient atmospheric pressure things to be balanced,whenever a water molecule drifts which solution Identical in corrgzsition dose enough to the surface of a day particle,the nega- must be subjected in order to be in equi lively Oiarged surface of the clay particle causes the pc - porous permeable wall with soil water: live end of the water molecule to turn toward the particle lent to permeable wait with the soil war if it is dose enough to the particle,the water molecule is equivalent to that measured by test mei attracted to the clay particle surfacci suff,ciently strongly 03152. that the water molecule becomes trapped. unat- tached or 'free'posdively charged parlides, called'cat- The osmotic suction is the negative pre ions',lend to acquire a spherical-shaped arrangement of pool of pure water must be subfected water molecules‘iitiich have their negative ends directed equilibrium through a serre-permeable r toward the positively charged cation and their positive pool containing a solution identical in ends directed away from the cation). itthen the free cat- soil water;decrease in relative humidity ion is;captured',.water molecules approach a day par- sure of dissolved salts in pore-water. ticie. The attraction between the negatively charged day particle surface and the positively charged outside of the FOUNDATIONS AND Ri eiitori where ufwalut niraluoules cause iYi ation to im °capured'by Ina day particle,:WS irief G&sing the ainaint Many lightly loaded foundations are d of water associala with the clay particle. structed on the bas of eCOnOilliCS,risk dation shape and structural loading. NI, Clay particles am very 2.11. A typ-iCal actir.ito pertide socrvnic considor aliens l'Jher is right have a ttal el-2f= area(tW, bottom and edges) foundation desigm Most of the time,te f appmoximnatety 1 t 10-5 rnrn2 (1 x 10-10 ft7, or are selected14!he owner/builder,etc. !I 0.0000000001 12). As areas go, this le very sml!. that some levels of risk are associated P,rrioclite partldes have a diameter that ig 100 to 1,000 teundntions and them is no Botch ng litres srnabr than k2olinite pert arid a thickness That dation. Alt of these fel inclations must b iR in to 40n times thinner than knalinital'4 and masa- areas where expansive snits are prase' quently,typically have a larger surface area per particle. been removed prior to construction, The Thus, a single pound of rriontrnorillonite particles would typically used in the area with increas have ar incredible fetal surface area or approximately BOO and decreasing levels of cost are discu acres p25 hectares)Int with which to attract water. The above recommendations, with re, Thus,expansive soils are very small in size and have a foundation types and risks, we very g( large surface area that attracts free water. Because of type of foundation may vary as a func these characteristics, it is easy to see why it is said that loading and MA types For example, expansive soils are those days that exhibit an extreme floating slab foundation may perform be change in volume, footing type foundation. Soil suction is a measure of free energy of the pore-water FOUNDATION PROBLEMS CAUS or tension stress exerted on the pore-water by soil ma- trix. Soil suction is. in Practical terra, a measure of the FOUNDATION SETTLEMENT PROM. affinity of the soils to retain water and can provide infer SHRINKAGE mation on soil parameters that are influenced by soil wa- ter;e.g,,volume change,detOrmation,and strength char- Several authors as far back as 1960 h acieristics of soil. The soil suction is rneasared using the this type ot distress.0.141 auckerv.pro filler paper method in accordance with ASTivi 0-52ga to placed no closer to a residential fot ultimate height. The basis for this rec Trio ail suction is divided into two components; Matrix contained in Figure 3.it was not, howev usinutiu suction. Tile triairiA budjupt i tits nized by the designers and consirucior8 4 ic k.here to continue iitip://geoteeheng.eorn/papers/techpapers lightlyloaded4.h t nI 2/10/2004 Technical Papers Page 2 of 3 tante Ii. r ',!hic tr.-,of four.4-Ahon tirdtitch Alv■.iniurtee A'pi■tv arid b 1 ntructrat Stab vitt Piers teitiedanoti with a craut ewe)ts consirkred to be a mini A miter-am Crawl sptce Of..',/,x-'' ,A,;;:ikes or targ i bird Usirkg th4s,ktrot-tv40"3,Olt txxr SilitA NO rgli an Ii Voiti ris0 :trigii----aitts STA& Mi3 type of buri,, ,tiori is ..-'oci 1 vlitiy1 kr glw„trtv velfArti AzparMivip iriag we fwergent en• 1 1 tees haul been rammed prig to construction. The dna I icobitgs must be plar#04 Wow the potential active zone; I minimize poiianuar. : reeled"kinking upheaval die to evens ! fa the areas utpie a non-a:Rimer-a 34**a Fasant 4,7:: [ frinbritis cse he used instead of drilled footings 6teio-Ort-Fiii-Fouriciadon.&moiled un Pli-as I This foundaion system is also suited for the area whEre I sods we present This system has some risks with woo 1 1 I foundation dishes end movements,where expansive a( I present ven A positive drainage and veverialion a 1 I ;,-st,•-dad,210--Pm of tottr&tim ele:sild perfettn s?...tis fa.c! 1 1111 tidiness is eve/anted such that once it is cornbinedc 1 11 I tat conditions{positive drainage,vegetation r.ranimi)the i I vettical rts.141 be minimum. The sired:twat loads can* ' i supdteirti on spotai Lint*it***Isles snits are rocd i 1............=■••■••■•■••••■•■•=isomb...........w.................s..- I Floating(Stliferied)Slab Stonfilixt on Piers. The Slab can 1 The fi4,ba iiis bye tii ituurviatit)a 4yslerr.tan be reduot either be ConventionairpiReinkarced or Post-Tensionesi I if A re'hitt ettct r&tintirtect iAtiri positikte ctru kluge end ve l cntrol. Due to presence&piers,the slab can move up ewansive wits are present,hirtmt down. in this case, 1 ton the*Mediates should not be deviated into the gra I 1 The Wicks*trait,oar,gee be waled at w-eoci fo a., :_nsive casein rigi rime*. IWAvIrTr:Si tab Fr,,,;...,-,01.0.,inn r-frennti*ty-Reinfavid al Pont- The risk eei this type of foundation can be reduced signif i Tensioned Stabl is built and maintained with poslOve train And vegeb I conati Sepias are used in this*lee el rounciaiion ky I lightly-loashichaso in the sta.1,`4,of Tam a's Witt on t er foodation and are orifecrnin,o.satisfactorily, fn the ot tees have been removeriprior to construction and whet I[ eXpOr‘ve clays exist,These foundations must be signific stiffened to minimize ihe potential died-ennui movement [ -- =At 0 etteall.43V2 fide le tee ft-rViat, homes built on concrete slab-on-ground foundations in __. _ • .-- ,...,. the 1950 time period. In Houston,Texas,as an example, f t the posi World War It building boom included upwards of cs .1,- 100,000 homes constructed in the Southwest pat of the k r .\ : City,where the soils WellEt typically very elpansive. in i 'i.- Ylt, . ..,“ most cases, these homes were initiany constructed in i • - i. .1 subdivisions outside of the City limits,but were iater an- z " - c g =. N .• e044•ttit••••„, flexed by the City Thus,no building oodles were applied. g Since this real estate was largely farm land Mich was i " t: - .....•..' -. . barren of Maas,one of the things that were done by indi- * •- ' " dual homeovw-lers(end even some subdivision level- ...., . . „,- . . capers)was to piwt trees in the yard clow to the lounda t - Soo. Trees such as Oaks,China Berry,and Paean;wiz " popular because se they were hardy. When the toes on- r.AAToo „ratt int, :lair para of mole; wrath, their wafer ott.,_ Ftgure 3, A curve el foundation vertical movement 1 WWII rrkarItt SU)adily inacasiclf and foundation problems be- gan, .N-li ir4^ de se—ated et the tirul,'ci =rmtructier wilt rP.r-ve tove,rd the.,/enter nf the t•te, .--zdis de "have sthr,'wn that When ° I 31!) Ar-- ,t-4 on Ng he ilt,1 the edge. Trees uize stil moistme ground, ekr-lpor4eri of V:kil Minis:tune is retarded. II the TherAfote, during we parbtiS, tattficiant!Cupp S http://geotecheng com/papers/techpapers lightlyloaded5.html 2/10/2004 Technical Papers Page 2 of 3 hr e is Neitehle for tree growth and snit moisture con- Figure 4 shows an example of a home !wet tepee may not be substantially affected by vegetation, Southwest part of Houston,Texas,*nose slab-c During dry summer months,when evaporation rates are foundation was underpinned using drilled pier. high.the trees will obtain atae quantities of moisture from the 19; to 1990 drought, the foundation incur alroacty dry wilz. If these trees are located in dose pox- tional deflections. At our suggestion,a root ban irnity to lightly-loaded structures such as houses, their tined with an automatically actuated soaker sy: mot system will move toward the structures,in an attempt applied,and the foundation not only stabilized, to tied a moisture supply. if trees are too dose to a house, rebound occurred. The example contained in F desktation of the eoils below the stab may occur,caus- riot, unfortunately, an isolated example. Beni trig settlement of the slab have been obtained in the recent past using pre mooted piles and helical piers,r4, 'Vertical moisi ere have enjoyed a very Fleeted use, cocrepukk'WM%U r-7-71 POUNDarICal Ow me tbin 1 1 ip\ \J FOUNDATION_EDGE FICAVING. CALISED SWELLING 1 -11 1 e---1 1 I \I r.,..„.., — - -- i i Tv wripensete for the settlement.of the outer I --.,..... \ I foundation due to the ex:extort of rneicturo fro e,„ \ 1 through the roots of nearby toes,aft eeeepted 1 .e-e'--., - ---,_ `ee -----",--, \`‘-..\ 1 live reeesurc erm to pi2Cfl the foundeseo or irl Oars. Most recently,however,a eentlitieri has r f ------,,,,,,,7,,,,,,.."- -„,..,,--,1 , / ,..... -.......---,... -....-A eetere the piers became a detriment, In the in the City V Houston, Texae, there are subdivk cornpaeative,ly email building lots, which often ..../..-....„.....„ ra---`-`e, _week elder homes, became very desirable h l' 3 their location, In many cases. the lots conlair 0 0 prolific trees,which were removed to make w i i 1 c) construction of larger homes. In many such ca ing was done to compensate for the inevitable i ree,:eeekere;ea 1-1-7-1 the soils which would occur when the tree, I eieeterutatuawr 1 eeiccaled the soil in its near vicinity, was gen r) z N suction forces moved soil water into the desii 1 11 \ I eas. It does not lake much imagination to ir I . mood of a homeowner who, ki many cases, I )i if I moneys to have a shirty foundation construe! 1 \ / 1 have it begin to move soon after the owner mo 1 I ( 1 example of such a condition is shown in Figu \i,. '' --e. foundation,In this example,was founded on 10 1 e 4.----..._'°- -'''''`e. I drilled piers,which had 42-inch diameter bells inspected during construction, The pier shatt 1----Le .ej 6-----1, I 1 to the concrete perimeter beam,The soils had index in the tiu%range_ A Pecan tree was re .1.11.6....impecilill■frinaMaiii....alk... ing the constructioe process,or shorty thereat f 0 t ? o el foundation induced damage became rewire 1, J k / the iirsi year ci con sauctiori and have, In Itl• \--ee 2 \--,„_.----e worst3ned steetiiiy, A literature eearca-4, false arty doeureented diedieskin of this phorterteenc Fevre A An 40.,..nvtn og tri/rIre 9! itliirtillAIim es,a result of iii ti a stele a Texas, but in to United Stete the depletion of moisture at the edges because et trees, r...-.4, 9;,,,s.-....1.n.,'Ls 6 a..1 e. 1.-.-1,-..1,-7,,rar fed Irv;in tiler thasuremerita were takers alter pier Installation am!after root '3"..''L,',.`",a.'''-'"-."'''''.•'"'""'"',found *-,-. barrier instaltation eulstde of'ID'United Stelae. A!IF:Ping of tge+i 6 eve. !lel e to coni;ni http://geotec heng.eorn/papers/tecit papers lightly loaded6.hal ll 2/10/2004 Technical Papers Page 2 of 3 contained in the Ba)frography Section a this Pager, This Eignirr.411CAI of the U00 IMITIOVa situafron is perhaps best t , I illustrated in Figure en, In this case, the removal of a I Poplar tree caused over 6 inches of heaving which was irj r r monitored over a 30-year period of tirrie, Li , I I 11 i i Lr 1 -- J -1.• ) Eilli 6 It Ai . it 4- ' " \---• 11 kftP666 . , Lp,a5Ci i jib-L--, 11-Ta 1 gm ,..,..., III-ii-1 ' I 1 r . --, i _.,...._ _I _ A. 1 / 00400 )1. 444I V 14 k II 14 T a T Ir 't 1 j----- 0— 0 NW 4 . I 4 a ' 1 t i 1 ..,,, -----,.,.:-.-,==.'":•-=",,,,.,,'.- \N. e---or 8,14 1 : .,....,.......„_. -7... ...- ):11,.).\\. t ft $ 14 in 011 04 100044 Si MCI Figure S. 441 example of a home*Nth had been adverwry effected by the rernevat of a Pc 2111 tree = Wm,Osinme*uot tervid044*V totoinv m.00mogowo vorr. • ? *:' il-r-2:*-t7,?,-.1.-241-4P-4,0 rigwe 7. An=ausrote of 3 home lft Houston,Tex"wttl bad laa i 1 •sI iic 11 / J ----- tl.t77.t)guftc'els ere1:7e:or"liovarsedroilhor'actwawaPa:dr.e:sid2:ttec:tnt,ialbwebu:soriliedi:th;asihtin:plaWstoff:Or: — ., • . struction,had Post Oak trees on aither side. The remotes ;II I of the trees caused significant heaving of the foundation r I .------- c 1 at the rear of this,and several other buildings,which were constructed along this roadway_ We have been able ti measure heaving in a limited number of cases and Mr results are contained in rime Et.. In comparing our dati 0...ii......, with that shown in Figure 9,we can see that the slope o our data is sleeper,even though one of the curves se"ei miff— Eimri , F 6 -11 Lllia- nil to level out after 7 years, or......_-2-.__w.,..