Structure , Home Inspection Course and Exam , North America , Canada

7/28/2019 Structure , Home Inspection Course and Exam , North America , Canada

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Structure


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THE HOME REFERENCE BOOK

STRUCTURE

76

INTRODUCTION

1.0WhyBuildingsMove

GRAVITY What causes structures to

move? In a word, gravity.

Gravityisconstantlyworkingtogetthingsclosertotheground.

Strongstructuresresistgravity.

STRUCTURE Therearetwocommonwaysa

structuremaygiveintogravity.

FAILURES a)If it is sitting on something

thatisnotstrongenough,the

groundbelowitwillfail.Bet-

tertobuildonbedrockthan

quicksand.

b)Ifthestructureitselfisweak,

itwillnotsupporttheloadsimposedonit.Thetotalload

ismadeupofthefollowing

Deadloadtheweightofthestructureitself, Liveloadfurniture,people,wind,snow

andearthquakes.

WIND Windactsintermittentlyonstructures.Windforcescanpush,pullorliftbuildings.Buildings

mustbestrongenoughtoresistthelateralandupliftforcesofwindaswellasthedownward

forceofgravity.Hurricanesandtornadoesareextremewindconditions.Theseoftenresultin

mechanicaldamagecausedbyprojectiles.

The structure of a home is the skeleton, which includes the foundations and footings as well

as the floors, walls, and roof. Structures are judged by how well they are able to stand still.

Successful structures do not move; unsuccessful ones do, sometimes dramatically.

In this section we will describe the purpose of the structure, and then look at all the structural

elements. Where there are several types, we will briefly outline each. We will describe what the

components do, what can go wrong, and what that means to the home.


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STRUCTURE


EARTHQUAKES Earthquakesalsocreateforces,whichcancausestructuralfailures.Likewind,theseforcesare

ANDEROSION intermittentandvariableandcanpush,pullorliftbuildings.Erosionisaslowerformofearth

movement,butitcanhaveadevastatingeffectonstructuresaswell.

COMPONENT House components may fail because theywere poorlybuiltwith impropermaterials, or

FAILURES thematerialswerepoorly assembled.Rot,insects,reandmechanicaldamagecan causewell-builtstructurestofail.Rustcanattackmetalcomponents.

COMPRESSION Whatforcesaffectindividualstructuralcomponents?Thetwobasicforcesarecompression

ANDTENSION andtension.Amaterialisundercompressionwhenitisbeingpushedfrombothends.Amate-

rialisundertensionifitispulledon.Componentsincompressiontendtogetshorterorare

squashed.Componentsundertensiontendtogetlongerorarepulledapart.Manybuilding

componentsfeelacombinationofcompressionandtension.

Somebuildingmaterialsare good in compression,othersworkwell in tensionandsome

perform well inboth.A pile ofbricks is very good in compression; you can standon it.

However,itisverypoorintension.Achildcanpullthepileapart.Achain,ontheotherhand,

isverygoodintension.Youcanpullquitehardonbothendsandnothingwillgive,butthe

momentyoutrytopushonit,thechaincollapses.Itisnotverygoodincompression.

SHEARINGAND Differentmaterialsfailindifferentways.Shearingandbendingarecommonmodesoffailure.

BENDING Shearoccurswhenadjacentfacesofamaterialmoveinoppositedirections.Whenabeam

splits,orabrickcracks,itisbecauseofshear.

Bendingismovementwithoutshearing.Aplankspannedbetweentwochairswillbendifsome-

onestandsonit,particularlyiftheystandnearthemiddle.Theupperhalfoftheplankispushed

togetherundercompression;thebottomhalfgetsslightlylongerbecauseitisintension.

Buildingcomponentsthatfailbybendingaresaidtosagorbuckle.Somematerialscanbend

asignicantamountwithoutlosingtheirstrength.Brittlematerials,however,donotbend

muchbeforetheybreak.Ductilematerialsdo.Ceramictileisbrittle,ropeisductile.Someductilematerialsareelastic.Thismeanstheywillgobacktotheiroriginalshapeafterbeing

bent.Arubberballiselastic;anailisnot.


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DEFLECTION Deflectionisamildformof

bending. If structures deect

justalittle,peopledonotmind.

Building codes stipulate how

muchdeectionisacceptable.A

typicaloor joist, forexample,

isallowedtodeect1/360thof

itsspan.

MATERIAL What makes a good building

SELECTION material? Itshould begood at

resisting the forces of tension

and compression. It should be

cheap, easy toworkwith, light,

long lasting,water, rot and re

resistant,andstableunderdiffer-

enttemperatureandhumiditylevels.Noonematerialdoesitall.Thatiswhyhousesaremadeofmanymaterials.Woodisoneofthebettermaterialsforsmallbuildings.Itisrelativelygoodinboth

tensionandcompression.Steelisalsogoodinbothtensionandcompression.

Buildingmaterialsarechosenbasedoncost-effectiveness.Thegoalistoassembleastructure

thatwillperformwellforassmallacostaspossible.Thiscanleadtosomeverysmallmargins

ofsafetyand,ofcourse,somefailures.Asnewmaterialsaredeveloped,theyaretried;insome

cases,withgreatsuccess;inothercases,withverypoorresults.

Thestructureisbyfarthemostimportantpartofthehouse.Thesafetyandusabilityofthe

entirehomedependsonitsstructuralintegrity.Sincemanystructuralcomponentsareburied

belowgradeorbehindnishes,muchofthestructuralinspectionisdonebylookingforevi-

denceofmovement.Wherenomovementhasoccurred,imperfectionsmaygoundetected.Newinteriororexteriornishesandpatchingworkmayconcealimperfectionsovertheshort

term.Inthesecases,problemswillnotbeidentied.

REPAIRS Structuralrepairscanbeverycostly,andinsomecasestheproblemissoseverethatthebuild-

ingistorndown.Inmanycases,astructuralengineershouldbeconsultedbeforemaking

repairs.Anincompleteunderstandingofaproblemmayleadtoincorrectsolutionsandalife-

threateningsituation.

CHAPTER In this chapter well look at foundation congurations briey, then discuss the various

ORGANIZATION structurecomponentsoneatatime,startingwiththefootingsandnishingwiththeroof.


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2.0Confguration

Homesmayhaveabasement,acrawlspace,both,orneither.Manyhouseshavepartialbase-

mentsand/orpartialcrawlspaces.Thecongurationisdeterminedbyclimate,cost,regional

buildingpracticesandrestrictionsimposedbythebuildingsite.Inareaspronetohurricanesandooding,buildingsmaybebuiltonpostsorstiltstokeepthehomewellabovegrade.

2.1Basement

Wherefrostfootingsarerequired,atrenchisneededaroundthehouseperimeterforthe

footingandfoundationsystem.Sincethisexcavationisnecessary,itisnotmuchmoreexpen-

sivetodigabigholeandcreateabasement.Inwarmclimateswherefrostfootingsarenot

required,basementsarerare.

Thebelow-gradespaceisinexpensivetobuildoncetheholeisdug,andcanbeusedforany-

thingfromroughstoragetolivingspace.Basementscommonlycontainthemechanicaland

electricalsystemsandmayincludeaworkroomandlaundry(althoughthelaundryisupstairsinmanymodernhomes).Gameroomsandfamilyroomsareoftenlocatedinbasements,and

completeapartmentscanalsobebuiltbelowgrade.

Disadvantagesofbasementsincludethesusceptibilitytowaterleakageandlackofnatural

light.Windowsinbasementsareusuallysmallandhighonthewall,sincemostofthewallis

underground.Basementceilingsareoftenlow,andevenifthereisnowaterleakage,theycan

becoolanddamp.

2.2Crawlspace

Whereatrenchisdugforthefoundations,andtheearthunderthehouseoorisnotremoved,

acrawlspaceiscreated.Itmayhaveanearthoor,althoughaconcreteslabismoredesirable

forstorageandmoisturecontrol.Manymoderncodescallforcrawlspacestobe36 inches

highwhereaccessmustbegained,althoughmanyoldcrawlspacesareless.Someareentirely

inaccessible.Restrictedaccessmakesinspection,maintenanceandrepairmoredifcultand

expensive.

VENTING Crawlspacesareoftenignoredfor longperiods.Wheremoisturelevelsarehigh,structural

damage,duetorotandinsectactivity,cangounnoticed.Somebuildingstandardscallforone

squarefootofventingforevery500squarefeetofcrawlspacearea.Thisisrarelyprovided.

Wherethecrawlspaceisdry,thismaynotbeaproblem.


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2.3Slab-on-Grade

Inthistypeofconstruction,apouredconcreteoorrestsdirectlyontheground.Theconcrete

slab is at least three inches thick and may ormay not be reinforced with steel bars.

Immediatelybelowtheslab,amoisturebarrieristypically laidoveraboutsixinchesof

gravel.Inmodernconstruction,insulationisoftenprovidedbelowtheslab.Slabsaretypically

supportedbyfootingsandfoundations.

Thereareseveraltypesofslab-

on-grade construction, includ-

ingmonolithicslab,supported

slab,andoatingslab.Amono-

lithicslabisaconcreteoorand

foundation all poured as one.

Thiscanbethoughtofasaoor

slab that is thicker around the

edges.Asupportedslabisnotpoured

together with the founda-

tion, but it does rest on the

foundation. The footings and

foundation wall are installed

rst,withaledgeatthetopof

the foundation to support the

slab. Basement oor slabs are

oftensupportedslabs.

Theoatingslabisentirelyinde-pendentofthefoundation.The

foundation is poured or built

rst.Theslabisnotsupported

byorconnectedtothefounda-

tion.Thistypeofslabiscommon

ingarages.

From an inspection and main-

tenance standpoint, slab-on-

grade is more restrictive than

homes with basements or

crawlspaces because none ofthefoundationisaccessible.


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SYSTEMS Basementorcrawlspaceoorsareoftenleftasexposedconcrete.Problemswithwateror

CONCEALED insectinfestation,forexample,canbepickedupearly.Withslab-on-grade,theconcreteslab

isnormallycoveredbysubooringandnishooring.Problemscangoundetectedforsome

time.

Wheretheslabispoorqualityconcrete,toothin,ormissingthereinforcingbar,theoorispronetocrackingandshifting.Subsurfaceerosioncanalsoresultinslabfailure,ascanareas

excavatedforplumbingorheatingpipes.This leadstobroken,unevenoorsurfaceswith

morepointsofentryforwaterandinsects.Substantialshiftingcandamagetheplumbing,

heatingandelectricservicesburiedinorbelowtheslab.Expansivesoilscanheavetheslab,

resultinginsimilarproblems.

3.0Footings

Thefunctionoffootingsistotransmittheweightofthehousetothesoil,withoutallowing

thehousetosink.Footingsarelocatedbelowthefoundationwalls,orattheperimeterof

slabs,andbelowcolumnsorpiers.Thehorizontalsurfaceof thefootingis largerthanthe

foundation,sotheloadofthehousecanbespreadoutoverawidearea.Footingsaretypically

16to24incheswideandsixinchesto16inchesthick.Incoldclimates,footingscarrythehouse

loadsbelowthefrostline.Theheavierthebuildingandtheweakerthesoil,thelargerthe

footingshouldbe.