----- I-4404447A 040444 el 104, 0440 00 As mentioned earlier,tree roots tend 10 desiccate the soil kr In the event that the tree has been removed prior to build Figure 6. A cep/era v011iCai rilOvernerit that occurred as a ing cmsfrudion,during the useful life of the structure,o 1 msua cer the removal of a Poplar lit in London,England if a tree dies, subsoil swelling can occur in the expansvi 7 http://geotecherig.com/papers/techpapers lightly I oaded7.htm I • 2/10/2004 '. Technical Papers Page 2 of 3 1--------r------------- hI 'rho pier depth could be ax.h.• that it could resist the I ---kiSsr.r.S+.10.19 me PL1:1 LIT'rHE,,C.1,t41 --—nr.X4TAAN f.0.4 1•VAi,RIAL.rt%,..C.,,,ow ----mouls/ZA Mott.-.A.Itt,ek.f.t.er k 4 iih-fl* ----MataTOW 0111MO.P^Ot EttorOW5.1 0..1 , 1,10,A k.)ad,S,due to expensive soils that extend along the shaft perimeter. 1 ' ..-------- 1 i 1 V. ,i , i .,__...-- ---- --- c) More wensive soil tests are required. Soil borings P L! 3 T -- - - .,,,--- t I f-r--- ... . . . , . 8 . , 4 . WM lio imuti near a tree must be, as a minimum 25 to 30 feet deep. The depth to which tree root fibers exist must be determined since they are a basis of identifying the depth of constant soil suction. Potential'Venice! Movement values should also be calculated. In the event that a floating slab foundation is used, we recommend the stab be stiffened to resist the subsoil Fillet-€.8. movements due to the presence of trees, in addition=the area within the tree root zone may have to be chemically =bltzed to reduce the potential movements.Nternatively, p --; I I, „."--' 411." the site should be left alone for several years so hat the Illoitm 0 ta..A. iksr i "'1,_,„.„„. .._,.,,,,,,,,,, ,_ . . moisture r in the tie desiccated soglccated area of the s(whee ...- ----- - - if roots used to be)become equalized/stabilized to the . * .. . . * . 1.1.0.40.9r* surrounding subsoil moisture(motions. The length of ---j , lime required for subsoils to regairt their moisture is de- _,.......-..„::-.:..„ pendent o the tree species,soil type and the amount of tz z ,___,,,\-\\,‘ rainfall. For most trees,one wet season may be enough for the subsoils to regain their moisture;hOWeVer,removal of trees such as Live Oak,Poplar,etc.may result in tTiOiS- ,.44. tura defidts in the soil profile that may require several if* years to stabilize. ' ( \ ) Remedial measures to=Ted the adverse effects of this type of soil heaving are somewhat limited.One method is ( to raise the entire foundation out of the potential vertical . r. _ , 0 _....1(' 1-..- -',4 • 0 0 ta'risgew°i1f1 the soil u sisZwundthee(PFYvmif"npgoiechtentiainiqVeuerstie. Soil otevste.- . merit)values in the soil where the trees were removed. It may then become necessary to raise the foundation out of this zone. An alternative)is to use a vertical Mirage barrier. A combination of partial underpinning and the Figure iii, use of Moisture barriers may also have to be used to stabilize the foundation system. sal areas for several years. Studies have shown that this process can take several years in the area where FOUNDATION CENTER SETTLEMENT highly expensive days are present, In this case,the foun dation for the structure should be designed for the ariliri- . . `I ' ' There has been an ever-increasing problem with regard paled maximum heave. Furthermore,the drilled footings, - to the interaction between trees and foundation perfor- if used, must be placed below the -one of influence of mance, ie. foundation performance induced by tinder- tree roots. This depth should be evaluated as fellows, ' ,. slab sower leaks. Many of the homes constructed in the 1960 limo period had cast iron,under-slab sewer pipes a) The pier thoutcl be placed below the depth of con- . boned in clay soil. Over the past 40(f)years the effect of slant suction or the zero movement line this unfortunate marriage has produced a proliferation of /3 Click here to continue ittp://geotecheng.cornipapersitechpapers lightl yloaded8.html 2/10/2004 Technical Papers Page 2 of 3 under-F4ab sewer le4s SinC6 roost lit not )of the home the ultimate result that the foundation stibmded irtstead inserance policies allow a nomeovener to collect on dam- of heaving, as ono might anticipate: agos by such teaks„there has been an attendant number of such claims filed. This opinion does,of course,involve a number of assump- tions for Which no proof exists to fact,there is little of no Typically, the insurance cai nor hires a plumbing testing real proof that any sewer teak did,or did not,cause four many and an Engineer to determine if the leak has dation deflections to occur. More testing and study is caused any foundation related dame, it is likewise typi- required cat that this Male Engineer will observe that the founda- tion has deflected downward in its miter section,which CONCLUSIONS AND RECOMfirIENDATIONS is the opposite of what one might anticipate if wa ter were to be inducsd into expansive i€&. Other contradictions The design and manufacttrreof most 01 the material hint..s may be observed Which included the following.: we use in our lives is based,to at least some degree,on o The timing of the damage appeared Sonie type of research. Automobiles are designed and p ared c�identat to extensively tested before they reach the market .manu- the occurrence of the sewer lBFyk, lecturers of appliances subject them to extensive testing c There were plumbing teaks;yet,watrere soil tests were before s must be given extensive testing,,ee, new food o prod- rxrnrduratod, the soils were comparatively d e `'�,etc,It is then�- dry what ignominious that the design and construction ction of the o There was always a reasonable degree of ccatrete- investment for most what f of us is b on px pensive bon between the pr-eson of the sewer teaks ,d research; at least in the United States, Instead,we tend the points of deflection to team ki the most fundamental, and in the crudest,of ways-by trial and error. The cost of process is born a to a majority of cases the sails were expansive,the by the builders homeowners,and engineers much to the foundation was constructed on drilled piers or was delight of many attorneys. underpinned using drilled piers subsequent tote time of origin construction, and there were trees grow- We have,in this paper,pointed out some of the probe ing near the foundation vibidf were almost always that can be caused by mature. It is a known fact that the water demands of in urban environ t Alt g auc to h of li re's di tree mature trees lend to stabilize, Could these bees then sion was based on t-tousion,Texas, experience, thi in suddenly beano the source of additional fotmda. formation certainly applies to MuCh of texas and b other lion ftecliOns? parts of the country,as welt, All of us who are involved in low- () in the (4)cases which we examined,the forego- rise buildings need to bed cognizant of these or other w- ing conditions existed and the foundation Bellied in to conduct ourselves accordingly This may require add- the center instead of waving, as was anticipated. tional pre-construction testing and may necessitate the example is shown in Figure g_ In this case, the need for more expensive designs. Some may say that sewer system could not bo tasted since it would hold OUT clients may not be willing to pay the price for such no water.. extra work, So long as there are en ineers ing to do cheap work, 4l who are will We are of the opinion that the introduction of the sower will recur we will l ft to ponder arse wi s ed people water spurred the growth of the tree rots to grow to- are more wiling to r eymore some pe pie wads the source,n . &i The tree roots then extracted not their engineers and pay builders. attorneys n-�are iii ire they are only the molt:hire provided born any sewer leaks which occurred,but also any moisture which was in the soil be- We have pointed out the need for research. To the best fore the leak erred. The presence of an under-slab of our knowledge,the last 2 large research studies con-- Sewer Leak then resulted in a net soil moisture loss whore ducted on residential foundation issues wore the BRA large trees were growing adjacent to the foundation with in the 1950's and the University of Texas at Arlington stud- 9 Click here to continue //geotecheng.com/papers/techpapers lightlyloaded9.html 2/10/2004 11:'echnical Papers Page 2 of 3 ies in the 1970's. We do knew of some sr tiller st dies„ is Sexton of the American Society of Caw t which have been ducted at some Universities,but we Dotter 2. 1987. nginows, believe that larger studies ate needed not only on the issues presented t€d herein but on sister rues, as woe. . rr 4 ,Richard* 4 tr r Prot Carz r Some of study areas ate listed below Try tvrriti f9 ; : t o A te[atic�i r needs to developed pee>ttat would mss,0,-E. it 1, G.:Expansive Sods=The Hid- dress the tree type(species),distance from the fbu den Disaster,[ it � 3�+tar#?, .43,No.8,Nerve dation, and height of the tree. Yo ,rk,N1 tut, 1gT , ` 51:. o Studies similar to those conducted by Biddle should 9. Traces,trddr,r+ r ;, ,a, 1967, be done rasing trees more typically found in the United Volum 7 Pg States(Oaks,Pecans,China Berry,elo),:in clay soils and varying APather patterns that are t nicat of this 10. R. ()ri t The influence of vegetation on the swelling a luntty, and drinking of clay soils in Britain, The R y el U,. tati'ft rn lw-s The Institution of Ciet Engineers, o How to better design floating slabs that r� ulcl resist Thomas Telford Ltd,1gt . the effect of trees, 11 T t,F gran,et al:Has Yeti wfouse t r lion of Civil ; tt neets Solving . h : l3t alto Develop a simple mathematical module that would Thomas Telford House, 1944 Pg,20 relate sower leaks,tree moisture removal, and t.0 sot( movements 12. P G.Ord e;Patterns of sal drying,n and moisture deficit in Perhaps information contained herein will help in the �t to of trees on day snits, The influt nee Hof search for research dollars, ,The rrsflRrrtion of CtwRt Engineers, r rnas Telford,Ltd., 1 . 5.0 l l t f0 t l�d 13- ' "dy, Wane K a Yoc f# +e is Soils;ASCE Ptbiicati an,1995, 1. Robert C.Davis,P S Oti Eola.d.hon Per'. . The Construction �,ar r Center, The Unwe ty of 1d: Godfrey,b r s b n:az srd, and Winking"moils Texas at Arlington September 1, 1972, prgablerna 3 eirrg attaciceci? ! �?r�� { t€ r 1474, 2. Robert C.Davis&Richard l:.Tucker The Use ot Trees as leas Marks in Expansive Clays Technical Note, ti3 Tucker f ctu L p Arthur l{ ,4s Mapping Division Journal of the,�trrrdar c a idly of Civil o St s Ft�s s on R eta. :* 1 of the Ertl.:r rs � t .l �itai Division of ASCE,mil, 1978. t 5 Dutton,Jim:Foundation Fair Techniques,Ernest E c[ey kn9 � g and l�n!er r 3f t g Foundation lon re.rr Residential Stn r-Greur f Foundations.College r Committee, 1966.Engineering University of Texas at Arlington,March 12, 1974. 17; + lion.t Fre tan et al:Has lots i-lotisr, Ctacks; of C Engineers&Wilting Research Estebtishinent d. Ernest fa Irr Ides and Damage on Roddsnad Slat- ► a T€ House„ 9 t, .24 on- r�Foundations,C r sruutic ri Research Center, Coltage at EnOnfeering.UmewS4 of Texas Mirigtar, t 8; Lawson,M.&C?Cana March 12, 1974 t3,D;A Critical s of l (Tale of Trees tn D irge to Low Rise Buildngs,Journal J, Kr v Ti tie T. Kozlowski:PULi sic s 21(2),Pgs tom,4�. itteA.Pp 29$,McGraw Hill Boxak Company. 1980. 19_ Personal communication rwith or_Ronald tiew,tort Texa :Has t Cam_ MN! Forestry,DeartrmtE. P a y n air t i t rim siniction Rouen-is Prresonted at the Fall Meeting of tt 10 Click here to return to first page ://geotecheng.com/papers/techpapers lightlyloadedI0.html 2/10/2004 u-eotecnmcal Engineeringand Testing provides Soil Testing Enviromental Engineering Geotechnical En... Page 1 of 2 re 1 .'_ .ea z �. w4a �L�"�.����€ �'���� § ,N4� °fy�'�" d r� �°'�t,-, : c� usr 5 � "� s�`a�"Y U 1-K�� �.: 'r•a.ash .g ''' - �. vim'. S t r ' `r ., ti,1,-,s i,i as "-4. ;ti .it rrif, z a 0 t. r 3 -t '7t . t�..ro'°. �t_ 7, r,-' tc`'^ s` Fz �.,,r- it-- �.� 3f .�s .,.,4t?,', , , �'`.#�.... .ate A-<„:..-: � e �m Engineering and Testing F ounded in 1085, Geotech Engineering and Testing (GET) is a multi-disciplined organization of registered engineers, geologist, field and laboratory technicians, and clerical personnel who $. a - l combine their technical capabilities, past experience, gayr":24,4-p.. ,17.4,,124.1;:,,, , dedication, and enthusiasm to offer the finest service ' . : x �,:?" through integrated team effort. GET has a staff of about .M 50 engineers, geologists, technicians, and support staff. ��� Our services include the following: r , - _ fi A °"t'''.1'•gib:1!" :.[111-7-4.0 q _ �: yn. .�£3 Geotechnical Engineering including soil borings . z * � and laboratory testing, engineering analysis and F, a recommendations regarding foundations, paving, F�7 y construction, slope stability, faulting, etc. • Construction Materials Engineering including earthwork, asphalt, steel, and concrete testing during construction. • Forensic Engineering, including foundation,retaining walls, slopes and paving distress studies. k e Environmental Engineering including environmental site assessments, monitor well 3 r Y w�f installations, and underground storage tank contamination studies. op t`qj _: ,11 anl14- 9saeivalatayzEfsterrse _ 3 kigf4 T GET has been certified as a Historically Underutilized Business(HUB)and Disadvantaged Business Enterprise(DBE)with the State of Texas, Texas Department of Transportation, Houston Independent School District and the Cities and Transit Authorities in Houston, Dallas, San Antonio, Austin and Beaumont. *� P 4 Insurance Our insurance coverage includes$1,000,000 general { 3 f liability insurance, auto, and worker's compensation. In ' . addition, we carry professional liability insurance with errors and omissions with a $1,000,000 limit. GET smaintains workers compensation and employers liability insurance in conformance with applicable state law. Furthermore,we maintain comprehensive general liability and automobile liability insurance with bodily injury and property damage.A certificate of insurance can be supplied evidencing such coverage )://geotecheng.com/index.html 2/10/2004 STATE OF PRACTICE OF GEOTECHNICAL ENGINEERING FOR DESIGN OF CUSTOM HOMES IN THE HOUSTON AREA BETWEEN 1990 AND 2001 BY B Y DAVID A. EASTWOOD, P.E..