Footingsmaybeconcrete,brickorstone.Inmodernconstruction,mostfootingsarepoured

concrete,oftenreinforcedwithsteelbars.

FOOTINGTYPES Stripfootings(alsocalledspread

footings) run continuously be-

low foundationwalls, typically

around thebuilding perimeter.

Pad footings (also called spot

footings)aresmaller and typi-

callysupportcolumnsorpiers.

PIERAND Pier andgrade beam construc-

GRADEBEAM tioniscommoninareaswithex-

pansivesoils.Concretepiersare

poureddowntoadepthwhere

the soils are stable. Grade

beams,whichoftenformfoun-

dationwalls,spanbetweenthepiers. These grade beams are

oftenreinforcedconcrete.


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CommonProblemswithFootings

Whenthefootingsfail,theentirehousemoves.Thisisoftenaveryseriousproblem.Itis

almostalwaysexpensive,andsometimesimpossible,tocorrect.Sincethefootingsarelocated

belowthesoil,theycannotbeseen.Itisoftendifculttoknowwhytheyhavefailed.

Settlementisthemostcommonformoffailure,althoughheavingiscommonincoldclimates

duetofrostexpandingthesoilbelowfootings.

Sometimes footingsfail inone

area, and in most cases the

failure is notuniform, (i.e. the

building doesnot sink straight

downbutleans toone sideor

another).Often,onepartofthe

housewill pull away from the

rest. This leads to cracking of

interior and exterior wall sur-

faces.

SETTLEMENT Soils prone to compaction or

WEAKSOILS movementdonotsupportfoot-

ingswell.Thisincludesrecently

disturbedsoil.Forexample,ifan

excavation for a foundation is

dugtoodeep,thenbacklledtothecorrectdepth,thedisturbedsoilunderthefootingis

likelytocompactovertherstfewyears,resultinginbuildingsettlement.

SETTLEMENT This is not common on pro-

ABSENCEOF fessionally-built houses, but

FOOTINGS may occur in casual construc-

tionaswellasonporchesand

poorly built additions. Some

homeswerebuiltonmudsills

woodbeamslaidontheground

with walls built on top of the

beams. Thesemud sills are re-

placed with a foundation and

footing system as the sills rot,

heaveorsettle.

SETTLEMENT Thesemayerodeorweakensoil

UNDERGROUND below the footings, causing

STREAMS severebuildingsettlement.Itis,

ofcourse,verydifculttolocateandtraceundergroundstreams.Theyoftenowonlyat

certaintimesoftheyear.


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SETTLEMENT Settlementmaybetheresultofpoordesign,oranadditionalloadthathasbeenadded.

UNDERSIZED For example, when a second oor is added to a bungalow, the weight may cause the

FOOTINGS footingstosink.Theadditionalweightofamasonrychimneycanalsocauselocalizedfooting

failure.

SETTLEMENT Thefootingmustbestrongenoughnottobreakapartunderaload,andmustbeabletostand FOOTING uptocontinuousexposuretodampsoil.

DETERIORATION

SETTLEMENT Ifthebasementoorislowered,thereistheriskthatthefootingswillbebrokenoffonthe

UNDERMINED insideorwilllosetheirsupport.Evenifexcavationisnotdonebelowthefootingsbutdown

ORCUT tothebottomofthem,thelateralsupportforthefootingmaybelost,andthefootingand

FOOTINGS foundationwallmaymoveinward.

SETTLEMENT/ Whenabasementoorislowered,thefootingsshouldbeunderpinned(loweredand,insome

WALLFAILURE cases,enlarged).Alternatively,onlythecentralsectionofthebasementshouldbelowered,to

LOWERED avoiddisturbinganyofthesoilnearthefootings.Dependinguponhowmuchthebasement

BASEMENT oorislowered,therequiredclearancefromthefootingsvaries.Asoilsengineerisoften FLOORS consultedandaconcretecurb(alsocalledabenchfootingorDutchwall)maybeneeded

aroundtheinsideedgeofthefootingstoensuretheyarenotcompromised.Buildingsettle-

mentandfailureoffoundationwallsarebothriskswhenloweringbasementoors.

Oneofthedangersinloweringbasementoorsistheincreasedriskofbasementleakage.

Noticeinthefollowingillustrationshowthedrainagetileoutsideisnolongerinthecorrect

locationoncetheoorislowered.Itistoohightobeeffective.

Whenexcavationisdoneontheexterior,(e.g.foranadditionorswimmingpool)thefootings

canbedamagedorunderminedinasimilarfashion.


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SETTLEMENT Housesbuiltonorclosetoslopesmaybesubjecttofailuresasaresultofsoilmovingdown

LOTSLOPE theslope.Thismaybeaslowsteadyprocessorasuddeneventtriggeredbyheavyrainsfor

example.Thiscanbeextremelycostlytocorrect.

SETTLEMENT Houses builton slopinglotsmaybemoreproneto footing and foundation failures. The

CUTAND chancesofbuildingondisturbedsoilareincreasedonlotssuchasthese.Effortsmadetolevel FILLLOTS andterracethelotmayresultin

soilbeingcutoutofthehillto

form a level terraceunder the

backhalfofthehouse.Thissoil

isthenusedasllintheadja-

centareawhere thefront half

of the house is to stand. The

downhillhalfofthehousemay

bebuiltonllthatmaynotbe

wellcompactedormaynotbe

abletostayinplaceandsupportthehouse.

On sloping lots, large lateral

earth thrust and hydrostatic

pressurecanbebuiltupbythe

soilonthehighsideofthehome.

Waterrunningdowntheslopeisblockedbythebuildingandaccumulateshere.

Onthedownhillside,thefootingsmaynotbedeepenoughincoldclimates.Frostheavecan

resultwherethefootingsarelessthanfourfeetbelowgrade.Thesideofthehousewiththe

lowergradeoftenhasawalk-outbasement,andchancesofafootingbeingtooshalloware

greatesthere.

SETTLEMENT/ Someclaysoilsthatexpandandcontractsignicantlywithdifferentmoisturecontentsmay

HEAVING alsoresultinfailure.Theseexpansivesoilscanheaveoorsandfoundationswhentheyget

EXPANSIVESOILS wet.Whentheydry,theyshrinkandallowthebuildingtodrop.Thisisasignicantcauseof

housestructureproblemsinsomeareas.

Treerootscanaffect themoisturecontent of soils noticeably.Most soils have strengths

thatchangewithdifferentmoisturecontents.Someclaysoilstrengthschangedramatically.

Thesearepoorbuildingsoils.Siltsarealsopoorbuildingsoils,inmanycasesmuchweaker

thanclay.


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EXPANSIVE Whereexpansivesoilsarecommon,heavingsoilbelowtheslabcanpushtheslabupwards

SOILSAND atthecenterorattheperimeter,breakingtheconcreteanddamagingutilitylines.Where

SLAB-ON- thesesoilsarecommon,theslabsaresometimespost-tensioned.Thismeanstherearesteel

GRADEHOMES reinforcing cables laid within

theslabandprojectbeyondthe

slab edge. The cables are

tightened afterthe concrete is

poured to strengthen theslab,

helpingitresisttheforcesofthe

expansive soils. The slabs are

sometimesthickenedinplaces,

often with beams running in

both directions on the under-

sideoftheslab.Thesearecalled

ribbedfoundations.

The expansive soils below theslabareoftensaturatedduring

constructionbeforepouringthe

slabsothesoilswillbeamaxi-

mum height when the slab is

poured.

FROSTHEAVE Ifthefootingsandfoundationsarenotdeepenough,thegroundbelowthemmayfreeze.

FOOTINGSTOO Frozenground expands andmay pick upall orpart of the building. This can do serious

SHALLOW damage.

FROSTHEAVE Exteriorbasementstairwellsmaycompromisethefootingsincoldclimates.Inordertobe

OUTSIDE effective,thefootingsincoldclimatesmustbebelowthefrostlevel.Whenanexteriorbase- BASEMENT mentstairwellisadded,thestairwellopeningeffectivelylowerstheexteriorgradelevel,and

STAIRWELL alsolowersthedepthtowhichfrostcanpenetrate.Afterthestairwellisinplace,thefrostcan

goseveralfeetbelowthebottomofthestairwellopening.Thiscanleadtofrostheavingof

thefootingsandthefoundations.


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A properly added exterior stairwell will include deepened foundations, or a completely

insulatedapproach,topreventfrostpenetrationbelowthebuildingfootings.

IDENTIFYING Duringaninspection,theresultsoffootingfailurecanusuallybeseen.Itis,however,difcult

THEPROBLEM toknowwhetherthebuildingisstillmoving,andifso,atwhatrate.Itisoftennecessaryto

monitorthebuildingoveraperiodofmonthsorevenyears,toknowwhethertheproblemwill

warrantrepair.Manyfootingfailuresarenotsevereenoughtowarrantrepairs.

REPAIRS The usual corrective action is

UNDERPINNING to underpin the footings. This

meansdiggingunder theexist-

ing footing, and adding a new

footing wider and/or deeper

thantheoriginal.Thismayhave

tobedoneinsmallsectionson

strip footings sinceone cannot

excavateundertheentirehouse

atonetime.Usuallytwotofour

footsectionsaredoneatatime.

Thisisveryexpensivework.


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REPAIRSPILES Insomecases,wherethesoils

ANDHELICAL aremovingorarelikelytomove,

ANCHORS underpinning is not appropri-

ate. Piles driven deep into the

ground are an alternative, but

may not be cost-effective for

an existing building. Helical

anchorsaresometimesscrewed

into the soil to support failed

footings.

4.0Foundations

4.1General

Foundationstransmittheweightofthehousefromtheabove-gradewallsandoorsdown

tothefootings.Wherethereisabasementorcrawlspace,foundationsalsoresistthelateral

pressureof thesoil.Thefoundationactsasaretainingwall inthissense.In coldclimates,

foundationscarrytheweightofthehousebelowthefrostlinetopreventfrostheaving.

Typicalfoundationmaterialsarestone,brick,pouredconcrete,concreteblock,cinderblock,

insulatedconcreteforms,claytile,andwood.Mostofthesematerialsbehavesimilarly.Wood

foundationsaretheexception.


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COMMON Foundationsmaybecontinuouswalls(stemwalls),oftenmadeofconcrete,masonryblock

FOUNDATION orinsulatedconcreteforms(ICF).Foundationsmayalsobepierssupportedbypadfootings.

TYPES Whereoodingisarisk,homesmaybebuiltonpiersthatarewellabovegrade.Piersmaybe

belowgrade,andmaybeconnectedbygradebeams.

Wheresoilconditionsarepoor,thebuildingmayrestonpilesthataredrivenorturneddownintothegroundtosomedepthtoprovideadequatebearingstrengthtosupportthehome.

Twocommonfoundationarrangementsareillustratedbelow.

CommonProblemswithFoundations

CRACKS/ Foundationwallsmaycrack,bow,spallorshift.Cracksmaybeduetoshrinkage,settlementor

BOWING/ lateralforces.Somecracksareseriouswhileothersareinsignicant.Bowingisusuallythe

SPALLING resultoflateralforces.Spallingindicatespoorqualitymaterialsorchronicwaterproblems.

Someofthecausesoffoundationdefectsareoutlinedbelow.


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INADEQUATE Basement and crawlspace foundations are really retaining walls, holding back the soil

LATERALSUPPORT outside.Ifthefoundationsdonotprovideenoughlateralsupport,theywilldeectinwards.

This may be the result ofmechanical forces exerted duringback-lling; back-llingwith

frozensoil(coldclimatesonly);unusualfrostdevelopmentinthesoilimmediatelyoutsidethe

building (cold climatesonly); foundationwallsthatare toothin, tootall ordonothave

adequatereinforcement;orthehouseoorsystemdoesnotprovideadequatebracingforthe

topofthefoundationwall.Thislastproblemiscommononthehighsidewallonaslopinglot.

Bothmasonrywallsandpouredconcretewallscanfailifnotproperlybuilt.

INWARD Foundationwallsthatmoveinwardcanberepairedbytyingthembackfromtheoutside,

BOWING usingtiesandanchors.Alternatively,buttressescanbeprovidedontheinterior.Theseoften

areconcreteorconcreteblockstructuresbuiltagainstthebasementwalls.Steelbeamsare

sometimesused.Therearealsomodernstructuralfabricsthatcanbeappliedtostrengthenwalls.Anotherchoiceistobuildanewfoundationwallinsidetheold.Insomecasesthe

foundationisreplaced.

BOWING/ Mechanicaldamagecausedwhenbackllingduringconstructionforexample,cangenerally

CRACKS be repaired on a localized basis, although re-excavation is often necessary. Using heavy

MECHANICAL equipmentnexttothehome(tore-paveashareddriveway,forinstance)canalsoexerthigh

DAMAGE horizontalloadsandresultinbowingandcrackinginthefoundationsofoneorbothhouses.


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BOWING/ Theheightofsoiloutsideafoundationmayexertenoughforcetocausethefoundationto

CRACKS fail.Conventionalfoundationscantypicallytolerate3feetto71/2feetofsoilheightonthe

HEIGHTOF outside.Thestrengthofthefoundationisdeterminedbyitsmaterialconcreteorconcrete

BACKFILL blockforexample,thestrengthoftheconcrete,thethicknessofthewall,whetherthewallis

laterallysupportedatthetop,andwhetherthewallisreinforced.

BOWING/ Theforceexertedbylargetreerootsonthefoundationwallcanleadtodeectionofthe

CRACKSTREE foundations.Somesoiltypesshrinkconsiderablyastheydryout.Ifalargetreedrawswater

ROOTS fromsuchsoilsbelowafooting,

thefootingmaydropasthesoil

compacts.Inthiscase,thetree

damagesthehousewithoutac-tuallytouchingit.

Intheshortterm,treerootdam-

agecan bearrestedbycutting

down the treeand leavingthe

roots in place. Over the long

term,therootsmaybeexpected

torot,leadingtosoilsettlement,

resultant water leakage and,

in some cases, building settle-

ment.Therootsmayhavetobe

removed.

SPALLING/ Waterpenetrationcandeterioratethemortarinmasonryfoundations,reducingitsstrength

DETERIORATION andultimatelyallowingshiftingtooccur.Thisisusuallyaslow,long-termprocess.

WATER

PENETRATION


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SPALLING/ Waterrelatedproblemsandwalldeteriorationduetomoisturepenetrationcanbeminimized

DETERIORATION oreliminatedwithcontrolofsurfacewaterontheexterior.Goodexteriorgradingwithground

SURFACE slopingdownawayfromthebuildingisimportant.Properperformanceofguttersanddown-

WATER spoutsisequallyimportant.Allroofrun-offmustbedirectedintoadrainagesystemoronto

thegroundatleastsixfeetawayfromthebuilding.

SPALLING/ Wheregroundwateristheproblem(anundergroundstreamorhighwatertable),gradingand

DETERIORATION downspoutapproachesmaynotproveadequate.Drainagetilesand/ora sumpandpump,

GROUND areoftennecessary.Consultantsspecializinginsituationssuchastheseshouldbeengaged.

WATER SeeSection10intheInteriorchapter.

SPALLING/ Lowqualityconcretesubjected todamp soilsmay deteriorate,losingits strength.This is

DETERIORATION commoninpouredconcretefoundations,builtintheearly1900s.Theinteriororexteriorface

POORQUALITY oftheconcretemaycrumble(spall).Reducingmoisturepenetrationwillretardthisaction,but

CONCRETE ifthedamagehasprogressedtoapointwherethestructuralintegrityiscompromised,sections

ofthefoundationsmayhavetobecompletelyreplaced.Thisisanexpensiveundertaking.

SPALLING/ Somebricksaredesignedforusebelowgrade,butmanyarenot.Theuseofinappropriatebrick DETERIORATION willresultinashortenedfoundationlife.Ultimately,thebrickshavetobereplaced.

POORQUALITY

MASONRY

FOUNDATIONS Ifthefoundationwallsdonotextendwellabovegradelevel,thewallssittingontopofthem

TOOSHORT maybeexposedtodampsoilandrotordeteriorate.Foundationsshouldextendatleastfour

tosixinchesabovegradelevel.

CommonProblemsinColdClimates

FROSTHEAVE In coldclimates, if the foundationsare too shallow, frostmayheaveeven thebest-built TOOSHALLOW footingsandfoundations.Onslopedlots,thepossibilityofshallowfoundationsisgreateston

thelowside.Propertieswithbasementwalk-outsareoftenvulnerabletofreezingdamage.

FROSTHEAVE Conventionalcoldclimateconstructionassumesthehousewillbeheated.Anunheatedhouse

UNHEATED may have frost penetrating through the basement oor below the footings, leading to

HOUSES heaving.Thereisariskinvolvedinleavingahouseunheated.


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ADFREEZING Adfreezingisaphenomenon

wherebydampsoilontheout-

side of the building actually

freezes to thebuildingand as

the soil heaves, itwill lift the

toppartofthefoundationwall.

Horizontal cracks in founda-

tionwallsjustbelowgradeare

typical.

4.2WoodFoundations

Preservedwoodfoundationswereintroducedintheearly1960s.Severalthousandunitshave

beeninstalled.Lifeexpectanciesofthebelow-groundwoodareestimatedinthe50to100

year range, considerably less thanmany traditional building foundationmaterials. Some

manufacturersoffer60yearlimitedwarranties.

Thewoodischemicallytreated

to retard rot. Chemical treat-

mentforwoodusedinfounda-

tionsismoreintensivethanthat

typicallyusedinwoodfordecks,

fencing,etc.Thewoodfounda-

tions may rest on concrete orwood footings. With wood

foundations, special care must

be taken to ensure that the

foundation is able to perform

itsretainingwallfunction(ade-

quatelyresistinglateralforces).


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CommonProblemswithWoodFoundations

ROT/INSECT Rotandinsectdamagearethemajorenemiesofwoodfoundations.Woodfoundationsshould

DAMAGE notbeusedinareaspronetowood-destroyinginsectssuchastermites.

4.3PileFoundations

Pilesaresteel,woodorconcretecolumnsdrivenintothesoil.Theyareusedinweaksoilsand

mayextenddownthroughthepoorsoil,toreachasoilwithgoodbearingstrength.Pilesmay

dependonfrictionbetweenthe

sidesofthepileandthesoilfor

theirsupport.Theymayalsobe

point bearing at the bottom.

The building itself rests on

beamsorwallsthatstraddlethe

piles. Piles are expensive andoncethebuildingisup,thereis

often noway to know if piles

have been used and where.

Again,thepresenceorabsence

of building settlement is the

onlywaytodeterminehowsuc-

cessfultheapproachhasbeen.

PILESAND Insomeareas,garagesaretypicallyconstructedonpiles.Thepilessupportpouredconcrete

GRADEBEAMS gradebeamsforexample,whichinturn,supporttheoorandwallsystems.Thegarageooristhenpouredontheundisturbedsoil.

4.4PierFoundations

Wherecontinuousfoundationsarenotprovided,individualcolumnsorpiersmaybeusedto

supportabuilding.Thepiersshouldrestonafootingbelowthefrostlineincoldclimatesand

typicallythepiersupportsabeam.Thebeam,inturn,supportstheoor,wallandroofloads.

Piersarecommonlyfound inhouseswherethere isno basement ora partial basement.

A crawlspace often has a pier system supporting the structure above. Porches are also

commonlysupportedbypiers.


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Piersmaybestone,brick,con-

crete block, cinder block, or

wood. Most of these materi-

alsbehaveinasimilarfashion.

Wood, of course, is the most

vulnerable to rot and insect

damage. As a rule, wood/soil

contactisbestavoided.

Concrete piers are often used

with grade beams where ex-

pansivesoilsareanissue.

CommonProblemswithPiers

SETTLEMENT Pierproblemsareoftentheresultofinadequatefootings.Thiswillresultinsettlementofthe

INADEQUATE pierand,ofcourse,thebuildingabove.Ifthepierbaseisnotbelowthefrostlineinnorthern

FOOTINGS climates,frostheavingcanbeaproblem. Inboththesecases, thepiersusuallyhavetobe

rebuilt.Similarproblemscanresultinareaswithexpansivesoils.

OVERSPANNED Ifthepiershavetoogreataspanbetweenthem,thebeamsmaysagortheconcentrated

loadsmaycausethepierstosink.Addingpiersisthetypicalsolutionhere.

TOOSLENDER Ifthepiersaretooslenderorareoutofplumb,theymaynotbecapableofcarryingtheir

OROUTOF intendedloads.Diagonalwoodbracesareusedinsomeareastohelpholdpiersinplace.Piers

PLUMB thataredeterioratedasa resultofmoistureormechanicaldamageshouldbe repairedor

replacedasnecessary.Woodpierscanrot,beattackedbywood-boringinsects,reorbedamagedmechanically.

SKIRTING Preservedwoodperformsbetterthanmostspeciesofuntreatedwood.Wherepiersareused

inlieuofacontinuousfoundation,thespacebetweenthepiersusuallyhastobelledinto

preventsoilfromfallingintothebasementorcrawlspace.Inabove-gradesituations,skirting

keepsoutanimalsand,tosomeextent,rain,snowandcold.Skirtingmaybewood,masonry

orpouredconcrete,forexample.Wheretheskirtingisnotstructural,repairstodeteriorated

skirtingareoftendeferred.Woodskirtingoftendeteriorateswhereitcontactsthesoil.


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5.0Floors

Floorsprovidethebearingsurfaceforpeopleandfurniture.Theyalsotiethebuildingtogether,

addingrigidityandprovidingasurfaceforoorcoveringsaboveandceilingnishesbelow.

Wewilllookatoorcomponentsoneatatime.

5.1Sills

Woodsillsprovidealevel,continuouspadbetweenthefoundationtopandthebottomofthe

framingsystem.Thesillssecuretheoorsystemtothefoundation.

ANCHOREDTO Typically,theoorjoistsrestdirectlyonandaresecuredtothesill.Sillsshouldbeanchored

FOUNDATION tothefoundation.Thisisoftenaccomplishedusingboltsanchoredintothetopofthefounda-

tionwall,passingthroughthesillandsecuredwithawasherandnut.