` BY FRANK ONG, P.E. PRESENTED AT FOUNDATION PERFORMANCE ASSOCIATION MEETING ON JUNE 20, 2001 Abstract Practice of geotechnical engineering in the Houston area has been quite interesting during the past decade, depending on the firm, recommendations for design of custom residential homes vary quite a bit. The purpose of this paper is to look at various design approaches and recommendations. This paper summarizes the state of practice for the past decade. Furthermore, the paper recommends procedures to conduct better geotechnical exploration for custom residential projects in the Houston area. Introduction Due to the strong economy, custom homes are being constructed all over the Houston area. Most of these homes are supported on drilled footing type foundations. The focus of this paper is primarily on the design of homes on drilled footings. Many odd shaped homes (U, L shaped or houses with large slabs with notches) are supported on drilled footings. Furthermore, some of these houses have major foundation problems. The purpose of this paper is to review and summarize 99 geotechnical reports in the Houston area, look at various soil types, discussion of risks, heave computations, drilled footing depths, various slab designs, evaluation of environmental conditions, etc. These reports were conducted by 17 different firms located in the Houston area. About 10% of these reports were cuitducted by Geotech Engineering and Testing. This paper also develops recommendations on how to better conduct geotechnical exploration for custom residential projects in the Houston area. Report Research In order to develop a State of Practice Report, research was conducted to find geotechnical reports for custom homes conducted by various Geotechnical firms in the Houston area. A total of 99 reports were located from GET's library and from various structural engineers throughout the Houston area. These reports were used as a basis of development of our findings. A map showing where these various soils reports for custom homes were conducted is shown on the site plan, Plate 1 of this paper. As indicated on this map, the concentration of these reports are located within 610 Loop area, near West University, Bellaire, Medical Center, and Kirby area. Furthermore, some of these reports are located along Memorial Drive, Hunters Creek Village, Piney Point Village and Bunker Hill area. A few data points are located outside the Loop. Principal Engineer,Geotech Engineering and Testing,800 Victoria Drive,Houston,Texas 77022,713-699-4000 2 Chief Engineer,Geotech Engineering and Testing,800 Victoria Drive,Houston,Texas 77022,713-699-4000 1 of 11 • Definitions The data developed during this research study are summarized on Plate 2 of this paper. The definition of each term used in this paper is presented below: Map I.D. - The map I.D. indicates where a specific soils report was conducted. The map I.D. is key to the site plan, Plate 1. Year - This indicates the year the soils report was conducted. Company - This term identifies which company did the soils report. We have companies A, B, C, .D, EF, G, H, J, K, L, M, N, O, P, Q, and R, a total of17. Report No. - This terns designates the report number for each specific company. Expansive Soils - This term signifies whether or not expansive soils are present at the job site. Expansive soils should have minimum plasticity index of 20 (Ref. 1). Trees on Site/Site Conditions - This term signifies whether or not trees were present on the site or the firm who conducted the geotechni.cal report had a Site Condition Section in the report. Sometimes, these soils reports did not even discuss the site conditions. In this case, a. dashed line is put in this space for the segment "trees on site/site conditions". Effective Plasticity index (PI) - This column presents the effective plasticity index of the soils developed by BRAB method (Ref. 2). Discussion of Expansive Soils - This column signifies whether or not the geotechnical report discussed the presence of expansive soils on the site. Discussion of Risks - This column describes whether or not the geotechnical report discussed various risks that are associated with different types of foundations used for residential foundations built on expansive soils. For example, a structural slab with void would be low risk foundation. However, a slab-on-fill pier foundation will have a higher risk than a structural slab with void type foundation system. A discussion of foundations and risk is given on Plate 3. Heave Computations - Most of the heave computations for residential projects (if computed at all) were computed by using Potential Vertical Rise method (Ref. 3). This column signifies whether or not a heave computation was computed for the soils report. 2ofII I r Drilled Footing Depth - This column signifies what was the recommended pier depth for the specific soils report. Structural Slab - This column signifies whether or not recommendations on a low risk foundation, which is a structural slab with voids/crawl space, was given in a specific geotechnical report. Furthermore, if recommendations on structural slab was given, whether or not recommendations on voids under the floor slabs was given. Therefore, this column signifies whether or not recommendations on structural slabs were present and if recommendations on structural slab were present what was the recommended void size under the floor slab (not under the grade beams). Slab-on-Fill - This column defines whether or not recommendations on slab-on-fill were given in the specific geotechnical report. Furthermore, whether or not a specific fill thickness was given. Some reports presented a very vague fill thickness recommendations. Void Box - This column signifies whether or not recommendations on void boxes were given under the grade beams. Drainage - This column signifies whether or not recommendations on site drainage around the house were given. Sprinkler - This column signifies whether or not recommendations on the presence of a sprinkler system, and their location around the house were given. Trees - This column signifies whether or not recommendations were given on planting a tree next to the foundation. Furthermore, it indicates whether or not recommendations were given on the existing trees next to the foundation. Tree Root Removal - This column signifies whether or not the specific geotechnical report discussed how to treat the tree removal from a specific site. What would be the ramifications of tree removal (heave). Construction Monitoring - This column signifies whether or not the geotechnical report gave specific recommendations on quality control such as conducting of testing including drilled footing observations, concrete testing, earthwork testing by the design geotechnical engineer. Review of Foundation Drawings - This column signifies whether or not the geotechnical engineer of record required that for the foundation drawings be reviewed by him/her to make sure his/her design recommendations are properly interpreted by the structural engineer anti other design team members. 3of11 Soil Variability - This column indicates whether or not the geotechnical report indicated that the soils across the site could be variable (from a standpoint of stratigraphy or properties) and there might be a need for design modifications if different soil conditions were encountered. Analysis of the Data General. The contents of all of these reports were reviewed and analyzed. The specific recommendations on analysis are presented in the following sections. Expansive Soils. Many of the reports acknowledged that expansive soils were present on the site. In general when the effective soil plasticity index is above 20, expansive soils are present on the site. 'frees on Site/Site Conditions. About 64% of the reports did not discuss site conditions. Specifically, they did not discuss whether or not trees were on the site or any other site features were located on the property. This is an extremely important part of a geotechnical report where many firms failed to discuss. Effective Plasticity Index. About 82% of the reports discussed how expansive the soils were at the specific site and gave plasticity index data in the report. About 91% of the sites reviewed had expansive soils on them. Discussion of Expansive Soils. About 82% of the soils report reviewed did have a discussion of expansive soils within the body of the report. Discussion of Risks. About 40% of the reports did not have a discussion on risks of using different types foundations. For example, they did not discuss whether a structural slab was better than a slab-on-fill type foundation supported on piers. Again, this is extremely important because, by discussing the risk associated with each different type of foundation, the soils engineer brings in the architect, the structural engineer, the builder and the owner into the decision making process. Heave Computations. About 74% of the reports did not discuss or calculate the heave. It is not customary to estimate the heave for design of custom residential foundations in the Houston area. One of the reasons for that is, it's not a consensus on the correct method for estimation of heave. Furthermore, it could be expensive. Therefore, most geotechnical consultants use their experience in specifying how much fill is required under the floor slabs to reduce heave on various types of residential foundations. The required fill thickness is usually determined based on the experience and engineering computations of the heave, such as Potential Vertical Rise, PVR (Ref.3). Drilled Footing Depth. An average pier depth of about 9-ft was specified after reviewing all of these reports. Review of reports from 1996 to 2001 indicated an average pier depth of 10.5-ft. Depth of drilled footings is very important in areas where expansive soils are present. Shallow piers can push up against the grade beams and lift the foundation system, if expansive soils are present at the site. The pier should be placed below the zero movement line. The zero movement line is a line below which no movement (heave) of expansive soils occurs due to weight of the colum of the soils. The piers should be anchored below the zero movement line. Currently, we recommend piers to be placed .12-ft to 15-ft in the Houston area where expansive soils are present. 4of1 Structural Slab Recommendations. About 55% of the reports discussed structural slab systems. The other 45% did not discuss it at all. Furthermore if they were discussed, most of them did not specify any kind of a void space that should go under the structural slab system. We believe that there should be a detailed discussion about the use of a structural slab. Furthermore, the recommended void size should he specified. In addition, recommendations on venting of the air underneath the slab should also be discussed. To limit moisture migration through the slab. This is only applicable to a structural slab with a void/crawl space. Slab-on-Fill. About 97% of the reports did specify a slab-on-fill type foundation or drilled footings system as the type of foundation that should be used to support the structural loads for a typical custom residential foundation. Some of these reports were vague, because they specifically say whether or not fill is required under the floor slabs. The vague statements given did not specify exactly how much fill should be placed under the floor slabs. Majority of the soils reports reviewed indicated the required fill thicknesses of about 24-inches or less. In general, a maximum of 48- inches of select structural till was specified in the areas where the soils were highly expansive. Our experience indicates that about four-ft of fill will generally reduce the movements to an acceptable level, provided positive environmental controls (drainage, trees, sewer/plumbing leak, etc.) are implemented. Void Boxes. About 38% of the reports specified the required void box size under the grade beams. Void boxes are recommended by many geotechnical firms in Houston as a way of reducing foundation movements. Expansive soils once swelled up can theoretically move into a void space area (void box) without lifting the grade beams. The discussion on whether or not void boxes should be used under grade beams on residential foundations was conducted by the Foundation Performance Association. It is generally believed that void boxes under grade beams provide channels for water to flow underneath the foundation system. Therefore, the use of them are discouraged. This discussion and idea was developed in 1996. Drainage. About 93% of the reports discussed that positive drainage was extremely important to the performance of the custom foundation system. Drainage was discussed in a majority of the reports. Sprinkler Systems. About 86% of the reports reviewed did not discuss the sprinkler system. They did not discuss how the sprinkler system (if used at all) should be placed around the structure to minimize moisture variations and therefore, differential movements. Trees. About 59% of the reports did discuss trees. Specifically, all the reports that discussed trees, described planting trees next to the foundation system and how they would affect the foundation system. It is understood that if the tree is left in place or planted next to a foundation system, it may cause the soil to shrink and the foundation to settle if clays are present. In all of the reports the word planted was synonymous with trees left in place. Tree Removal. About 70% of the reports did not discuss the tree root removal in their reports. This is an extremely important section of a report, because tree removal in areas where expansive soils are present, can cause significant heave. Therefore, the reports should address this condition and warn the client. This has not been customary in the Houston area until the year 1995. A detailed study of tree removal and its effect on foundation systems was presented in 1997 by Eastwood and Peverley (Ref. 4). 