Innew construction, the sill is

typicallyawoodframingmem-

ber(2x4or2x6)laidat.Inolder

construction it may be a sub-

stantialwoodbeam(e.g. 8x8).

Wood sills can support wood

framing members but should

not support brick or stone.

CommonProblemswithSills

CRUSHED Sills may be crushed as a result of concentrated loads. Steel posts built into wallswill

CONCENTRATED sometimescausethis.

LOADS

CRUSHED Ifthebeamsorjoistsaretooshort,andonlytheveryendrestsonthesill(lessthanoneinch,

INADEQUATE forexample),theconcentratedloadsmaycrushthesill. ENDBEARING

MOVEMENT Wherethesillsarenotsecuredtothefoundations,thereisdangerofthebuildingshifting

INADEQUATE duringhighwinds,whensignicantupwardsandlateralforcescanbegenerated.

ANCHORING


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ROT/INSECT Woodsillsclosetogradelevelaresubjecttorotandinsectattackbecausetheyarewetmuch

DAMAGE ofthetime.Soilistypicallydamp.Sillsmayrotandcrushundertheweightoftheframing

system.Thiswillweakenthestructure,allowingittosettleslightlyandbreaktheconnection

betweentheoorandfoundation.

5.2Beams

Beamscarryoorandwallloadshorizontallytothefoundations,walls,columnsorposts.

Beamsmaybewood(solid,built-uporengineered),plywoodorsteel.

CommonProblemswithBeams

SAG Undersizedoroverspannedbeamsmaysagorcrack.Thismayleadto failureoftheentire

OVERSPANNED framingsystem.Fortunately,thisrarelyhappens,andalmostneversuddenly.Overspanned

woodbeamscanusuallybeidentiedreadily,andpostscanbeaddedorthebeamcanbe

strengthened.

CRUSH/FALL Wheretheendbearingisinadequate,thebeamcancrushitselforitssupport.Thereisalso

ENDBEARING potentialforthebeamtoslipoffitssupport.Typically,threeinchesisconsideredaminimum

endbearingforbeamswhensupportedbymasonryorconcrete.

ROT/INSECT Woodbuildingcomponentsarevulnerabletorot,damage,insectattackandre.Rotand

DAMAGE insectdamagearecommonwherethereiswood/soilcontact.Beamsbelowgradeshould

have1/2inchclearancealongthesidesandattheendtoallowforaircirculation.


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DAMAGE/ Mechanicaldamagecanbedoneaccidentallyorintentionally.Woodbeamsthatarenotched,

NOTCHED/ cut or drilled are weakened. The location and size of the damage determines whether

DRILLED correctiveactionisnecessary.

TWISTING/ Rotationofwoodbeamsdueto

ROTATION warping or poor support isrelatively uncommon but can

lead to damage and ultimate

failure.

NAILINGAND Built-up wood beamsmay not

BUTTJOINTS beadequatelynailed.Normally,

nailsshouldbeprovidedindou-

blerows every 18 inchesalong

thebeam.Wherebuttjointsoc-

curinwoodbeams,theyshould

be located over the supports

or as follows: the butt joints

shouldbewithinsixinchesofthequarterpointofthespan.Forexample,ifthespanis12feet,

thejointshouldbewithinsixinchesofthethree-footmarkorthenine-footmarkofthespan;

(i.e.thejointsshouldbe2-1/2to3-1/2feetfromtheendsupports).

RUST Steelbeamsaresusceptibletorust,particularlyifthebasementisdamp.Steelshouldbe

paintedtopreventrust.Lateralsupportforsteelbeamsistypicallyprovidedbywoodstrap-

pingsecuredtothejoists.

LATERAL Lateralsupportforsteelbeamsistypicallyprovidedbywoodstrappingsecuredtothejoists.

SUPPORT Thereareseveralwaystoprovidelateralsupportforwoodbeams.Seetheillustrationbelow.


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SECURINGTO Steelbeamsmaybepoorlysecuredtoposts.Windupliftmaycausethebeamtoliftoffthe

POSTS post,orimpactmayshiftitsothatsupportisnolongeroffered.Thebeamandpostshouldbe

bolted,weldedorclippedtogeth-

er. In hurricane or earthquake

areas, additional fastening may

be necessary. Special straps are

usedtoaccomplishthis.

STRENGTH A visual inspection of a steel

beam cannot determine its

strengthbecauseitdependson

morethansize.Theshapeofthe

beam,thelengthandthickness

of both the anges and web,

andtheweightperlinearfoot,

all inuence beam strength.

Thecarboncontentofsteelalsoaffectsitsperformance.

STEELVERSUS Steelbeamscanbemuchstrongerthanwoodbeamsandaremoreresistanttorot,insectand

WOOD mechanical damage, but are more expensive, heavier, and more difcult to work with.

Engineeredwoodbeamscanbestrongerthansolidwood,yetarelight,easytoworkwithand

lessexpensivethansteel.Woodbeamscanbecutonsitemoreeasilythansteel.Steelbeams

shouldrestonsteelpostsormasonry.Woodbeamscanrestonwoodmembers.

FIRE Fireisaconcernwithbothwoodandsteelbeams.Interestingly,asteelbeamwillloseits

strengthmuchearlierinarethanawoodbeam,althoughawoodbeamburnsandasteel

beamdoesnot.Steellosesitsstrengthafterbeingexposedtotemperaturesof1000F.for

aboutfourminutes.Steelbeamssaglikespaghettiduringare,allowingbuildingstocollapsequickly.Woodburnsbutlosesitsstrengthmuchmoreslowly.

5.3PostsandColumns

Posts or columns (two names

for the same thing) carry the

load of the beam vertically

downtothefootings.Theymay

bebrick,concreteblock,poured

concrete,wood,orsteel.


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CommonProblemswithPostsandColumns

SPALLING/ Masonrypostsmaybedeterioratedasaresultofmoistureorpoormortar.Risingdampisa

MORTAR common problem with brick columns. This is characterized by deteriorated mortar and

DETERIORATION eforescence(whitesaltydeposits)onthebottomofthepost.Insomecases,thebrickitself

deteriorates(spalls).

OUTOFPLUMB Poststhatareoutofplumbloseagooddealoftheirstrength.Generallyspeaking,ifthe

columnisoutofplumbbyroughlyone-thirdofitsthickness,theremaybeconcernaboutits

integrity.

RUST Rustonsteelpostscanbeaconcern.Thisisoftenaseriousproblematthebottomofthepost

inachronicallyoodingbasement.Rustwillquicklyreducetheloadcarryingcapacityofa

steelpost.

ROT/INSECT Woodpostsarevulnerabletorotandinsectattack.Thisisespeciallytruewherethepost

DAMAGE penetratesthebasementoorslab.Correctiveactionoftenincludessimplycuttingoffthebottomofthepostandplacingitonaconcretepad.

FOOTING A sinking post isusuallythe resultof amissing or inadequately sizedfooting.Obviously,

MISSINGORTOO suitablefootingsshouldbeprovided.Everypostorcolumnshouldhaveafooting.Thesecant

SMALL typicallybeseenoncethehomeisbuilt.

UNDERSIZEDOR Columncollapseissomewhatunusualbutisnormallytheresultofanundersizedcolumnor

DAMAGED onethathassufferedmechanicaldamage.

NOTWELL Apostthatisnotwellsecuredtothebeamabovecanallowthehousetoshiftduringwind

SECUREDTO upliftforces.Thebeamshouldalsobesupportedlaterallytopreventitfrommovingsideways.

BEAM SeeSection5.2.


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5.4FloorJoistsandTrusses

Thefunctionoftheseframingmembersistocarryandtransferloadsfromtheoorstothe

foundations,beamsorbearingwalls.

5.4.1ConventionalWoodJoists:Joistsaretraditionaldimensionallumber,typically2x8,2x10,or2x12.Thesehorizontalmemberscanbe12to24inchesapart,although16inchesisthemost

common.Theyarelaidonedge

sothatthesubooringisnailed

tothetwo-inchside.Floorjoists

should extend at least 1-1/2

inches onto the foundation or

beamateitherend.

JOISTSTRENGTH The strength of a joist comes

largelyfromitsdepth.Doubling

ajoistbyputtinganotherofthe

samesizebesideitwilldoubleits resistance to bending.

Doubling the depth of a joist

increasesitsresistancetobend-

ingbyeighttimes!Forexample,

the equivalent strength (con-

sideringdeectiononly)oftwo

2x10s compared to four 2x8s

canbecomparedbymultiplying

thebasetimestheheightcubed.Itisinterestingthattwo2x10saremoreresistanttobending

thanfour2x8s.

Thedeectionof aoorand joistsysteminmodernconstructionmaybequitesurprising.

Manycodesallowaoortodeect1/360thofitslengthundernormalloadingifthereisa

nishedceilingbelow.Forexample,thefollowingsituationisacceptablebymanycodes:2x10

oorjoistsspaced16inchesoncenterspanabout15feet.Whentheroomisoccupiedwith

furnitureandpeople,thecenterpartoftheoorcanbe1/2inchlowerthantheooredges.

Thisiscompletelysafe,andtheoorisnotatriskoffailing.However,thismaynotbesatisfac-

torytosomehomeowners.Codesareaminimumstandard.Brittleoornishingmaterials

likeceramictilemaynottolerateaexlikethis.Morerigidoorsareoftenusedwherethe

ooringmaterialisbrittle.

SPRINGYOR Floors are often bouncy or springy when people walk across a room, but this is not

BOUNCYFLOORS necessarilyindicativeofproblems.Lightframingcausesthiscondition,andwhiletheoorcan

bestiffened,thisisrarelydone.


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CommonProblemswithConventionalWoodJoists

OVERSPANNED Floorjoiststhatareoverspanned(undersized)arepronetosagging.Theacceptablespanof

ajoistisdeterminedbytheloaditwillcarry,thespeciesandgradeoflumberused,thedepth

of the joist, and the spacing

between joists. Over spanning

canbereadilycorrectedbyadd-

ing joists, or adding a beam

belowthejoistsinmostcases.

The implication of over span-

ning is typically a noticeable

sag,andinsomecases,abouncy

oorsystem.

DAMAGE/ Mechanicaldamageto joists is

NOTCHED/ common. Joists are commonly DRILLED notched,drilledandcutthrough

toaccommodateheating,plum-

bing and electrical systems. In

somecases,joistsarecutaround

stairwells to improve head-

room.Somedamageistypical,

andthereareseveralguidelines

onacceptablelimits.Joistsaresometimesnotchedattheendtorestonabeamorfoundation

wall.Thiscanweakenthejoistconsiderably.Thejoistusuallycrackshorizontallyfromthetop

ofthenotchtowardsthemid-pointofthespan.

INADEQUATE Joistsmaybepronetocrushingattheendsand/orslippingoffthebeamorfoundationwhere

ENDBEARING thereislessthan1-1/2inchofendbearing.


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JOISTHANGER Metalbracketscalledjoisthangersareusedwherejoistscannotrestonasupport.Here,the

PROBLEM joistsarecradledinandnailedtothehangers,whichare securedto thesideofabeamor

header.Joisthangersmaybeundersizedorinadequatelynailed.

ROT/INSECT Rotandinsectscanattackanywoodcomponents.Joistendsclosetooutsidewallsarevulner-

DAMAGE able,especiallyiftheoutsidesoillevelisashighasthejoists.

SAG Mostoorsaredesignedtocarryliveloadsof30to40poundspersquarefoot(psf).Larger

CONCENTRATED loadscan lead tosaggingandultimately, failure.Specialconsiderationmaybeneededfor

LOADS pianos,waterbeds,aquariums,andoor-to-ceilingbookstorage,forexample.

SAGJOISTS Joists that see concentrated

BELOWWALLS loadsaremorepronetosagging.

Ajoistbelowanon-bearingwall

should be strengthened, often

bydoublingit.Joistsshouldnot

be used below load-bearing

walls. Beams or bearing walls

shouldbeusedhere.


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SAG/HUMP One of the problems often unfairly blamed on joists is caused by an offset bearing

OFFSETBEARING wall. Many houses have a beam or a bearing wall in the basement or crawlspace

WALLS supportingtherstoor.Thereisoftenabearingwallabove,supportingthesecondooror

roofstructure.Ideally,therstoorwallisdirectlyoverthebeamorwallbelow.Ifthewall

isoffsetenough(sometimes12inchesisenough),thejoistswillsagundertherstoor

wallabove.Thiswillleadtoalowspotintheoorwherethewallsitsandahumpinthe

oorabovethebeamorbearingwallbelow.Thissortofmovementisrarelydangerousbutit

doesmakesomepeopleuncomfortable.

5.4.2EngineeredWoodJoists:Engineeredjoistsmayhaveconventionallumbertopandbot-

tomplates,orthetopandbottomplates(anges)maybeLVLs(LaminatedVeneerLumber),

PSLs(ParallelStrandLumber),orLSLs(LaminatedStrandLumber).Websmaybeplywood,

orientedstrandboard(OSB)ormetal.

LVLs,PSLs,andLSLscanalsobeusedasjoists,beams,sills,lintels,columns,studs,rafters,etc.

Glulams(gluelaminatedlumber),madeupofconventionallumberpiecesgluedtogether,can

alsobeusedformanywoodstructuralmembers.

These systemshavemuch longer spans than conventional lumber, andare less prone to

shrinkageandwarpingproblemsthanconventionallumber.Therulesforengineeredwood

aredifferentthanforconventionaljoists,andsomeoftherulesarespecictoindividualman-

ufacturers.Asalways,ahomeinspectionisavisualevaluationofeldperformancerather

thanadesignanalysis.

ProblemsSpecifictoEngineeredWoodJoists

DAMAGE Mechanicaldamageiscommon.Joistsarenotched,drilledandevencutthroughtoaccommo-

dateheating,plumbingandelectricalsystems.Insomecases,joistsarecutaroundstairwells

toimproveheadroom.Holesmaybetoobigorinthewrongplace(manysystemshaveknock-

outsthatindicatewheretheholesmustbe).Split,notchedorcutangesmaybeaproblem.

ThetopandbottomangesofwoodI-joists(asengineeredwoodjoistsareoftencalled)and

trussesarecritical.Anyweakeningwillseriouslyaffectthestrengthofthesystem.

INADEQUATE Inadequateendbearingisaproblem.Moreendbearingthanconventionaljoistsisoften

ENDBEARING required.1-3/4inchesisacommonminimum.

JOISTHANGER Metalhangerscalledjoisthangersareusedwherejoistscannotrestonasupport.Here,the

PROBLEMS joistssitinthehangers,whicharesecuredtothesideofabeamorheader.Joisthangersmay

betooshort,toowide,thewrongtype,andmaynothaveenoughnailsormayhavethewrong

kindofnails.

RIMJOISTISSUES Properrimjoistmaterialmaynotbeused.Engineeredwoodmayrequire3/4-inchplywoodor

specialrimjoistmaterials.Rimsshouldnotbeconventionallumber.Inadequateloadtransfer

throughrimjoistsisacommonproblem.

SQUASHBLOCKS Blocking(squashblocksorwebstiffeners)maybemissingor incompletewherejoistsrest

MISSING/ onbeamsorwhereloadsfrombearingwallsabovearetransmitteddownthroughengineered

INCOMPLETE woodjoiststobeamsorsills.


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BRIDGING Inadequatebridging or load sharing canbe a problem.Different systemshave different

MISSING/ requirementsforbridging.

INEFFECTIVE

5.4.3FloorTrusses:Thetopandbottomhorizontalmembersarecalledchords.Theshorter

interiorpiecesarereferredtoaswebs.Theyaremadefromwood,steeland/orplywood.Trussescanspangreaterdistancesthanconventionalwoodjoists.Beamsandpostsorbear-

ingwallscanbeomittedorremovedwiththeuseofoortrusses.Thesesystemsalsoallow

heating,plumbingandelectricalsystemstorunthroughthetrusses,leavingmoreheadroom

below.Trussesdonotnormallyrequirebridgingorbracing.

Trussesaredeeperthanjoistsandcanrestrictheadroominsomecases.Asageneralguide,

thetrussdepthis1/12to1/20ofitsspan.Mosttrussesare10to18inchesdeep.

CommonProblemswithFloorTrusses

UPSIDEDOWN Many trusseshavea topanda bottom,andmust be installed inthecorrectorientation.Atrussinstalledupsidedownisconsiderablyweakened.

CUT Trussescannotbecutaroundopenings,thewayjoistscan.Conventionaljoistscanbeeldcut

toappropriatelengths.Atrusscannotbecut.Allodd-lengthtrussesmustbeengineered.Site

conditionsthatarenotforeseenorlastminuteplanchanges,canleadtowastedmoneyand

delays,whenworkingwithoortrusses.

SPAN Trussesmaybeoverspannedjustlikejoists.Theseengineeredsystemscanonlybeevaluated

intheeldbytheirperformance.Homeinspectorsdonotreviewthedesignofengineered

systemsliketrusses.

DAMAGE/ROT/ Woodoortrussesarevulnerabletomechanicalabuse,rotandinsects.

INSECTS

5.4.4HeadersandTrimmers:Headersandtrimmersstrengthenanopeningintheoorjoist

patternforastairwellorchimney.Also,basementwindowsoftenpreventoorjoistsfrom

restingonthefoundationwallsandtheseopeningsintheframingpatternmustbestrength-

ened.

Normally,joiststhatcannotrest

onawallorbeamaresecuredto

a header. A header is typically

madeof the samesize lumber

as the joists (e.g. 2x8s). The

header,whichrunsperpendicu-lartothejoists,carriestheload

fromtheshortjoists(tailjoists)

overtotrimmerjoists.Trimmer

joists are the joists on either

sideoftheopeningthatrunfull

length.


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POSTS Postscanbeprovidedatthecornersoftheopeningtocarryloadfromtheheaderdirectly

downtotheoor.Inthiscase,thetrimmerscouldremainsingle.Theheadercanalsobe

supportedwithabearingwallrunningundertheheader.

CommonProblemswithHeadersandTrimmers

UNDERSIZED/ Undersized trimmers and headers are common. It is also common to have the trimmer

NOTCHED notchedatthebottomofthestairwelltoimproveheadroom.This,ofcourse,weakensthe

arrangement.

POOR Theshort(tail)joistsmaybepoorlysecuredtotheheader.Joisthangers(metalbrackets)can

CONNECTION be used to re-secure these tail joists. Headersmay also be inadequately secured to the

trimmers.Again,joisthangerscanbeused.

ROT/INSECT Rotandinsectscanweakenthe

DAMAGE stairwellopeningframing.

5.4.5BridgingandBlocking(andStrapping): Bridging/blocking

preventthejoistsfromtwisting.

Diagonalbridgingisusually2x2

woodblocksormetalstrapping.

Solidblockingisthesamesizeas

the joists. To be effective, the

bridgingorblockingshouldbein

astraightlineandshouldextend

thefulllengthoftheoor.

Solidblockingisrequiredattheendsofjoists.Talljoistsrequire

bridging or blocking at least

everyeight feet.Moreblocking

may be needed where earth-

quakesarearisk.

5.4.6 Cantilevers: Floor joists

maybecantilevered(extended)

slightly beyond their supports.

Acommonexampleisabalcony.

This isoftendone onanupper

oor,wheresupportpostswould

beexpensiveandunsightly.The

principle is that since wood is

relativelystiff,ifpartofajoistis

wellsecuredatoneendandpart

way alongits length, the other

endcanbeunsupported.Rough-

ly1/6ofthejoistspanbetweensupportscanbeusuallybecantileveredsafelybeyondasupport.


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CommonProblemswithCantilevers

OVERSPANNED Wherethejoistsarecantileveredtoofar,thedeckorbalconywillbeweak.Thisisusually

detectablebythespringinessofthestructurewhenwalkingonit.Inseverecases,failureis

possible.Postsorbracescanbeaddedbelowthedeck.

WATER Since the joists penetrate the buildingwall, there is the possibility of leakage into the

PROBLEMS wallsordirectlyintothehomeattheconnectionpoints.Thejointsbetweenthejoistsand

thewallmustbekeptwellsealed.Thisisacommonspotforrottodevelop,attackingboththe

cantileveredjoistsandthewallstructure.

ROT/INSECT Cantileveredwoodstructuresaresusceptibletorotandinsectdamage.

DAMAGE

5.4.7 Steel Floor Framing: Structural framing elements are generally either C-shaped or

U-shapedsteelcomponents.C-shapedelementsaredesignedasload-bearingelements,such

asjoists,whiletheU-shapedpiecesaretracks,orchannels,designedtoholdtheload-bearing

componentsinplace.

Steelframingmembersarenormallyscrewedtogether,althoughtheymayalsobewelded.

Membersmaybescreweddirectlytoeachother,orclips(clipangles)maybeusedtojoin

memberstogether,withtheclipbeingscrewedtobothelements.Screwsarealsousedto

join wood framing, sheathing,

and drywall nished to steel

framing. Securing joists to

steelbeamsrequirestheuseof

clips andpowder-actuatedfas-

tenerguns.

BEARING Bearingstiffeners(webstiffen-

STIFFENERS ers) are requiredwhere a con-

centrated load, suchas a door

jamb,restsonaoorjoist.These

usually take the form of a

sectionofstudortrackmounted

vertically on either sideof the

joistbelowthepointload.Web

stiffeners are also required

wherethejoistrestsonaload

bearingbeamorwall.

HOLES/NOTCHES Steeloorjoistsusuallycomewithpre-punchedholesforplumbingandelectricalwiring,and

shouldbeinstalledsothattheseholesarealignedforeasyinstallationofthemechanicaland

electricalsystems.Thereare industry-speciedrequirementsforotherholes.Joistsshould

notbenotched.


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BRIDGING/ Floorjoistswilltwistandbounceunderloadifthetopsandbottomsarenotproperlybraced.

BLOCKING Thetopistypicallybracedbytheooring.Thebottomscanbebracedwithadrywallceiling

forexample.Wherethereisnoceiling,thejoistbottomsshouldbebracedevery12feet.This

canbeX-bracing,atstrapsalongtheundersidesand/orsolidblocking.