5of11 Construction Monitoring About 85% the reports suggested following up the design with construction monitoring. Construction monitoring is an important part of any design. Review of the Plans and Specifications. About 75% of the reports suggested review of the foundation drawings after the design was completed. The review of the foundation design drawings by the geotechnical engineer of*the record is important. This review will provide the client with the confidence that the initial designer (architect, structural engineer, owner) understood the soils report and followed the recommendations. It is possible once the drawings are reviewed by the geotechnical engineer of the record, mistakes are found that are reported to the structural engineer. Furthermore, foundation and risks are discussed. Soil Variability_ About 99% of the reports discussed the potential variation of soil stratigraphy and properties across the site. This is a true condition. Subsoils may vary across the lot from a standpoint of stratigraphy and soil properties. Conclusions and Recommendations Based on the review of the 99 reports written between 1990 and 2001 for custom homes in the Houston area, the following conclusions and recommendations can be made: o The soil reports reviewed from 17 companies represent a cross section of the geotechnical firms in the Houston area that do residential work for custom homes. o Many of these soils reports indicated the presence of'expansive soils in the vicinity of the project site. Most of them discussed the presence of expansive soils. o Only 36% of'the reports reviewed discussed site conditions. The rest of'the reports did not even address site conditions. The site conditions should be discussed in all reports. Perhaps a picture of the site should be included in the report. o Foundation types and risks must be discussed. o A review of' the reports indicates an average pier depth of about nine-ft. Pier depths have been increasing in depth in the Houston area since 1995. In the 1970's and early 80's, piers were placed at a depth of'about eight-ft. However, due to new understanding of the active zone depth and the effect of trees on foundations, deeper piers have been recommended. However, most geotechnical firms in Houston are not taking account the effect of tree removal in their foundation system. This condition was known to the Houston area after 1995 or 1996. Furthermore, the use of' deeper piers is resisted by some designers, builders, owners, etc., because this may add some to the cost of the construction of' the foundation system. However, we believe that increasing the depth of the piers by a few feet, the cost of the foundation system should not increase significantly. Furthermore, the risks of putting shallow piers in the area where expansive soils are present are too great. These shallow piers can actually be grabbed by the expansive soils and be pushed against the foundation system, resulting in floor slab heave. Considering that most of the distress of the newly constructed foundations in Houston is heave, the piers should be deep enough to resist uplift due to expansive soils. 6 of 11 o Almost all of the reports discussed the slab-on-fill on drilled footings. However, many of them did not suggest the required fill thickness. We believe that if this type of foundation system is recommended, the fill thickness should be clearly defined. Unfortunately, some soils reports are very vague about the required fill thickness. This has caused foundation problems, because inadequate fill thickness has been placed underneath the floor slabs. o About one-third of the reports did discuss the use of void boxes underneath the grade beams. Many of them did not. The use of void boxes is a controversial issue today. We do not recommend the use of void boxes under the grade beams. o Nearly all of the geotechnical reports discussed positive drainage as a major component of foundation design in their report. This should be covered in all reports. o Not very many reports discussed the presence of sprinkler systems around a house. We believe that the sprinkler system, if used, should be placed all around the house to provide uniform moisture conditions at the edge of the foundation. A non-uniform moisture condition will result in differential movement of the slab and foundation distress. o The area of the geotechnical reports that requires most improvement is the section that has to do with removal of existing trees. This issue must be further discussed in geotechnical reports. Currently, most geotechnical reports in Houston do not even discuss the effect of tree removal. In the event that a drilled footing foundation system is to be used, minimum boring depths should be 20-ft. Root fiber depth should be logged in the borings. Furthermore, the depth of active zone should be estimated. The effect of tree removal should be clearly discussed in the report. o Structural engineers who are designing a custom home must make sure the effects of tree removal have been considered in the geotechnical report prior to conducting a design of a residential slab. Some structural engineers blindly disregard this issue and they claim, they followed an erroneous soil report. Knowing the site conditions is also the responsibility of the structural engineer of the record. o None of the reports reviewed had any suction data or used suction to estimate heave. o The authors hope that in the future, the concepts, such as the use of suction will be implemented in the design of lightly loaded structures. Currently, most firms in the Houston area do not run suction tests on their soils samples due to costs associated with conducting this type of test and analyzing the data. Due to the extremely competitive nature of doing residential geotechnical work, it is almost impossible to do a detail geotechnical exploration and testing for residential projects. We believe that by providing a minimum standard in conducting geotechnical explorations, more firms will be interested in conducting more advanced and up to date geotechnical explorations and therefore, saving the client from the risks and spending too much money during construction and repair. Having a minimum standard is the only way, we believe, that the practice of design of a custom foundation system for lightly loaded structure in. Houston can be improved. 7 of 11 References I, David Eastwood and Others "Methodology for Foundations on Expansive Clays" Published in December, 1980 Edition of ASCE Journal of Geotechnical Engineering Division. 2. Building Research Advisory Board, National Research Council, "Criteria for Selection and design of Residential Slabs on Grounds," National. Academy of Science Publication 1571, 1968. 3. "Method for Determining the Potential Vertical Rise, PVR," State Department of Highways and Public Transportation, Test Method Tex 124-E, Austin, Texas. 4, D. Eastwood and D. Peverley "Design of Foundations with Trees in Mind", presented before the ASCE, Texas Section, Spring Meeting in Houston, April 1997. 8 ofI 1 ri? 'r} �, t ■ I _ , _ _. ,. 'vl. - s _ Pr d I - - ..:. f ! .,. -- T..._ .�_.- p, fs �. F 1a B '.- a 1, .--.. 1 F 1 ie2ff'� {avaev�y i Ki A `_ I I R '`"'a r. ,r :. 'S Y . fir. 3:; —°' "' n„ rte' Mfr ¢¢ g 1 ewe i ..- ' N... �r '+. ; ) 1 r " }. $E 4 ia;r!: �[� ! it i '''E' . ... 4 { '� :.,,,, ` �', 4,40.----t7:, ` .F.4-.X . aeI r iRi -°..„, 4„, .i r L f M d I� _ /".'”7 — ,,.„ 1 J.,. C. 4.R Y- .. ., } .,,, S? L®\ I 1 ..,47 . ! . .t,n,_ I s, ', 1 fit. 1 5,-_ r _ R �. ,- LI L.-: 111‘ I i 14 a1 '? ,4 3 n It > ' ! . a. I e al $ i t o f t#�j F` E ; �;, -1 � -_, ' Site Plan Plate 1 9of11 I STATE 432 PR2C GE,RESIDENTIAL FOUNDATIONS 1990 THROUGH 2001 I Egan Trees Effective Discussion Dlaulx Herne DR. Stec-8978`slxh �_ �Rnr;Tr. Ila0nns on Nan 1 Repo svo on Plastk. of n _ en- nn LX Box Root _ID_ "aur 1 Ton s, N.. Soils? � � 1 ('99101 Fsw1 n!1 Raxelnvrn Vold Ream/men- FI' I Cons, Review of Soil ___ Ftlpx PI tit. I Kisks Om De R N Ju!nnv I I----_—_ [fix Drain- S ler Root onilon Foundation f'tell I'Wien 1 19911 J 20390E Yes -. Sze.In tlYes flu kness,n •'a, I Yes leg lNo_ R No EtaYe.? Ufa Mk -e/ Nn No _ No N No Yes 12 �uv4 r Yes No No_ Nu Ye:' 2 •890 K 1 30.182; Yes - 0 Ves-- -'Yes I q Yes 4 I Yes _ .IA �� __ wo-sao_ YPa 49 Ye. Yea Yea a Yxa Yr. r9» ® Yen Yes -4._®`B e 91;1024 _Yes 1'xs 49 Ye, 1 Yes Na (19 Yes N—Yev f fl I� Y. �� 5 Ilzuela� H 222 I/ Yes - No iJn .E H G9i 5] _Yea 2.1_ __NC Nn _® Yxa ��_ IIn No ® N 601_5' Yes �e4; _Yes Yes 1q__ 1411_ II 191-1;, Yes_��1_ YP- I yn. 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Yes` Yes No 9 Yes � �® Y. ®®41 1493 ��®��� 9 ®�_ ��®� __ 03(540112 NISI®' WE No aINI® MIM��� ;535%/ WE= ® No ®�®®_ 3.3;3421 _� No ?__111111132111111111111 Ve ©MI® _� 4S 99 2 9311-1(121 11 Yes MEM �� 3 _� 4fi 053 B 3 ^719 �—M1//].����!}IY1J,��3j� J� 2]Ti 293E Yes A5 ©® � ii'J♦�L'i81 J 194.93E ��® Yas -A9 91 J- 1!A9.3E_������� No ��'-a� No ®��� 50 743 J 12/93E Nx- Nu ••�� 52 193 M MIM��n IIMM� 10 1I� Vo �' EI No' W_OM 3 I.)93 N 2'N0 2m—°�I�,�:mma,�aa ����,m��,�`®— 1993© ' 1,111 useiY✓•� mm �XUirn ��m®® 1Lx ® XM 7'c ®� 93-C,3, EaM � Mam� _ iimi 193 A 93 242E _ d��®�� m ® 1194 6 ®® �®®I���i 24 —®® 1=E1ks1� 59 '994 H C9`9 �° 3/ -_ _.. 1x9 17'.13 B 9404 OM - 90 1994 " 9404-1 OM Wi = 27 Y. - 18 4 1es 1, ®�X 31 �y ��11��® Yas ®� 18 3 `/es Il'ICi 63 I:YmJ4 7 94(®��1WYl/�®®___ �® Yaz ���, ��� - W ''994 4 0 ®_�_ ®Mill ��IUNN� =®N ®,994- ` �.'.s���®®©' �® 24 4 ���� ___ - 72 N4 E MUM �® _1a ��X�� ®0 11111=211121111112 6 ME11211.12.1.101.19• /1 I_J4 A 941 4E 4 5 �W� 3A � n—= /2 1935 E 95(515 E M ]:f 1995 B - 35;6]19 - - Yes 4 195© 96.68]6 ®®®®®®!�®� Yxa ®® /N 1905 F 95249-i �ES lli tstii�a�°�®®®�� ]6 ;955 r' 351184-1 ®® Y"_ 2i 1995 H__ ;95.221 Yes Yxs ® No Nu NO /3 11_15 F 9a,141n3 � n Nu Nn - ®®Vas 'ies Yxx _��NM_ (9!15 A I 9uACE Yes' Yes -_1 Vas -� _ __ • •Yec :AI 19<:f, t'-F-.G-11::9 _ © Ves lf. I d Yxs Von �� "Jo No U-3_ N Yes ...24 4 'to 19fi G96-205 Yes ® NO A =ME Yes N 1996 969351 Ya., ° - .. ® Yes 111131111111331•111131111121 ®�® Yxe a ®�� Yees ��®®®�� 96 49.713,.. Yes s t2 ®® , �� p No 1996 8 _ 9E93, Yes ® q vxs !' _14 _90 F,N 1!193 A 9t6*.'AE Yes II v ® - Yxs _ .- ® Nu 139/ E__ 3'/Gl01E ® _ Yes '6 Yes _ -_46 RR ;1,92 nl 27.%5133 Y. 40 I v 1a �� Yes aO w n ®® - _ Yes Yes 3 No - Yea A9 Irn]1 A 07118E Ye. - S2 y Ye- _ __ _ - _ vec Yea _— � � No IS Yes G Yes 48 Yes Yes �® yx-sza 9- 1993 A r2419E 'iaa_ Yna 50 YY. M _Nn Ifi '99235-1 Yxs Yes 31 Yes F R yea__ _ 2R _ ',PS o Yes El Yx_,_-. Jt,� _ Yes 9 Ye- Yes 24 el 2 ;71;1- 9/,G54-U Ys No 8S Y Pars No -U No �a No Yes ryu No 9t ..91 t I 9rIG,hMe Yes Yen <N V Yes No r!).- Yes __Yes 14 Yes No Yes Yon Nu-_ 90. 