FRAMING Whenthejoistpatternisinterruptedbyopeningsforstairwellsandchimneysforexample,

AROUNDSTAIRS reinforcingwithheadersandtrimmersisrequired,inmuchthesamewayitisdonewithwood

ANDCHIMNEYS framing.

CommonProblemswithSteelFloorFraming

RUST/ Steelframingmembersincontactwithmoistureforaprolongedperiodoftimewillcorrode.

CORROSION Thismaybeanissueinbelow-gradeareasorbelowrooforplumbingleaks.

OVERSPANNED Thespanofasteeloorjoistdependsonitsheight,widthandthegaugeofsteelused.Whilethere

aregeneralguidelines,individualmanufacturershavespecicrequirements.

POOR Weakscrewconnectionscanbeanissuewithsteelframing.

CONNECTIONS

CONTACTWITH Steel reacts with copper plumbing for example, and should not be in contact with

OTHER dissimilar metals. Unless special consideration is given, steel framing should not be

MATERIALS embeddedinconcrete.

DETERIORATION

5.5Sub-ooring(AlsocalledFloorSheathing)

Sub-ooringtransmitstheliveloadsof thepeopleandfurnishingstotheoor joists.Sub-

ooringmaybecoveredwithanishooringmaterialormayserveasanishooringitself.

One-inchthickwoodboardswereusedassub-ooringuntilroughlythe1960s.Morerecently,

plywoodandwaferboardhavebeenused.Thinconcretesuboorsarelesscommon.


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CommonProblemswithSub-flooring

SPRINGYFLOORS Subooringthatistoothinwillbespringyandmayfailunderconcentratedloads(e.g.a

piano).Thisshouldbeoverlaidtoprovideastiffersuboor.

SQUEAKY Subooring not adequately secured to the oor joists may be squeaky. The weight of

FLOORS someonewalkingonaoorwilltemporarilypushthesuboordownontothejoist.When

thefootisremoved,thesuboorwillliftoffslightlyagain.Thenoiseisthenailssqueakingas

theyslideinandout,orpiecesofwoodrubbingagainsteachother.Solutionstothisnuisance

includere-nailing,screwingandgluingthesuboortothejoists.

WATERDAMAGE Waferboardsubooringcanbedamagedbyrelatively smallamountsofwater.Theboard

tendstoswell,resultinginoorunevenness.Theswellingalsopullsthenailsoutofthejoists

orthroughthewaferboard.Ultimately,theboardcanloseitsstrength.

EDGESUPPORT Diagonalplanksubooringmustbesupportedwhereitmeetsthewall.Theendsofsomeof

theplanksmaybeseveralinchesfromaoorjoistandifadequateblockingisnotprovided,the oor will be weak in this

area.Whereplywoodorwafer-

boardsubooringsheetsmeet,

thejointshouldbesupportedby

joists, blocking or tongue-and-

groove connections between

thesheets.

DAMAGE Any subooring can be me-

chanicallydamagedand,unless

repairsaremade,thiscanlead

toan unsafe situation. A com-

monproblemisaholecutfora

heatingregisterthatwasnever

installed. If carpet is laid, this

maynotbenoticeduntilafurni-

turelegisputontheweakspot.

Repairs are, of course, simple

andinexpensive.

UNEVEN Unevensubooringcanbeanuisance.Unevenjoistinstallationisacommoncause,asis

debrisonthetopofthejoistswhenthesuboorislaid.Swollenwaferboardordelaminated

plywoodcanalsoresultinunevenness.Carelessjoiningoftongue-and-groovesheetscanleadtosurfaceirregularity.

ROT/INSECT Subooringissusceptibletorotandinsectdamage.

DAMAGE


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5.6ConcreteFloors

Concreteoorsinhomeswithbasementsareusuallynotstructural.Basementandgarage

oorslabsrestonthegroundandareusuallypouredafterthehouseisbuilt.Modernoors

aretypicallythree-inchthickslabs,althougholdonesmaybeasthinas1/2inch.

Slab-on-gradehomesmayhaveconcreteoorsthatarepartofthestructure.

CommonProblemswithConcreteFloors

CRACKED/ Floorsmaybecrackedorbroken.Replacementisnotapriority,butisoftendonetomakea

BROKEN basementorgaragemoreusable.Brokenutilitylinesareapossibilitywithslabmovementon

slab-on-gradehomes.Themovementmaybesettlementorheavingduetoexpansivesoils,

forexample.

NOSLOPETO Manybasementandgarageslabsdonotslopetodrains.Re-slopingisrarelydonebecauseit

DRAIN isexpensiveandtheproblemofwateronaoorisrarelyserious.

SUSPENDED Suspendedconcreteoorsarenotcommoninhomes.Oneexceptionisconcreteporchslabs

SLABS abovecoldcellars.

Suspendedconcreteoorsabovegradearecommoninhigh-riseandcommercialbuildings,

andusesteelreinforcing.Theyareheavierandmoreexpensivethanconventionalwoodoors,

butcanalsobestrongerandaremorereresistant.Suspendedconcreteoorsystemsarenot

evaluatedduringahomeinspection.

6.0WallSystems

Wallscarrytheweightoftheroofandoorsdowntothefoundations,aswellasprovidingaseparationbetweeninsideandoutside.Wallskeepoutthewind,rain,heat,cold,andnoise,as

wellasprovidinguswithprivacyandsupportforinteriorandexteriornishes.

Afterahomeisbuilt,itmaybedifculttoidentifythewallconstruction.

6.1Materials

6.1.1MasonryWalls:Commonmaterialsincludebrick,stone,concreteblock,cinderblock,

claytileandglassblock.Masonrywallsaretypicallycomprisedoftwofour-inchthickwythes

(layers)of masonry. Theouterwythe isoftenweather-resistantbrickor stone. The inner

wythe(layer)maybelowerqualitybrick,concreteblockorcinderblock.Thefoundationmust

bewideenoughtocarrybothlayersofmasonry.

Mortarusedtobindmasonryunitstogetherisacombinationofcement,sand,andwater.For

moreinformationonbrickandmortar,seeSection3.2intheExteriorchapter.

Themasonryunitsmaybeexposedorcoveredwithstucco,forexample.


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IDENTIFICATION Inmostcases,asolidmasonrywallcanbeidentiedbytheheadercourses(rowswherethe

brickisturnedend-wisetolocktheinnerandouterwythesofthewalltogether).Thisisdone

everyvetosevencourses(rows)upthewall.Sometimeseverybrickinthecourseisturned

end-wise.Often,onlyeveryotherbrickisturned,andsometimesthepatternisrandom.In

mostcases,however,thereareatleastsomeoftheunitsthatareturnedineveryfth,sixth

orseventhcourse.

Metaltiesorspeciallysizedbrickscanalsobeusedtojointheinnerandouterwythes.In

thiscasethewallwillshownoheadercourses,anditwillnotbeapparentthatitisasolid

masonrywall.

Solidmasonrywallshavenotbeencommonlyusedon single-familyhomesinmanyareas

sincetheearly1970s.Areaspronetohurricanesareanexception.

CommonProblemswithMasonryWalls

DETERIORATED Thewallmaybeweakenedifthemasonryorthemortardeteriorates.Thismaybetheresult

ofpoorqualitymasonryormortar,chronicmoistureexposureorfreezing.

CRACKS Cracksinbrickworkmayappearforseveralreasons.Cracksareclues,andtheirsize,location,

directionand rate ofgrowth are all indicatorsofwhat ishappening.Generally speaking,

cracksthroughmortarjointsarelessseriousthancracksthroughthebrickorblock,butthere

areexceptions.


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LEAN/BOW Wheretheinnerandouterwythesarenotadequatelysecuredtogether,theouterwythescan

leanorbowoutwards.Theentirebrickwallmayleanorbowduetofoundationsettlementor

thewallnothavingadequatelateralsupport.Wallsmayalsobepushedoutofplumbby

vehicleimpact,forexample.Ifawallleans,theultimatedangeristhatitmayfall.Themore

immediatedanger,however,isthattheraftersandjoistsrestingonthewallmayslipoffas

thewallmovesoutawayfromthebuilding.Sincetheendsofjoistsmayonlyrestonthewall

byaninchortwo,alittlemovementcancreateanunsafesituation.Ifjoistsorraftersslipoff

theirsupports,theframingsystemwillcollapse.

RAFTERSPREAD Spreadingroofraftersmaypush

thetopofthewallsout,result-

inginanunstablesituation.


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EXCESS Brickcanbecorbelled (offset)

CORBELLING onlyaboutoneinchbeyondthe

brickbelow(i.e.onebrickdoes

nothavetobesetexactlyontop

ofanother).However,thetotal

corbellingmustnotexceedone-

third of the wall thickness to

maintainstability.

6.1.2WoodFrameWalls:Load-

bearingwoodframewallsmay

beinteriororexteriorwalls.

Some stud walls are load-

bearing,othersarenot.Bearing

wallsshouldhaveadoubletop

plate. Non-bearing stud walls

mayhaveonlyasingletopplate.

Asinglesoleplate(alsocalledsillplateorbottomplate)isprovidedineithercase.Noneofthis

isvisibleoncethehomeisnished.

Historically,2x4studshavebeenused,spaced16inchesoncenter,althoughmorerecently,

2x6exteriorwall studs have become common asthey providemorespace for insulation

betweenthestuds.


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CommonProblemswithWoodFrameWalls

Rot, insect attack, mechanical damage, poor quality lumber, poor connections, design

mistakes,poorworkmanshipandexcessivespacingcanallbeproblems.

POORNAILING Inadequatenailing can lead to

ANDOPENING difculties. Openings in walls

maynotbeadequatelyframed.

Wall sections above large

openings for picture windows,

for example, may sag if the

openingsare notbridgedwith

appropriate support headers

(somecalltheselintels).

NOTCHES Holesandnotchescanweaken

ANDHOLES studsiftheyaretoolarge.The

illustrations below provide

someguidelines.

BUCKLING Somewoodstudwallsaresusceptibletobucklingunderloads.Thisisparticularlytrueifthe

wallsarenotbracedwithgirts(blockingbetweenstudsnearthemid-point)orifinterioror

exteriornishesarenotprovided.Ifnishisprovidedononesideofthewall,girtsarenotrequired.

Longerstudsaremoresusceptibletobuckling.Thisiseasytounderstandifyouholdbothends

ofayardstickandtryandpushtheendstowardeachother.Theyardstickbucklesveryeasilyin

themiddle.Thisismoredifcultwithasix-inchrulerofthesamematerial.

Whereanotheroorlevelistobeaddedtoahome,specialconsiderationshouldbegivento

studwalls,whichmaynotbestrongenoughtocarrytheaddedweight.


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CONDENSATION Rotormoldcausedbycondensationinexteriorwallsisaconcern,especiallywhereinsulation

INCOLD isupgradedinolderhouses,andwithouteffectiveair/vaporbarriers.Thiscannotbedetected

CLIMATES duringavisualinspectionanditmaybealongtimebeforethedamageisnoticed.Insome

cases,peelingexteriorpaintsuggeststhatwallcondensationisaproblem.

Thisistypicallyaseasonalproblemincoldclimates,withthecondensationoccurringduringthewintermonthsonly.Warmmoistairentersthewallfromthehouse.Asitpassesthrough,

theaircools.Coolaircannotholdasmuchwatervaporaswarmair.Condensationforms

insidethewallastheaircoolsandgivesoffitswater.

LOWQUALITY Poorqualitystudsorstudsthatwarpandbowcanleadtounevenwallsurfacesinnewhomes.

LUMBER Thebowedortwistedstudshavetoberepairedorreplaced.

GREENLUMBER Buildingwithlumberthatistoowetorgreencanresultinproblemssuchasshrinking,warp-

ing,orbowing.

6.1.2.1BalloonFraming:Balloonframingwascommoninthelate19thandearly20thcentu-

ries. This wood-frame construction technique used conventional studs andoor joists.

However,thewallstudswerecontinuousfromthe

foundationup to theroof line. Theconstruction

process involves setting up the wall studs, and

thenhangingtheoorsystemsfromthem.When

completed,thisresultedinarigidstructure.One

disadvantageisthatarecanmoveveryquickly

upthroughthecontinuousstudspaces.

6.1.2.2 Platorm Framing: Platform or Western

framingisslightlydifferent.Awoodoorjoistand

suboorsystemisprovidedontopofthefounda-

tions.One-storystudwallsarebuiltontheoor.Ifthehouseistwostories,asecondoorplatformis

assembledontopofthestuds,andthenasecond

studwallisbuiltontopofthisplatform.Thiscan

beextendeduptoformathree-storyhouseaswell.

The advantagesof platform framing are ease of

installationandlowermaterialcosts.


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6.1.3SteelFrame:Steelframewallsmaybeload-bearing,carryingtheweightoftheroof

andoorsdowntothefoundations.Theymaybeinteriororexteriorwalls.Steelframewalls

mayalsobeusedasnon-load-bearingpartitionwalls.Whilewoodframingmembershave

traditionally dominated residential construction, the use of lightweight steel framing is

increasing.

StructuralframingelementsaregenerallyeitherC-shapedorU-shaped.C-shapedelements

aredesignedasload-bearingelements,suchasstudsandjoists,whiletheU-shapedpiecesare

tracks,orchannelsthatholdtheload-bearingcomponentsinplace.Insteelconstruction,

tracksreplacethesillsand topplatesusedinwood-frameconstruction.Non-load-bearing

wallsaretypicallythinner,butareotherwisesimilartoload-bearingwalls.

CommonProblemswithSteelFrameWalls

THERMAL Assteelismuchmoreconductivetoheatthanwood,thethermalefciencyofsteel-framed

BRIDGING wallsismuch lessthanthatofawood-framedwall.Steelframedwallsmayhavehalfthe

insulatingvalueofwoodwalls.Thethermalbridgescreatedbysteelstudscanbereduced

throughtheuseofinsulatedsheathingontheoutsideofthestuds,andwiththeuseofwider

studspacing.

CORROSION Someoldersteelframewallsdidnotadequatelydealwiththermalbridgingissues,leadingto

condensationandcorrosionofthesteelstuds.Corrosionmaybeanissuewheneverthereisa

condensationorwaterleakageproblem.

IMPROPER Steel studs usually comewith pre-punchedholesfor plumbingand electricalwiring and

HOLES shouldbeinstalledsothattheseholesarealignedforeasyinstallationofthemechanicaland

electricalsystems.Thereareindustry-speciedrequirementsforotherholes.Improperholes

canweakenthewall.


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REINFORCEMENT Woodnailingstripsareoftenrequiredtoallowdoorjambsandothertrimtobenailedtothe

MISSING/ framing.Finishingscrewsmaybeusedinsteadofnails.Wallshavetobereinforcedinsome

INADEQUATE areas,suchaswhencabinetsaretobesecuredtonon-load-bearingsteelstuds.

6.1.4Brick/StoneVeneer:Abrickorstoneveneerwallhasastructuralwood(ormetal)frame

innerwall,anda four-inchthickmasonryoutersection(veneer),whichdoesnothaveanyload-bearingresponsibility.Typically,metaltiesareusedtosecurethemasonrytothewood

framewall,andtherearenoheadercoursesinthemasonry.Theabsenceofheadersidenties

aveneerwallinmostcases.Mostsolidmasonrywallshaveheaders.

Veneerwallshavebeenthemostcommonmasonrywallsinsingle-familyhomesinmany

partsofAmericasinceabout1970.


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RAINSCREEN Sincetheearly1970s,veneerwallshavehadweepholesprovidedatthebottom.Amodern

PRINCIPLE veneerwallusesarainscreenprinciple.Thisanticipatesthatwinddrivenrainwillpassthrough

amasonrywall,andasaresult,aone-inchairspaceseparatesthemasonryandthewoodstud

wall.Waterrunsdowntheinnerfaceofthebrickortheoutersurfaceofthesheathingand

drainsoutthebottom.

Atthebottomrowofmasonry,everyfourthverticalmortarjoint(typically)isleftopen.A

ashingatthebottomofthewallcavitydirectswateroutthroughtheweepholes.Theash-

ingpreventsthewaterfromenteringthefoundation.Weepholesarealsousedabovedoor

andwindowopenings.

Weepholes also allow pressure balancingon either side of the masonry. The air in the

cavitybehindthemasonryispressurizedaswindblowsagainstthewall,reducingthepressure

differentialacrossthemasonry.Thisreducestheamountofwaterdriventhrough.

Avariationonweepholesisropewicksineveryfourthmortarjointinthebottomrowof

masonry.Whereweepholesorwicksarenoted,thewallismasonryveneer.

CommonProblemswithBrickorStoneVeneerWalls

FOUNDATIONS/ Although the veneer has no load-bearing responsibilities, it must sit on a foundation

CONNECTIONS builttosupporttheweightofthebrickorstone.Ifthefoundationisnotsubstantial,theveneer

wallmaycrackand/orsettleawayfromthewood-framewall.Iftheveneerisinadequately

tiedtothewood-framewall,themasonrymaybulgeorpullaway.Thisisanunsafecondition.

DETERIORATED Deterioratedmasonryormortarcanleadtoseriousproblems.Intheworstcases,theveneerwallhastoberebuilt.Mostbrickisnotdesignedtobeincontactwiththesoil,andshouldbe

keptwellabovegrade.

WEEPHOLES Ifweep holes are lled or omitted, water can collect in the wall cavity, damaging the

sheathingandstuds.


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FLASHING Similar results occur if the

ashingisinappropriateorthe

spacebetweenthemasonryand

sheathingislled.Theashing

cannotnormallybeseenduring

aninspection.

CORBELLING Excessivecorbellingcanmakea

wallunstable.(SeeSection6.1.1)

METALANGLES In some cases, the masonry

veneer is supported on steel

anglesboltedtothefoundation.

Ifthereisanymovementatall,

themasonrymaycrack,bulge,or

pullawayfromthewallbehind.

6.1.5InsulatingConcreteForms(ICFs): Insulating Concrete

Forms(ICFs)areeitherpanelsor

interlocking blocks that are

joinedtogethertocreateform-

work for concrete. The forms

themselves are made out of

insulation, either rigid foam,

suchaspolystyrene,oracombi-

nation of concrete and foam

insulationorwoodchips.Plastic

ties may be used to hold theinnerandouterformstogether.

Oncetheformsareinplace,con-

crete ispoured into theforms,

lling the spaces. Rather than

removetheforms,asinconven-

tional concrete work, they are

leftinplacetoactasinsulation.

ICFwallsarealsousedasfoun-

dationwalls.

Afterahomeisbuilt,itmaybedifculttoidentifythewallcon-

struction.


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INSULATION ICFwallstypicallyprovideatotalR-valueof22,aboutthesameasa2x6studwall.Thesewalls

alsoavoidthermalbridges (areasofhighthermalconductivity)thatarecommoninwood

studwalls.ICFwallsarealsoairtight,whichisgoodforenergyperformance.

REINFORCEMENT ICF walls may include vertical and/or horizontal steel reinforcing bar, especially around

windowanddooropenings.

LEDGERS WhereoorsmeetICFwalls,theymayeitherrestonasillplateonthetopoftheICFwall,or

bearonaledgerboardsecuredtotheICF.

OPENINGS Inmostcases,woodframingisattachedtotheICFatdoorandwindowopeningstoallow

windowframesanddoorjambstobesecured.

ELECTRICAL Electricalwiringandoutletsgenerallyrequiretheinsideformtobe cutaway.Theshallow

WIRING depthoftheformmeansthatwiringmayrequireprotectionfrommechanicaldamage,and

receptaclesneedshallowboxes.

CommonProblemswithICFWalls

WOOD Whilepolystyreneisnotafoodsourceforpests,somewood-destroyinginsectswillnestin,or

DESTROYING travelthrough,thefoam.SomeICFproductscontainchemicalprotection,andsomeICFinstal-

INSECTS lationsusemechanicalbarrierstoprotectagainstinfestation.

RENOVATIONS ItismoredifculttocreateanewopeningoralteranexistingopeninginanICFwallthana

woodframewallbecauseofthepouredconcrete.

6.1.6OtherKindsoWalls

6.1.6.1Log:Modernloghomesutilizepreciselycutlogs,keyedtogether,withgasketsbetween

logs,whileolderlogstructuresaremuchrougher.

SIDINGS Manyolderloghomeswerecoveredwithwoodsheathingsuchasclapboardontheexterior

assoonasthehomeownerscouldaffordit.Stuccowasalsousedontheexteriorinsomecases

andplasterwasoftenappliedontheinterior.Someoldloghomeslookquitedifferentthan

theydidwhentheywerebuilt.Thefoundationsweretypicallystone,andwoodshinglesor

shakeswereoftentheroongmaterial.

CHINKING Chinkingwastraditionallyusedtollthegapsbetweenthelogs.Thiswastypicallyamortar

madeofclay,sandandbinderssuchasanimalhair.Wheregapswerelarge,stoneswould

oftenbettedinbeforethechinkingwasapplied.Duetotheconsiderablemovementdueto

expansionandcontractionoflogsacrossthegrain,chinkingusuallyhadtoberedoneevery

year,atleastinpart.


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CommonProblemswithLogWalls

WOOD Traditionallogconstructiontodayisarelativelyexpensivewaytobuild.Further,woodtends

SHRINKAGE toshrinkandexpandwithchangesinmoisturecontentmuchmoreacrossthegrainthanit

doeswiththegrain.Alogwallgrowsshorterasthewooddriesandtallerwhenthewoodis

wet.Awoodstudwallwillshrinkandexpandmuchlessbecausethewoodgrainisvertical

ratherthanhorizontal.

Ifwoodchangesitsmoisturecontentfrom19%to5%(typicalinahouse),itslengthmay

changeby0.1%alongthegrain,butitswidthmayshrinkby2.5%acrossthegrain.Thismeans

aneight-footlongstudmayonlyshrink1/10inch,whileastackoflogseightfeethighmay

shrinkby2-1/2inches.Thiscanbeasignicantproblemwithwindows,doorsandotherbuild-

ingcomponentsattachedtoalogwall.