19.91 E , 99;5225 Yes No 41_ Yxa Yes _ Yes No Yea Yes__ Vxs Na l N No Y__ 24 Vas es Yes Yes En 95 1!199; _A___1 06.5(14E Y1n Yes_ Sn i Yx �NPe No I IU � Yas 5 f Yes d) — EMI OS 2009 1 G i no-I�t] Yes Yes Yes I No Yes Yes J] 2190 D 2Kt}I No V"' I I Yes - No No 1.o No Yes Yxs ITN -- _ Yes No i (0 _Yes d _Yes_ 13 No No No No Yes _ 96 2 0 A 00-8_225 Yen _Yes --195 Yes No Iti Y. - -- -'—' Yes_ 99 1 110, 91-009E You Yes 40 Yes _yes r YRs - 48 _ _ Yes 'Yes Y. Yes Yea Yes Yes _-_- No 1 ,E I 'Yes 3 11 Yes -+q Ver Yes Yea Yes Yes Yes 1'as NOT['I.Mi!;'c:1dIr10 recarYlenl{a4Uns oU hr_ave canVUlafiml and IiN thickness. -'—" � -� - �-_ � -' ''late 2 10o,`'II FOUNDATIONS AND RISKS Many lightly loaded foundations are designed and constructed on the basis of economics, risks, soil type, foundation shape and structural loading. Many times, due to economic considerations, higher risks are accepted in foundation design. Most of the time, the foundation types are selected by the owner/builder, etc. t should be noted that some levels of risk are associated with all types of foundations and there is no such thing as a zero risk foundation. All of these foundations must be stiffened in the areas where expansive soils are present and trees have been removed prior to construction. It should be noted that these foundations are not designed to resist soil and foundation movements as a result of sewer/plumbing leaks, excessive irrigation, poor drainage and water ponding near the foundation system. The followings are the foundation types typically used in the area with increasing levels of risk and decreasing levels of cost: FnLRJDATION TY"PF, REMARKS Structural Slab with Piers This type of foundation(which also includes a pier and beam foundation with a crawl space)is considered to be a low risk foundation if it is built and maintained with positive drainage and vegetation control. A minimum crawl space of six-inches or larger is required. Using this foundation,the floor slabs are not in contact with the subgrade soils. This type of foundation is particularly suited for the area where expansive soils are present and where trees have been removed prior to construction. The drilled footings must be placed below the potential. active zone to minimize potential drilled footing upheaval due to expansive clays. In the areas where non-expansive soils are present, spread footings can be used instead of drilled footings. Slab-On-Fill Foundation This•t.'oundati.on system is also suited for the area where expansive soils are present. This Supported on Piers system has some risks with respect to foundation distress and movements, where expansive sods are present. However, if positive drainage and vegetation control are provided, this type of foundation should perform satisfactorily. The fill thickness is evaluated such that once it is combined with environmental conditions(positive drainage, vegetation control)the potential vertical rise will he reduced. The structural loads can also be supported on spread footings if expansive soils are not present. Floating(Stiffened)Slab The risk on this type of foundation system can be reduced sizably if it is built and Supported on Piers. The Slab can maintained with positive drainage and vegetation control. Due to presence of piers,the either be Conventionally- slab cannot move down. However, if expansive soils are present,the slab may move Reinforced or Post-Tensioned up,behaving like a floating slab. In this case,the steel from the drilled piers should not be dowelled into the grade beams. The structural loads can also be supported on spread footings if expansive soils are not present. Floating Super-Structural Slab The risk on this type of foundation system can be reduced significantly if it is built and Foundation(Conventionally- maintained with positive drainage and vegetation control. No piers are used in this type Reinforced or Post-Tensioned of foundation. Many of the lightly-loaded structures in the state of Texas are built on this Slab) type of foundation and are performing satisfactorily. In the areas where trees have been removed prior to construction and where expansive clays exists,these foundations must be significantly stiffened to minimize the potential differential movements as a result of subsoil heave due to tree removal. The beauty of this foundation system is that as long as the grade beams penetrate a minimum of six-inches into the competent natural soils or properly compacted structural fill,no compaction of subgrade soils are required. The subgrade soils should;however, be firm enough to support the floor slab loads during construction. The structural engineer should design the floor slabs such that they can span in between the grade beams. 'the subsoils within which the grade beams are placed must have a minimum shear strength of 1000 psf and a minimum degree of compaction of 95 percent standard proctor density(ASTM D 698-91)at a moisture content within a2%optimum moisture content. Floating Slab Foundation The risk on this type of foundation can be reduced significantly if it is built and (Conventionally-Reinforced maintained with positive drainage and vegetation control. No piers are used in this type or Post-Tensioned Slab) of foundation. Many of the lightly-loaded structures in the state of Texas are built on this type of foundation and are performing satisfactorily. In the area where trees have been removed prior to construction and where expansive clays exists,these foundations must he significantly stiffened to minimize the potential differential movements as a result of subsoil heave due to tree removal. However,foundation tilt can still occur even if the foundation system is designed rigid. The above recommendations, with respect to the best foundation types and risks, are very general. The best type of foundation may vary as a function of structural loading and soil types. For example, in some cases, a floating slab foundation may perform better than a drilled footing type foundation. Plate 3 It of 11 FPA-SC-10-0 Quality Control Checklists for Foundation Inspection of Residential and Other Low-Rise Buildings 9 October 2003 For FPA Web Site Publishing Foundation Performance Association-Structural Committee Page 1 of 11 . QUALITY CONTROL CHECKLISTS FOR FOUNDATION INSPECTION OF RESIDENTIAL AND OTHER LOW-RISE BUILDINGS by The Structural Committee of The Foundation Performance Association www.foundation erformance.orc: Houston, Texas Document # FPA-SC-10-0 ISSUE HISTORY Rev# Date Description Subcommittee Subcommittee Chair Members A 02 Oct 01 For Subcommittee Comments __ Jack Spivey Ron Kelm B 19 Sep 02 For Subcommittee Comments Jon Monteith C 14 Oct 02 For Subcommittee Comments Michael Skoller D 26 Nov 02 For Subcommittee Comments Terry Taylor E 10 Dec 02 For Subcommittee Comments Mari Mes F 24 Jan 03 For Subcommittee Comments Mike Palmer G 06 Mar 03 For Subcommittee Comments Lowell Brumley H 28 Apr 03 Issued for Committee Comments George Wozny I 10 Jul 03 For FPA Peer Review Dan Daggers Toshi Nobe 0 09 Oct 03 FPA Web Site Publishing FPA-SC-10-0 Quality Control Checklists for Foundation Inspection of Residential and Other Low-Rise Buildings 9 October 2003 For FPA Web Site Publishing Foundation Performance Association-Structural Committee Page 2 of 11 PREFACE The following documents are the results of two years of work completed in the late nineteen nineties by the Inspections Subcommittee of the Foundation Performance Committee. Jack Spivey chaired this committee and his fellow members were: MR. MICHAEL SKOLLER P.E. MR. JOE EDWARDS MR.. LOWELL BRUMLEY P.E. MR. DEAN EICHELBERGER Meetings took place on a monthly basis and were attended by many interested parties. Special recognition should be given.to Mr. Jim Dutton of Du-West Foundation Repair and Mr. Dan Jaggers of Olshan Foundation Repair. Their assistance with the foundation repair sections was invaluable. The topics for discussion have followed a general outline, which was established at the onset of the meetings. It was determined that our basic intent would be to establish a set of standards and procedures for the inspection of foundation construction and foundation repairs. These standards were to be incorporated into an inspection document,which would be thorough in its scope, but also easy to use. It was established early on in our discussions that the best form for our purposes would be a simple checklist, which would fully cover the subject of the inspection. It was also determined that keeping the checklist to one page would afford the most user-friendly instrument for our purposes. Once these parameters were established the subjects of the inspections were taken in the following order: FOUNDATION MAKE-UP -- POST TENSION STRESSING POST TENSION FOUNDATION MAKE-UP -- CONVENTIONAL/REBAR CONCRETE PLACEMENT CONSTRUCTION PIERS REPAIR PIERS SEGMENTED REPAIR PILES These topics were judged to represent the major types of foundation construction and foundation repairs found in the Houston area. They are certainly not inclusive of every inspection situation or construction method in use, but they do offer a basic set of standards for the majority of inspections that would be encountered in typical residential construction. They are also designed to be used by anyone who has some knowledge of foundation construction. It was our intention that they would serve field inspectors,builders, builders' superintendents, municipal inspectors, or anyone with an interest in quality foundations. The first order of business worked on by the subcommittee was to establish a heading format for each inspection. This portion of the form is meant to establish a context for the inspection. The basics of the site such as, the builder, subdivision, address, lot and block, are all set out at the top of the form. The next section is meant to establish the parameters that will govern the rest of the inspection. The most important of these, deals with the plans. No inspection should be undertaken without a set of plans, which should include the name of the engineer, the date of the plans and the detail sheet. Other pertinent details of the site that are covered in this section are the date, the time, the weather, and whether there is a detached garage. FPA-SC-10-0 Quality Control Checklists for Foundation Inspection of Residential and Other Low-Rise Buildings 9 October 2003 For FPA Web Site Publishing Foundation Performance Association-Structural Committee Page 3 of 11 The above guidelines were followed on each form, with the following variations dictated by the context of the inspection: • For the Concrete Placement Form there is specific reference to the Foundation Make-Up Form,and the items in need of repair. • In the Stress Form, there is an added reference to the cable count, the concrete placement date, and the post tension construction company. • On the Construction Piers Form, there is a reference to the Geotechnical Engineer, and on the Repair Piers and Segmented Repair Piles Forms, there is reference to the design documentation and the municipal permit. Once the context is established in the heading, the foal'moves on to sections relating to different aspects of each inspection. In general, these sections are documented by simply checking the item to show that it has been correctly completed. The checkmark(✓)serves to show that the item has been considered and complies with the plans, whereas an x (x)denotes that the item does not comply with the plans. In some sections, direct questions are asked that should be answered. Finally, the lower sections of the forms generally have reference to a drawing of the slab, the piers or piles,or the foundation being repaired. The drawings further document the conditions specific to the site and the foundation and allow the inspector to orient the data being described in the conclusion of the inspection. Each of these forms represents an attempt to document the events related to a specific foundation project or a specific foundation repair. It should be remembered that all the answers and data reported are typically the only documentation of what actually happened during this phase of construction. For this reason, every item is pertinent and should be given careful consideration during the inspection. Though many of the items listed are fairly common knowledge to the typical inspector or builder, it is the sequencing and nuances of certain questions and items listed,which are the greatest advantage of using the forms. The committee felt that all major items such as beam size, tendon counts, plan dates, etc.,were adequately covered in each form. It should be noted that the Repair Piers and Segmented Repair Piles Forms contain information that is not found in any established sources or specifications. This is particularly true of the Segmented Repair Piles Form. It was generally agreed that these items are rarely inspected by an independent inspector. This document is made freely available to the public through the Foundation Performance Association at www.foundationperformance,org so engineers, architects, inspectors, contractors, and other professionals involved in the quality control of foundations systems for residential and low-rise buildings may have access to the information. To ensure the document remains as current as possible, it will be periodically updated under the same document number but with new revision numbers. Please direct suggestions for improvement to the current chair of the structural committee. The Foundation Perfotuzance 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-10-0 Quality Control Checklists for Foundation Inspection of Residential and Other Low-Rise Buildings 9 October 2003 For FPA Web Site Publishing Foundation Performance Association-Structural Committee Page 4 of 11 C.:4C CheckUsts 1. POST-TENSION SYSTEM FOUNDATION MAKE-UP 2. CONCRETE PLACEMENT 3, POST-TENS1ON SYSTEM STRESSING 4. CONVENTIONAL (REBAR) FOUNDATION MAKE-UP 5. CONSTRUCTION (BUILDERS) PIERS G. REPAIR PIERS 7. SEGMENTED REPAIR PILES FPA-SC-10-0 Quality Control Checklists for Foundation Inspection of Residential and Other Low-Rise Buildings 9 October 2003 For FPA Web Site Publishing Foundation Performance Association-Structural Committee Page 5 of 11 CLIENT QUALITY CONTROL COMPANY QC Checklist #1 - POST-TENSION SYSTEM FOUNDATION MAKE-UP— — —Builder Subdivision Date Time Site Address Lot Blk Sec Plan site specific Yes❑ No❑ Plan#: Cable Count__ Design Engineer Superintendent Plan provided at site Yes❑ No❑ Weather Plan Date Detail Sheet Date Concrete Contractor Detached Garage Yes❑ No❑ Permit#: Check(✓)If Items Comply With The Plans (X)If Items Do Not Comply With The Plans SITE FORMS ADDITIONAL REVIEWS Subdivision Lot _Other ❑Forms secure Date Time Lot Description ❑Floats installed Fill on site Yes❑No❑ ❑Proper clearance at floats Compaction verified by Geotechnical Engineer: ❑Garage front closed Yes❑No 0 Date Will foundation make up drain: Yes 0 No 0 Trees removed Are trees within 20'of foundation Yes Li No 0 SLAB TENDONS