CHINKING Regularmaintenanceis required in chinking thegapsbetween thelogs intraditionallog

homes.Themodernmaterialsnowavailableperformmuchbetter.

ROT/INSECT Rotisacommonproblemwithlogsatthebottomofthewall(wheretheymayhavebeenin

DAMAGE contactwithearth)onoldhomes.Thisisnotlikelytobeaproblemwithmodernloghouses

builtonconventionalmodernfoundations.Loghomesaresusceptibletoinsectdamage,of

course.

CONCEALED Wherethelogshavebeencoveredwithsiding,concealedwaterdamageispossible.

DAMAGE

6.1.6.2Post andBeam:This typeof construction,withwoodmembersmuchlarger than

conventionalwood-frameconstruction,isnotcommon,althoughitcanbefoundonolder

countrypropertiesandwascommonlyutilizedforbarns,mills,churchesandotherlargebuild-

ings.Thereareprefabricatedkitsavailable.Othernamesforthistypeofconstructionincludetimber,heavytimberorsemi-millconstruction.

Thisbuildingstyleusesasmallnumberoflargewoodbeamsandposts.Thisisverydifferent

fromconventionalframingthatusesalargenumberofsmallerwoodstudsandjoiststocarry

theloadsdowntothefoundations.

Traditionally,theheavypostsandbeamsweresolidwood.Inhomesbuilttoday,builtupor

glue-laminatedbeamsandpostsarealsoused.Intheoriginalversions,theheavywoodposts

wereoftenaredoutatthetoptoincreasestrength.Afeatureofthesehomeswastheway

thewoodsectionswereconnected.Verysophisticatedmortiseandtenonconnectionswere

utilized,asweredovetailjoints.Manyofthehomeswereassembledwithoutnails,wood

dowelsoftenbeingusedintheirplace.


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The walls were often 2-inch thick planks, installed horizontally or vertically. In some

casesthesewereloadbearing,althoughforthemostparttheysimplyprovidedaweather

tightskin.

Thesehouseswereexpensivetobuildbothintermsofmaterialsandlabor.Largepiecesof

goodqualitylumberhavebecomehardertoobtain.Becausethewoodcomponentswereveryheavy,andsophisticatedjointconnectionswereused,constructionwaslaborintensive.

CommonProblemswithPostandBeamWalls

LACKOF Since the skeleton consisted of a few large components and relatively few connections,

RIGIDITY rigiditycouldbea problem,particularlywherethesheathingdidnotperformastabilizing

function.Becauseoftheintricacyofsomeoftheconnections,therewasagooddealofroom

forerror,andapoorunderstandingofloadtransmissionscouldleadtoconnectionfailures.

EXPANSION/ Theverylargetimbersundergosignicantdimensionalchangeswithchangesinmoisture

CONTRACTION content.Thesebuildingsarenotstatic,expandingandcontractingwithchangesinhumid-ity.Astimbersdriedout,checkingoftendeveloped.Checksarelongitudinalcracks,parallel

tothegrainthatwidenastheygetfurtherfromtheheartwood.Inmanycases,thisisnota

structuralconcern,althoughalargecheckrunninghorizontallythroughabeamdoesreduce

itsloadcarryingcapacity.Wherecontinuouscheckinginapostcouldleadtobuckling,steel

clampsareprovidedaroundtheposts.

FOUNDATION Becauseoftheskeletalnatureoftheframing,largeconcentratedloadswerecarriedtothe

ground.Foundationsystemswereoftentooweakinareasofconcentratedloads,andmuch

strongerthantheyhadtobeinotherareas.

CONNECTIONS Thesebuildingsrelyonrelativelyfewconnections.Poorlymadeconnectionsordamagebyrot

orinsectscanbemoreseriousthanonframeconstruction. SPECIALIZED Sincethistypeofconstructionisspecialized,andnotseenfrequently,localauthoritiesand

INSPECTION professional home inspectorsmay not be familiar with it. In some cases, a specialist is

engagedtocommentonpostandbeamstructures.

REPAIR Repairorreplacementofcomponentsofpostandbeamconstructionisoftendifcultwithout

compromisingtheaestheticorarchitecturalappealofthehome.Thestrengthofstructural

componentsmustbedemonstratedusingengineeringcalculations,ratherthantables.


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6.1.6.3Panelized:Panelizeddescribesamethodofconstruction,ratherthanaspecicsystem.

Intraditionalframing,theindividualcomponentsofthehouse,suchasstuds,joistsandrafters,

arebroughttothesiteandthehouseisbuiltfromindividualpieces.Inpanelizedconstruction,

largepanelsarebuiltoff-site,thenassembledon-siteandsecuredtothefoundation.These

panelsmaymakeuptheoors,walls,ceilingsandroofsofthehome.

Therearevaryingdegreesofpanelization.Panelsmaybesimplestructuralsections,orthey

may include siding, insulation, wiring and even interior nishes. Panelized construction

mayutilizewood framing,steel framing,or a combination of the two. The panels often

includeupgradedinsulationtreatmentandlessthermalbridgingthanfoundinconventional

construction.

Oncethehomeisconstructed,thereisgenerallyverylittledifferencebetweena site-built

homeandapanelizedhome,althoughmanufacturersmaintainthatthebetterworkingenvi-

ronmentandqualitycontrolpossibleinafactory,resultsinbetterbuilthomes.

6.1.6.4StructuralInsulatedPanels(SIP):StructuralInsulatedPanels(SIPs)areonetypeof

panelizedconstruction.SIPsincludethestructuralmember,insulation,airbarrierandexteriorsheathing.Thesetypesofpanelsaresometimescalledstress-skinpanelsbecausethewood

outerlayersactliketheangesofasteelI-beam.Theinsulationactsastheweb.Weendup

withastrongstructuralmemberwithoutusingalotofmaterial.

StructuralInsulatedPanelsaretypically31/2to51/2inchesofexpandedpolystyreneinsula-

tionsandwichedbetween4-footby8-footplywoodororientedstrandboard(OSB)panels.

Theinsulationistypically11/2inchessmallerthantheskinatthetopandbottom,sothe

panelscanreceivesillplatesandtopplates.Somepanelshaverecessesintheinsulationat

thesidestoacceptplywoodorOSBpiecestojoinadjacentpanels.

ELECTRICAL Manypanelsincludehollowchasesintheinsulationtoaccommodateelectricalwiring.Foam

WIRING hastoberemovedtomakeroomforelectricalboxes.

OTHER Similarproductsarealsomade,replacingthewoodwithsteel,aluminum,concreteandber-

MATERIALS glass.Insulationmaterialsaremostoftenexpandedpolystyrene,butcanbepolyurethaneor

othermaterials.


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CommonProblemswithPanelizedWalls

Rot, insect attack, mechanical damage, re damage can all be problems with wooden

components.

WOOD Whilepolystyreneisnotafoodsourceforpests,somewood-destroyinginsectswillnestin,

DESTROYING ortravelthrough,thefoam.SomeSIPproductscontainchemicalprotection,andsomeSIP

INSECTS installationsusemechanicalbarrierstoprotectagainstinfestation.

6.1.6.5RammedEarth:Asthenamewouldsuggestearth,orsoil,istheprimarycomponent

ofarammedearthwall.Nativesoilcansometimesbeused,butascreenedengineeredsoilis

mostoftenused.Idealsoilsareaboutthreepartssandtoonepartclay.

Forms are constructedon conventional foundations.Theformshave plumbing pipes and

electricalconduitplacedpriortopouringthesoil.Athickmixtureofearth,cementandwater

ispouredintotheformsinlayers(typically8inchesthick).Thereistypicallylessthan5%

cementand5to10%watermixedintothesoil.Eachlayeriscompacted(toaboutveinches),andanotherlayeristhenaddedandcompacted.Pneumatictampersaretypicallyusedto

compactthesoilintheforms.Theprocessisrepeateduntilthewalliscomplete.Analternative

approachusesapumptoshootthemixtureintoone-sidedformswithairpressure.

Whenthe forms areremoved, a rough surface ispresented. This canbeanarchitectural

feature,orthewallscanbecoveredwithplasterontheinteriorandstuccoontheexterior.

Finishedwallsaretypically12to18inchesthick.

CommonProblemswithRammedEarthWalls

POOR Rammedearthhomesarelesspracticalinnorthernclimateswherethethermalmassofthe

INSULATION wallsdoesnotprovidegoodinsulatingperformance.Theinsulatingvalueofan18-inchthick

wallmaybeR-4orR-5,wellbelowmodernstandardsincoldclimates.

MOISTURE Likemany building systems, moisture is the enemy.While rammed earthwalls are not

damagedbyoccasionalmoisture,durabilitymaybeanissueinwetclimates.Sometypesof

soilarealsomoremoisture-resistantthanothers.Exteriorsealantsareusedinsomecasesto

protecttheearthwallsfrommoisture.Largeroofoverhangsandraisedfoundationshelpkeep

thewallsdry.

DAMAGE Mechanicalormoisturedamagemayresultinmissingorloosesectionsofthewallcoveringor

thewallitself.Areasclosetogrademaybemorevulnerable.

WINDOWSILLS Windowsmaybeinstalledclosetotheinteriororexteriorwallface.Fromaperformancestandpoint,windowsclosetotheexteriorsurfacearepreferred,sincethiseliminatesawide

exteriorwindowsillthatwilltrapwater.


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6.1.6.6StrawBale: Strawbalewallscanbe loadbearingstructuralmembers,carryingthe

secondoorandroofloads,orthebalesmayllinbetweenorwraparoundawoodpostand

beamframe.Ineithercase,thebalesprovidetheinsulationaswellasthebaseforinterior

andexteriornishes.

Strawisthestalkofgrainssuchaswheat,barley,rye,oatsandrice.Strawshouldnotbeconfusedwithhay,whichisgrassthatisfoodforhorses!Horseswouldnotappreciatebeing

fedstraw.Strawisgenerallyconsideredawasteby-productof agricultureandanuisance

becauseitisslowtodecompose.

Strawbalesusedforbuildingweigh50to90poundseach.Smallbalesmaybe14inchesby18

inchesby36inches.Thelargestbalesmaybe18inchesby24inchesby48inches.Thewallsare

typically13to24inchesthickplusthethicknessofthenishesontheinsideandoutside.

Balewallssitonconventional foundationsthat,withsomeexceptions,shouldbe aswide

asthebales.Thereisusuallyamoisturebarrierbetweenthetopofthefoundationandthe

rst row ofbales. Vertical steelreinforcing bar (re-bar)projects 12 inches out the top of

thefoundationtosecurethebalestothefoundation.There-baristypically1/2inchdiameterandisplacedinthecenterofthefoundation,everytwofeetalongthewalllength,andwithin

12inchesofallcorners.

Thebalesarestackedlikelargebricksintoawallconguration,andaresometimesconnected

toeachother with steelrebar, orwood orbamboo stakes.Water pipesin the balesare

installedincontinuoussleevestoprotectthebalesfromdamageduetoleakage.

Stuccoov

Documents

Structure , Home Inspection Course and Exam , North America , Canada