Thickness (in) Count: L to R F to B Garage Measured: Screeds Stringline___w Other_ Total Variance Explain Describe Pad Material Number of tendons left on site Rebar Level and Firm Yes No[] — 1/2"tendons_ Other —No tendons spaced over 6'-0" BEAMS —20D nails used at castings Design Depth: (in Exterior Interior i Live ends stripped of plastic not over 1"or taped Actual Depth: m (in) (in) (in) Cathead clamps all tight Design Width: in All intersections tied Actual Width: in (in) (in) m All tendons supported at intersections Average depth into undistur�ec�oil (in) Dead ends have 3/4"clearance to forms Clean of soil&debns All S Hooks crimped Water in beams Yes No Average Depth._ (in) Beam tendons draped and secured by#3 stakes or rebar concrete bricks Will water drain Yes No —Ample chairs all tied ❑Plumbing obstructions accommodated 'Tendon grid secured for concrete placement Yes 0 No❑ ❑Pier tops clean POLYETHYLENE SHEETING 6-mil.Lapped and Taped ❑Seated in bottom of beams secured at sides 0 Mastic/tape applied at plumbing REINFORCING STEEL SLAB SECTION WWF: Mesh)Size Roll Sheet OR ❑#3 @ in.)on center both ways All WWF(mesh)seams lapped 6" ❑#3 Lapped per plans 0 All edges 2"from forms No rebar or WWF(mesh)touching forms BEAM SECTION Rebar:grade— Clearances per plan: Sides❑ Bottom❑ Top❑ RS Corner rebar installed at corners&dead ends Typical Rebar/Exterior Beams continuous Typical Rebar/Interior Beams continuous Corner bars installed at dead ends Yes[_j No 0 Bay Windows or Porches Rebar Stirups Extra Rebar Added Diagonal Rebar at Re-entrant Corners ❑No.of Corners Nose Bars @ Construction Joints Anchor bolts on site Yes❑ No❑ Diameter (in)Length _(in) Other Fasteners Is FOUNDATION READY FOR CONCRETE? Yes 0 No 0 Sketch CHANGES NEEDED: Quality Controller's Signature Superintendent's Signature FPA-SC-10-0 Quality Control Checklists for Foundation Inspection of Residential and Other Low-Rise Buildings 9 October 2003 For FPA Web Site Publishing Foundation Performance Association-Structural Committee Page 6 of 11 CLIENT QUALITY CONTROL COMPANY I QC Checklist #2 - CONCRETE PLACEMENT Builder Subdivision Date Time Site Address Lot Blk Sec Plan#: Cable Count Design Engineer Superintendent Q.C.Arrival Time Departure Time Copy of Foundation Makeup Report Provided Yes❑ No❑ Date of Copy Items Repaired Yes❑ No❑ Concrete Contractor Detached Garage Yes❑ No❑ Permit#: Check V)If Items Comply With The Plans (X)If Items Do Not Comply With The Plans SITE FORMS ADDITIONAL REVIEWS Subdivision Lot Other 0 Forms secure Date_ Time Lot Description 0 Floats installed Are there obstructions at the site which would D Proper clearance at floats prevent access for concrete trucks Yes 0 No 0 0 Garage closed in Explain WEATHER —Weather conditions START: FINISH: Will temperature rise above 40°F for five hours Forty-eight hour forecast: HIGH TEMPERATURE: _ LOW TEMPERATURE: CONCRETE Concrete Company Batch Plant Tickets on site?Yes 0 No 0 Delivered by truck over what distance Was a pump used Yes 0 No 0 Pump Co. Mix: _ psi psi "pump mix"–Pump Prime Placed outside of form Yes 0 No 0 Sack Mix: 4 5 6 OR Strength Mix Yes 0 No 0 Strength Additives:_ NO CALCIUM CHLORIDE–APPLIES TO POST TENSION SLAB Fly Ash:Type C?Yes 0 No 0 Slump as ordered from plant (in) Explain(Discrepancies if slump is different): Was concrete consolidated by vibrator Yes 0 No 0 Other 0 Test Cylinders Taken Yes[]No 0 Testing Company Slump Test Taken Yes 0 No 0 Testing Company If water is added at the jobsite,show the amounts over ten gallons and give a visual estimate of the final slump Time Draw a diagram of the slab below showing the Poured Gallons Placement Est. Tested locations of each load by truck number Truck# Out Added Location Slump Slump Temp. Anchor bolts on site Yes 0 No 0 Diameter (in)Length (in) Other Fasteners SIM CH Describe provisions for curing ADDITIONAL COMMENTS: Quality Controller's Signature Superintendent's Signature FPA-SC-10-g Quality Control Checklists for Foundation Inspection of Residential and Other Low-Rise Buildin s For FPA Web Site Publishing Foundation Performance Association-Structural Committee 9 9 O Page 7 o of Pgf 11 CLIENT _ - QUALITY CONTROL COMPANY I QC Checklist #3 — POST-TENSION STRESSING Builder Subdivision j Site Address Lot Blk Date Time Plan#: Cable Count Sec Plan site specific Yes❑ No❑ Plan provided at site Yes❑ No❑ Weather Engineer Detail Sheet Date Placement Date Plan Date Detail.Sheet Date Stress Date Partial Stress Date Post Tension Company Permit#: Check(✓)If Items Comply With The Plans (X)If Items Do Not Comply With The Plans ❑Are there any cracks in the surface of the slab Yes❑ No❑ Describe —_-- — ADDITIONAL REVIEWS Dale Time Estimate size and locate on the sketch below ❑Are elongations specified on the plans Yes❑ No❑ ❑Are the tendons painted at the edge of the slab Yes❑ No❑ ❑What is the predetermined distance between the mark and the edge of the slab (in) ❑Are the wedges placed in a vertical position Yes❑ No ❑Is there evidence of gripper marks on the gripper end of all tendons Yes❑ No❑ (If no show location on sketch below) ❑Arc tendons stressed from two ends Yes❑ No❑ If So, How Many 112°' Diameter Tendon Elongation Measurements (Min/Max Range Recommended by PTI) v 19 ONNINIMMINIUMBIBEIMENNUteran Theoretical 9 +�fEEWII Minimum WIMIENNElinglaligiffillilltroMiffiliglii En 7 6 �� � M- 1 ®� .ii tC: 10 20 30 40 50 60 70 80 90 100 110 120 Tendon Length (ft) Out-to-Out of Concrete USE CHART IF ELONGATIONS ARE NOT LISTED ON PLAN,OR MULTIPLY TENDON LENGTH IN FEET BY 0.08 TO CALCULATE APPROXIMATE ELONGATION IN INCHES FOR LENGTH OVER 30 FEET. SKETCH Draw a simple sketch of the foundation configuration noting all tendon locations and their elongation measurements.Also note any problems which you have observed,particularly blowouts at corners or the FOLLOWING STRESS VERIFICATION garage entry and cracks. Li Are the tendon ends cut inside the pocket former ❑After stressing are the nails cut Are the tendon ends grouted with a non-shrink grout Quality Controller's Signature Superintendent's Signature FPA-SC-10-0 Quality Control Checklists for Foundation Inspection of Residential and Other Low-Rise Buildings 2003 For FPA Web Site Publishing Foundation Performance Association-Structural Committee 9 9 O Page er 8 of 11 1 CLIENT -- QUAL F("CONTROL COMPANY r QC Checklist #4 NVEN° IS NAL (REBAR) FOUNDATION MAKE-UP I Builder Subdivision Site Address Lot Blk Date Time Plan#: Design Engineer Sec Plan site specific Yes[I No El Plan provided at site Yes❑ No❑ Weather Superintendent Concrete Placement Date Plan Date Detail Sheet Date Detached Garage Yes❑ No❑ Permit# Check(✓)If Items Comply With The Plans (X)If Items Do Not Comply With The Plans SITE Subdivision Lot Other FORMS ADDITIONAL REVIEWS Lot Description Forms secure Date Time Fill on site Yes L j No❑ Floats installed Compaction verified by Geotechnical Engineer: Proper clearance at floats Yes❑ to❑ Date Garage front closed Will make up drain: Yes❑No❑ Trees removed Are trees within 20'of foundation Yes•No • SLAB Thickness__,____ _ (in) BEAMS Measured: Screeds Stringline Other Design Depth: in Exterior Interior Describe Pad Material Actual Depth: in (in) (in) (in) Level and Firm Yes 0 No❑ Design Width: in Actual Width: in m Average depth into undisturbed soil (in) (in) Clean of loose soil&debris Water in beams No—Average Depth (in) Will water drain Yes No — Plumbing obstructions accommodated POLYETHYLENE SHEETING Pier tops clean Yes❑ No❑ ❑6-mil.Lapped and Taped ❑Seated in the bottom of beams secured at sides ❑Mastic/tape applied at plumbing CONSTRUCTION PIERS Number of piers Are pier tops clean of debris Yes❑ No 0 REINFORCING STEEL Grade of Steel BEAM SECTIONS Exterior Beams: Steel size Number top Bottom Interior Beams: Steel size Number top Stirrup size Spacing Extra Beam depth Yes No p Bottom Stirrup size Spacing �in� p ❑ ❑ Additional steel required Proper Clearance: Bottom (in)Sides (in)To Continuity: Splices lapped per plan Yes No ( ) p Yes 0 No System Rebar clean of mud and excessive rust Yes �Corner bars installed Yes❑ No❑ Void Boxes in bottom of beam Yes❑ No DII Height (in) Condition SLAB REINFORCING Mesh: Size Roll Sheet ®All mesh seams lapped 6" OR 8#3 Lappe in.)All edges 2"from ways No rebar or mesh touching forms Pp per plans All edges 2"from the forms Void Boxes Yes❑ No L Height (in)Poly covering void boxes Yes❑ No❑ ADDITIONAL REINFORCING Diagonals: Size Number in slab Fireplace pads: Size of steel Placement Bay windows: Size of steel Placement Other projections: Control joints Construction joints: Anchor bolts on site Yes❑ No❑ Diameter Other Fasteners _—__ _(in}Length—_ (in) IS THE FOUNDATION READY FOR CONCRETE PLACEMENT?Yes❑ No 0 CHANGES NEEDED: SKETCH Quality Co stmer t- 's Signature �_ --- Superintendent's Signature FPA-SC-10-0 Quality Control Checklists for Foundation Inspection For FPA Web Site Publishing Foundation Performance Association-Structural lCommittteeer Low-Rise Buildings 9 October of i Page 9of11 CLIENT QUALITY CONTROL COMPANY QC Checklist — CONSTRUCTION (BUILDER'S) PIERS Builder _Subdivision _ Site Address Lot Blk Date Time Plan#: Design Engineer Sec Plan site specific Yes❑ No❑ Plan provided at site Yes❑ No❑ Plan Dateperintendent Geotechnical Engineer na Weather at site Detail Sheet Date Concrete Contractor Geotechnical Report# THIS FORM NOT APPLICABLE FOR SLURRY PLACED PIERS} Check(•7 If Items Comply With The Plans SITE (X)If Items Do Not Comply With The Plans Subdivision Lot Other Explain_ ADDITIONAL REVIEWS n__ Fill on site Yes No Date Time Compaction verified by Geotechnical Engineer Yes❑No❑ Date_____ Trees removed Yes❑No Li Location: Are trees within 20'of foundation Yes❑No• PIERS Name of drilling company: Can drill equipment access all pier locations YesETNo -- Type of drilling apparatus:Truck Mounted Total number of piers: Bobcat: Other: PIER SIZES Bell Pier No. R Stirrups t Depth R hat Rebar eb (m) (in) (ft) Rnarna Total On) (in) (in) (ft) (in) (1n) (in) (f) -- (in) (in) (in) (ft) (in) (in) Sketch Typical Pier Describe the manner of measuring the bell sizes: Showing Depth Boring logs from Geotechnical report on site Yes❑No❑ (Bell checking tool required) Describe bearing strata: Pocket Penetrometer reading taken from au er cutting Yes • No• TSF Was water apparent in pier hole Yes❑No I] Depth " Action Taken Note ocations below Rebar placed per plan Yes❑No❑ Rebar grade Does rebar extend above pier top Yes No❑ How much above CONCRETE (in)Sleeved Yes[]No❑ Describe Will concrete truck be able to access site Yes❑No❑ Concrete company: Truck numbers: Was pump truck used Yes No Specified strength of concrete: psi Was concrete placed on the same day as the pier drilling Yes[]No Estimated time of completion__________ if not,explain: Draw a sketch of the structure indicating the pier placement SKETCH ARE THE PIER HOLES READY FOR CONCRETE PLACEMENT Yes❑ No Ej CHANGES NEEDED: Quality Controller's Signature Superintendent's Signature 1 FPA-SC-10-0 Quality Control Checklists for Foundation Inspection of Residential and Other Low.Rise Buildin s For FPA Web Site Publishing Foundation Performance Association-Structural Committee g 9 October 2003 Page 10 of 11 CLIENT QUALITY CONTROL COMPANY I QC Checklist # — REPAIR PIERS Owner Subdivision Site Ad Lot Blk Date Time Address_ Plan#d Design Engineer Sec Plan site specific Yes❑ No❑ Plan provided at site Yes❑ No❑ Plan Date Superintendent Geotechnical Engineer Weather at site Detail Sheet Date Permit# Geotechnical Report# Check(✓)If Items Comply With The Plans SITE (X)If Items Do Not Comply With The Plans Subdivision Lot Other Explain ADDITIONAL REVIEWS Soils Report on site Yes[]No[] Bearing Soils at what depth ft Date Time Test hole drilled to what depth ft ) Underground plumbing test Yes-No ( ) Bearing soils at ft Site obstructions to drilling,Describe: Water lines under slab Yes[]No h if Trees removed Yes❑Non] Location UNDERPINNING Name of repair contractor: Method of repair: Total number of piers: Interior Exterior PIER SIZES Bell Pier No. Rebar Stirrups ►i- 1 _._< , { • ar __fin) (in) (ft ' r , (in) (in) (ft) (in ) (in) (in) (ft) (in) (in) (in) (ft) (in) (in) (in) (ft) (in) (in) Sketch Typical Pier Describe the manner of measuring the bell sizes: Showing Depth Describe bearing strata: (Bell checking tool required) Pocket Penetrometer reading Yes No Was water apparent in pier hole Yes Na Depth TSF Ac Note Action locations below IJ P " Action Taken REINFORCING Rebar per plans Yes❑No❑ Rebar grade HELICAL PIERS Test hole depth (ft) Bearing Data Helix Size Bracket Style Pier Log Onsite Yes❑No❑ CONCRETE Shaft Diameter Will concrete truck be able to access site Yes 0 No Concrete com an Was pump truck used Yes❑No p Y Truck numbers: Batch Time Specified strength of concrete: psi Slump as delivered Onsite Time Was concrete placed on the same day as the pier was belled Yes❑No Water added Yes 0 No❑Amount Projected time of completion of concrete placement If not,explain:_ ESTIMATED MAXIMUM LIFT INCHES: TO BE GROUTED Yes❑No❑ Draw a sketch of the structure indicating the pier placement SKETCH RARE THE PIER HOLES READY FOR CONCRETE PLACEMENT Yes❑ No L] CHANGE'S NEEDED: Ouality Controller's Signature Superintendent's Signature FPA-SC-10-0 Quality Control Checklists for Foundation Inspection of Residential and Other Low-Rise Buildin s For FPA Web Site Publishing Foundation Performance Association-Structural Committee g 9 October of 11 Page 11 of 11 CT_ —_--- QUALITY CONTROL COMPANY LQC Checklist #7-SEGMENTED REPAIR PILES Builder Subdivision Site Address Lot Blk Sec — — Date Time __________________ Plan#: Design Engineer Plan site specific Yes No Yes Plan provided at site Yes No Superintendent Geotechnical Engineer C Plan Date _ Detail Sheet Date Weather at site Permit# Geotechnical Report# Check(✓)If Items Comply With The Plans SITE (X)If Items Do Not Comply With The Plans Subdivision Lot Other Explain ADDITIONAL REVIEWS Geotechnical Report on site Yes No Bearing Soils at w at depth— ft Date Time Test hole drilled to what depth (ft) Underground plumbing test Yes-17 No (ft) Bearing soils at (ft7} Site obstructions to drilling,Descn e: Water lines under slab Yes No Trees removed Yes❑No 0 Location Were builder's piers present Yes❑No❑ —_ UNDERPINNING Name of repair contractor: Piling system: Total number o pi es: Interior Extenor FIELD OBSERVATIONS (A) (B) (C) (D) (E) Distance From Observed Pile Size Segment Number of Pile Cap Pile Cap To T o of of Total Depth Measurement s u Pile Size T e g e Number 1C c Top From Top of Lift O�antity Pile C"an of filch at ups , (d) (in) (in) )d d) (in) (in) $ (in) (in) -- (ft) ) (d) (d) (in) (in) (d) (in) in (ft) (in) (ft) (in) Total number of pilings observed driven to eA x Beti n(C x D)+E=TOTAL DEPTH (m) Was pile log available at the site Yes❑No❑ E (Minimum five is recommended) xplain Were the piles shimmed immediately upon completion of being driven Yes❑ No l If no,explain_ Is the piling cap horizontal Yes❑ No❑If no,explain Were the piles driven without interruption Yes❑ No❑ If no,explain Were builders piers detached prior to jacking Yes❑ No❑ Were final shims determined to be tight Yes❑ No❑ What is the method of interlock Were interior piles installed Yes❑ No❑If so,were tunnels used Describe Was dewatering system used and maintained in excavating and tunnels Yes❑ No❑ Describe materials used in backfilling tunnels Describe method of protecting tunnel entrance from water intrusion__— _-__ Was jetting required to install piles Yes❑ No❑Explain ESTIMATED MAXIMUM LIFT INCHES: TO BE MUD PUMPED Yes Draw a sketch of the structure indicating the pile placement CHANGES CHANGES NEEDED: ------- ---- ---------- Quality Controller's Signature Superintendent's Signature 2/9/2004 3:51 PM FROM: Fax TO: 713 839 9920 PAGE: 001 OF 002 City of est University Place Residential ial Engineering Requirements General Requirements Any Registered Professional Engineer Licensed by the State of Texas as a Structural Engineer shall be allowed to register with the City of West University Place to do Engineering work in the City provided a prior registration has not been revoked for reasons listed in the section Revocation of Registration below. At the time of registration.an engineer must provide proof of current registration, proof of general liability insurance, and sign a statement acknowledging that he has read and understands the specific requirements of the City of West University Place regarding engineering related to residential structures. All Plans submitted for new construction of residences or remodeling of residences where the costs of the remodeling will be in excess of $100,000 and which will require structural modifications to the residence shall be reviewed and approved by an engineer registered with the City of West University Place. Specific Requirements Engineers shall provide a load analysis for the structure. This analysis shall show the loads from the roof through the supporting foundation of any structure. For analysis purposes minimum gravity loads shall be as follows: Roof: DL=l0psf Ceilings: DL=5psf Floors: DL=10psf LL=20psf LL=10psf LL=40psf Wind Loads shall be calculated for the following minimum conditions: Wind Speed: 90mph Importance factor: 1 Exposure: B The engineering firm which designed the structure shall visit the site and inspect the work during construction to confirm that the work is done in accordance with the plans provided. The general contractor's employees or subcontractors shall not perform this function for the engineer. At a minimum the engineer shall inspect the work done on site during the construction of any piers or footings and during the construction of any beams or slabs. At a minimum the engineer shall confirm the following: That the number and placement of any piers or other footings is correct or acceptable given conditions encountered On site. -That the size and depth of any piers or other footings is correct or acceptable given conditions encountered on site. That any under reams are of the proper diameter and are free Iran any debris or caving. 2/9/2004 3:51 PM FROM: Fax TO: 713 839 9920 PAGE: 002 OF 002 -that any steel placed in the foundation is of the proper size and is located appropriately and that it has sufficient support to prevent it from moving inappropriately when concrete is placed in the forms. -That any concrete beams are of the proper width and depth and that the forms for such beams are clear of any debris or caving. -That any slab is of the appropriate thickness. That the weather conditions are appropriate for the placement of any concrete. The engineer shall arrange to meet a City inspector on site to during his inspections or provide other independent verification of his site visits. When the engineer is satisfied that any foundation work has been completed in accordance with the design provided a letter to that effect shall be provided to the City of West University Place. Independent Review The City of West University Place should contract with at least two registered professional engineers to review structural plans submitted for permitting. The scope of this review should be to review the load analysis and basic design for reasonableness. If the reviewing engineer has any questions regarding the reasonableness or completeness of the load analysis or of the structural design he should either contact the design engineer directly to resolve any questions or reject the plans with a list of questions. The Development Services department would then contact the design engineer to resolve any questions. If it is the opinion of the reviewing engineer that the design engineer has not displayed basic competence or due diligence he should advise the City of West University appropriately. Revocation of Registration If a reviewing engineer advises the City that he does not believe a design engineer has displayed basic competence or due diligence of if a design engineer fails to comply with the Specific Requirements the design engineer should be given the option of paying a fine of $500 or having his registration revoked. A second offence should result in a $1,000 fine or revocation of registration. A third offence would result in a three year revocation of registration • FPA-SC-04-0 Recommended Practice for Geotechnical Explorations and Reports 11 April 2001 Issued for Website Publishing Foundation Performance Association—Structural Committee Page 1 of 9 RECOMMENDED PRACTICE FOR GEOTECHNICAL EXPLORATIONS AND REPORTS by The Structural Committee of The Foundation Performance Association Houston, Texas Document # FPA-SC-04-0 ISSUE HISTORY (Only includes issues outside the Structural Committee) Rev Date Description Subcommittee Subcommittee # Chair Members D 19 Jul 00 Issued for Comments to FPA Ron Kelm Jon Monteith Geotechnical Engineers George Wozny E 21 Aug 00 Issued for Comments to Local Michael Skoller Geotechnical Engineers Moyeen Hague H 4 Jan 01 Re-Issued for Comments to Local Geotechnical Engineers J 1 Mar 01 Issued for FPA Peer Review 0 11 Apr 01 issued for Website Publishing I FPA-SC-04-0 Recommended Practice for Geotechnical Ex lorations and Re P orts Issued for Website Publishing Foundation Performance Association—Structural Pagge e 2 o of tural Committee 11 f 9 9 PREFACE This document has been developed by a group of Structural Engineers in southeast Texas with the goal to attain the geotechnical information they believe is necessary to adequately perform their structural designs. Their need for this document has been prompted by a large number of residential and light commercial foundation problems, some of which have been the subject of litigation. As a result,this document has been prepared specifically for the Structural Engineers' use. However, it is made freely available to the public through the Foundation Performance Association at www.foundationperformance.org so others may have access to the information and may adapt it to their work as they see fit. To ensure the document remains as current as possible, it is intended to be periodically updated under the same document number but with new revision numbers. This document is a recommended practice only and is therefore intended to be neither comprehensive nor a substitute for engineering judgment or for local or standard codes and practices. The user should recognize that there is always the possibility this recommended practice might not be fully adaptable to the site being investigated and in those cases,the use of engineering judgment will be paramount. The intent of this document is to detail certain minimum requirements recommended for the geotechnical exploration and report, thereby ensuring that the Structural Engineer receives the information needed to perform an adequate foundation design. Thus, Geotechnical Engineers preparing proposals for a geotechnical exploration and report in accordance with this recommended practice must all follow certain minimum proposal requirements,which can help ensure a more uniform selection process during the procurement of their services. In requiring the use of this recommended practice,the participating Structural Engineers understand that the request for the information specified herein would most likely increase the cost of the geotechnical work, since there is no intent to delete any of the work currently being executed in the geotechnical industry. However, they should also realize that this additional cost is necessary in order for them to better understand the soil characteristics of the site on which they plan to design a foundation. When using this recommended practice, it is expected that the Client will provide a description of the foundations and structures proposed for the site. In addition,the Client should provide site plans that show the foundation outline(s), the foundation location(s), and the location and species of any trees that are planned to be removed and that have trunk diameters equal to or greater than 6 inches. If the lots are Wooded Lots, it is intended that the Client will provide a tree survey to the Geotechnical Engineer, showing the location, sizes, species and condition of the trees on each lot. The Client should not discount this requirement as something less than a necessity. Though not recognized locally to be a problem as recently as ten years ago, trees in this area are now known or at least suspected to be the main contributor in the majority of foundation problems in the local market. Therefore the recommendations addressing trees should not be taken lightly. • FPA-SC-04-0 Recommended Practice for Geotechnical Explorations and Reports Issued for Website Publishing P i 1 Page 3 of 9 A Foundation Performance Association-Structural Committee Page 3 of 9 This recommended practice addresses a geotechnical report prepared specifically for foundation design and construction. In new subdivisions, the type of geotechnical report that addresses the streets and utilities is not acceptable as a substitute for the work specified herein. Preferably,the borings for a new subdivision should be taken after the streets are cut and the lot's fill is compacted. If however, the geotechnical exploration is made before the streets are cut, then it is the intent of this recommended practice that a separate exploration will later be procured in order to verify the required density,moisture content, and Atterberg limits for the fill material. This recommended practice is written specifically for use in Houston and the general southeast area of Texas. Therefore, it should be used with caution if utilized elsewhere or if adapted for foundations other than those supporting residential or light commercial structures. The main purpose of this recommended practice is to bring certain minimum requirements together into one document for local Structural Engineers to use in part or in whole, as they see fit. It is not meant to imply that problems will not occur if geotechnical explorations and reports comply in part or in whole with this recommended practice. The Foundation Performance Association and its members make no warranty regarding the recommendations contained herein and will not be liable for any damages, including consequential damages resulting from the use of this document. DEFINITIONS For the purpose of this document, the following definitions apply: Builder—The general contractor responsible for performing the construction of the foundation, including the site work. Client—The person or company using this recommended practice in the procurement of the geotechnical exploration and report. Geotechnical Engineer—The engineer or engineering firm responsible for performing the geotechnical exploration and for providing a report of the results. Structural Engineer—The engineer or engineering firm responsible for performing the structural design of the foundation. Wooded Lot— A lot that contains at least one tree per thousand square feet(1 per 1000 SF) of lot area, with those trees having trunk diameters greater than or equal to 6 inches. Note that the trunk diameter measurement is intended to be made at approximately chest-height above the ground level. Although the proper term for tree stem diameter in arboriculture is "caliper", that term is purposely not used herein because it is sometimes confused with "circumference"when measuring trees. FPA-SC-04-0 Recommended Practice for Geotechnical Explorations and Reports 11 April 2001 Issued for Website Publishing Foundation Performance Association—Structural Committee Page 4 of 9 TABLE OF CONTENTS 1.0 MINIMUM CRITERIA 1.1 General 1.2 Site Exploration 1.2.1 Area Reconnaissance 1.2.2 Borings Quantities and Locations 1.2.3 Boring Depths 1.2.4 Sampling Frequency 1.2.5 Field Testing and Logging 1.3 Laboratory Testing 1.4 Reporting 2.0 SPECIAL REQUIREMENTS 2.1 Slab-on-Grade Design Parameters 2.2 Drii led Piers Design Parameters 2.3 Suspended Slab Design Parameters 2.4 Select Fill Parameters FPA-SC-04-0 Recommended Practice for Geotechnical Explorations and Reports 11 April 2001 Issued for Website Publishing Foundation Performance Association-Structural Committee Page 5 of 9 1.0 MINIMUM CRITERIA The following subsections outline the Geotechnical Engineer's minimum requirements in accordance with this recommended practice. 1.1 General The Geotechnical Engineer should provide the Structural Engineer and Builder with sufficient information to enable them to: (a) design a structural foundation that is appropriate for the site conditions and is capable of adequately supporting the given building design loads, (b)provide a safe foundation design that meets local code and professional standards, and(c)carry out the site work and foundation construction in a safe and efficient manner. The Geotechnical Engineer should advise the Client if any requirements herein are in direct conflict with local codes and professional standards. In addition, the Geotechnical Engineer should carry out the work and prepare the report with the assumption that the Structural Engineer will never actually see the site for which the foundation will be designed. 1.2 Site Exploration It is the Geotechnical Engineer's responsibility to investigate the site as required to comply with local codes,professional standards and the requirements of this recommended practice. In addition, the site exploration should include the following minimum criteria: 1.2.1 Area Reconnaissance The Geotechnical Engineer should check the area of the building site and the area surrounding the site for any anomalies such as streams,ponds, fill, dumps, existing above-grade structures, escarpments, slopes,poor draining areas, seeps, outcrops, large trees,tree stumps, erosion, structures, roadways,railways, areas that appear to be wetlands, or anything else that will help the Builder and Structural Engineer understand the prior and present land use of and around the site. Representative color photos of the site should be recorded at the time of the site exploration and should be included in the final report. Where possible, the photos should include portions of the properties adjacent to the site. All anomalies, including trees and tree stumps with trunks equal to or greater than 12 inches diameter should be located on the boring plan. On.Wooded Lots the Geotechnical Engineer should superimpose the data from the Client-supplied tree survey on his plans. 1.2.2 Boring Quantities and Locations a. For new residential subdivisions that are anticipated to have grade-supported foundations, at least one boring per 5 lots is recommended,but not less than one boring every two acres. b. For new residential subdivisions that are anticipated to have pier-supported foundations, at least one boring per lot is recommended. c. For individual residential lots or for properties with light-commercial buildings, one boring for every 2,500 square feet of building ground floor slab,but a minimum of two FPA-SC-04-0 Recommended Practice for Geotechnical Reports Explorations and Re Issued for Website Publishin P P 11 April 2001 9 Foundation Performance Association-Structural Committee Page 6 of 9 borings for the lot. The borings should be taken inside the projected building perimeter or as close as possible, if obstructions exist. d. For lots with predominately cohesive soils and with trees growing within 25 feet(even if Located on adjacent property) of the proposed foundation, one boring should be taken within 10 feet, or as close as possible, of the largest tree having a trunk size equal to or greater than 12 inches diameter, even if this dictates an additional boring for the lot. e. For additions of less than 1000 square feet, one boring is adequate, except that the boring should be taken within the proposed foundation area and the recommendations in Paragraph 1.2.2d are still applicable. 1.2.3 Boring Depths Boring depths below are measured from the grade existing at the time of the site exploration. a. The minimum depth of every boring should be 20 feet. However, if the upper 10 feet are predominately cohesionless, then the minimum depth may be reduced to 15 feet. b. On Wooded Lots, or lots containing one or more trees with trunks equal to or greater than 12 inches diameter, and if these lots contain predominantly cohesive soils, borings should be a minimum of 25 feet depth. c. For sloped lots, where the proposed foundation is to be situated at a height H above the toe of an embankment(or estimated toe if submerged), if the horizontal distance from the foundation to the toe is less than 4H,then the depth of borings recommended should be a minimum of 2H. 1.2.4 Sampling Frequency a. Undisturbed samples should be taken at a minimum of 1-ft, 2-ft, 4-ft, 6-ft, 8-ft, 10-ft, 12-ft, 16-ft, 20-ft depths, and thereafter at a maximum of 5-ft intervals. b. If fill is known to have been placed on the site, sampling frequency should be increased to one sample per foot in the fill regions. c. A sample should also be taken at the bottom of the borehole. 1.2.5 Field Testing and Logging a. Each sample should be visually classified and logged during retrieval. b. Existence and depth of roots should be noted. c. Hand penetrometer testing should be done and reported on all cohesive samples. d. Standard penetration testing should be done and reported on all cohesionless samples. e. After the borehole is complete,measurements of the free water surface should be made and logged at completion of the borehole, and then again upon completion of the sitework, with that time interval being reported. 1.3 Laboratory Testing The Geotechnical Engineer should perform sufficient laboratory testing to comply with the requirements of standard codes and local practices. However, the following laboratory testing is recommended as a minimum: FPA-SC-04-0 Recommended Practice for Geotechnical Explorations and Reports Issued for Website Publishing p 11 April 2001 f 9 g Foundation Performance Association-Structural Committee Page 7 of 9 a. Existence and depth of roots or root fibers should be observed and reported for each soil sample. b. Moisture contents should be performed on all samples retrieved. c. In cohesive soils, Atterberg testing should be performed on a minimum of one third of the samples retrieved, with emphasis towards the upper strata. Reports should include plastic limits, liquid limits, and plasticity indices. d. In cohesive soils, the percentage of clay(minus 2 microns) should be tested using a hydrometer. e. Cohesive samples at the recommended foundation bearing depths may be tested using the torvane testing device provided a baseline test is made using unconfined compression tests for comparison. f. For lots that have predominately cohesive soils,testing at each boring location should be done to determine soil suction. Soil suction tests should be conducted using the transistor psychrometer method, the filter paper method or other methods that give similarly reliable suction values. Where suction testing is recommended, it should be done at sample depths of 2-ft,4-ft, 6-ft, 8- ft, 10-ft, 12-ft, 16-ft and 20-ft, but may be terminated earlier at the depth of constant suction, if determined. 1.4 Reporting The Geotechnical Engineers may use their own standard reporting techniques. However, the final report should also contain the following where applicable: a. A statement confirming that the geotechnical exploration and report are in accordance with the requirements of this recommended practice. If any exceptions are taken,the report should note each exception and the reason for taking the exception. b. A general description of the site and surrounding properties, specifically addressing the anomalies as discussed in Paragraph 1.2.1. c. Color photos of the proposed building site and where possibie, adjacent properties. A minimum of two photos is recommended, but the total number of photos should at least be equal to the total number of borings. d. A plot plan showing the approximate location of borings, tree trunks equal to or greater than 12 inches diameter and all anomalies as described in Paragraph 1.2.1. In the case of trees,include species where known,the condition of the tree if not healthy(i.e., "dying,"or"dead") and show trunk diameters,measured at chest-height. If the site personnel are unable to identify the tree species,then an attempt should be made to classify them into categories that help the user to estimate the potential water usage of the tree. For example a tree could be classified as either a hardwood or pine. Alternatively, it could be classified either as a broadleaf or conifer. e. Boring logs that include all field and laboratory tests results,unless particular data is presented on other charts or tables. f Descriptions and classification of the materials encountered. g. Elevation of the water table, if encountered. If no water was encountered,the report should state that the holes were "dry". h. Provisions to mitigate the effects of expansive soils. i. Recommendations on earthwork stabilization requirements(including requirements for slope stability)needed to prepare the site before the foundation can be constructed. FPA-SC-04-0 Recommended Practice for Geotechnical Explorations and Reports Issued for Website Publishing Foundation Performance Association-Structural Committee P 11 April 2001 Page 8 of f 9 9 j. A discussion on foundation maintenance required in order to maintain the design. k. Combined(i.e., for the various borings)plots of moisture content profiles and plastic limit profiles vs. boring depths. 1. Plots or tables showing the percentage of clay in cohesive samples as determined from hydrometer testing. m. A discussion of the degree of saturation or desiccation of the site as compared to the estimated equilibrium moisture contents of the samples. This can be presented graphically depending on the method used(e.g., a graph of moisture content minus plastic limit vs. depth). n. Combined(i.e., for the various borings)plots of suction values vs. boring depths. o. Interpreted output from the suction testing including the moisture active depth, the movement active depth, the edge moisture variation distance and the probable vertical movement,both up and down, of the ground surface. p. Specific discussion of trees to be removed before construction and of trees that are to remain. after construction is complete, if known. 2.0 SPECIAL REQUIREMENTS In addition to the general minimum criteria discussed above, there are some specific requirements that may be applicable to the Geotechnical Engineer, depending on the Client's needs. These requirements are as follows: 2.1 Slab-On-Grade Design Parameters Regardless of the type of building foundation planned,if design recommendations are provided for slab-on-grade foundations,then the Geotechnical Engineer should provide recommendations as outlined in both(a) WRI's "Design of Slab-on-Ground Foundations,"latest edition and(b)PTI's "Design and Construction of Post-Tensioned Slabs-On-Ground," latest edition. 2.2 Drilled Piers Design Parameters If design recommendations are requested or made for drilled piers such as those recommended for slab-on-piers (at grade), suspended(structural)slabs, or structural floor-on-piers (i.e., with a crawl space)foundations, then the Geotechnical Engineer should provide recommendations for pier depth that takes into account possible upward and lateral movements as well as the normal downward movement due to gravity loads. Upward movement should be addressed if the soil is predominately cohesive. 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F" 0 „ o Ora 44Pt:411;1; 4;1:7 As". ott\‘ 4;#;t711°07 4" E :fw-Z‘\\\___ __ Agenda Item # 6 Attention BSC, Please bring to the March 4th, 2004 meeting, a copy of your packet on Old Stock Housing Draft Objective- To develop a City Policy that promotes,protects, enhances and perpetuates Old Stock Houses within the City of West University Place. Over the years, West University Place has established an image within the area that is depicted by tree lined streets, bungalow style houses on small to medium lots and a high quality of life. Propose regulations should consider: 1. That promote the continuance of Old Stock Houses that represents historical elements of this image. 2. Foster Civic pride in the look of the past, 3. Protect and enhance West University Places attractiveness as a place to live, 4. 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