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Dan

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Final Analysis Property Inspections LLC

Dan

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THE HOME REFERENCE BOOK ©

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INTRODUCTION

1.0WhyBuildingsMove

GRAVITY What causes structures tomove? – In a word, gravity.Gravityisconstantlyworkingtogetthingsclosertotheground.Strongstructuresresistgravity.

STRUCTURE Therearetwocommonwaysastructuremaygiveintogravity.

FAILURES a)If it is sitting on somethingthatisnotstrongenough,thegroundbelowitwillfail.Bet-ter to build on bedrock thanquicksand.

b)Ifthestructureitselfisweak,it will not support the loadsimposedonit.Thetotalloadismadeupofthefollowing–Deadload–theweightofthestructureitself,Liveload–furniture,people,wind,snowandearthquakes.

WIND Windactsintermittentlyonstructures.Windforcescanpush,pullorliftbuildings.Buildingsmustbestrongenoughtoresistthelateralandupliftforcesofwindaswellasthedownwardforceofgravity.Hurricanesandtornadoesareextremewindconditions.Theseoftenresultinmechanicaldamagecausedbyprojectiles.

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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EARTHQUAKES Earthquakesalsocreateforces,whichcancausestructuralfailures.Likewind,theseforcesare ANDEROSION intermittentandvariableandcanpush,pullorliftbuildings.Erosionisaslowerformofearth

movement,butitcanhaveadevastatingeffectonstructuresaswell.

COMPONENT House components may fail because they were poorly built with improper materials, or FAILURES the materials were poorly assembled. Rot, insects, fire and mechanical damage can cause

well-builtstructurestofail.Rustcanattackmetalcomponents.

COMPRESSION Whatforcesaffectindividualstructuralcomponents?Thetwobasicforcesarecompression ANDTENSION andtension.Amaterialisundercompressionwhenitisbeingpushedfrombothends.Amate-

rialisundertensionifitispulledon.Componentsincompressiontendtogetshorteroraresquashed.Componentsundertensiontendtogetlongerorarepulledapart.Manybuildingcomponentsfeelacombinationofcompressionandtension.Some building materials are good in compression, others work well in tension and someperform well in both. A pile of bricks is very good in compression; you can stand on it.However,itisverypoorintension.Achildcanpullthepileapart.Achain,ontheotherhand,isverygoodintension.Youcanpullquitehardonbothendsandnothingwillgive,butthemomentyoutrytopushonit,thechaincollapses.Itisnotverygoodincompression.

SHEARINGAND Differentmaterialsfailindifferentways.Shearingandbendingarecommonmodesoffailure. BENDING Shearoccurswhenadjacentfacesofamaterialmoveinoppositedirections.Whenabeam

splits,orabrickcracks,itisbecauseofshear.

Bendingismovementwithoutshearing.Aplankspannedbetweentwochairswillbendifsome-onestandsonit,particularlyiftheystandnearthemiddle.Theupperhalfoftheplankispushedtogetherundercompression;thebottomhalfgetsslightlylongerbecauseitisintension.

Buildingcomponentsthatfailbybendingaresaidtosagorbuckle.Somematerialscanbendasignificantamountwithoutlosingtheirstrength.Brittlematerials,however,donotbendmuch before they break. Ductile materials do. Ceramic tile is brittle, rope is ductile. Someductilematerialsareelastic.Thismeanstheywillgobacktotheiroriginalshapeafterbeingbent.Arubberballiselastic;anailisnot.


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DEFLECTION Deflectionisamildformofbending. If structures deflectjustalittle,peopledonotmind.Building codes stipulate howmuchdeflectionisacceptable.Atypical floor joist, for example,isallowedtodeflect1/360thofitsspan.

MATERIAL What makes a good building SELECTION material? It should be good at

resisting the forces of tensionand compression. It should becheap, easy to work with, light,long lasting, water, rot and fireresistant,andstableunderdiffer-enttemperatureandhumiditylevels.Noonematerialdoesitall.Thatiswhyhousesaremadeofmanymaterials.Woodisoneofthebettermaterialsforsmallbuildings.Itisrelativelygoodinbothtensionandcompression.Steelisalsogoodinbothtensionandcompression.

Buildingmaterialsarechosenbasedoncost-effectiveness.Thegoalistoassembleastructurethatwillperformwellforassmallacostaspossible.Thiscanleadtosomeverysmallmarginsofsafetyand,ofcourse,somefailures.Asnewmaterialsaredeveloped,theyaretried;insomecases,withgreatsuccess;inothercases,withverypoorresults.

Thestructureisbyfarthemostimportantpartofthehouse.Thesafetyandusabilityoftheentirehomedependsonitsstructuralintegrity.Sincemanystructuralcomponentsareburiedbelowgradeorbehindfinishes,muchofthestructuralinspectionisdonebylookingforevi-denceofmovement.Wherenomovementhasoccurred,imperfectionsmaygoundetected.Newinteriororexteriorfinishesandpatchingworkmayconcealimperfectionsovertheshortterm.Inthesecases,problemswillnotbeidentified.

REPAIRS Structuralrepairscanbeverycostly,andinsomecasestheproblemissoseverethatthebuild-ing is torndown. Inmanycases,astructuralengineershouldbeconsultedbeforemakingrepairs.Anincompleteunderstandingofaproblemmayleadtoincorrectsolutionsandalife-threateningsituation.

CHAPTER In this chapter we’ll look at foundation configurations briefly, then discuss the various ORGANIZATION structurecomponentsoneatatime,startingwiththefootingsandfinishingwiththeroof.

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2.0Configuration

Homesmayhaveabasement,acrawlspace,both,orneither.Manyhouseshavepartialbase-mentsand/orpartialcrawlspaces.Theconfigurationisdeterminedbyclimate,cost,regionalbuildingpracticesandrestrictionsimposedbythebuildingsite.Inareaspronetohurricanesandflooding,buildingsmaybebuiltonpostsorstiltstokeepthehomewellabovegrade.

2.1Basement

Where frost footings are required, a trench is needed around the house perimeter for thefootingandfoundationsystem.Sincethisexcavationisnecessary,itisnotmuchmoreexpen-sivetodigabigholeandcreateabasement.Inwarmclimateswherefrostfootingsarenotrequired,basementsarerare.

Thebelow-gradespaceisinexpensivetobuildoncetheholeisdug,andcanbeusedforany-thingfromroughstoragetolivingspace.Basementscommonlycontainthemechanicalandelectricalsystemsandmayincludeaworkroomandlaundry(althoughthelaundryisupstairsinmanymodernhomes).Gameroomsandfamilyroomsareoftenlocatedinbasements,andcompleteapartmentscanalsobebuiltbelowgrade.

Disadvantagesofbasementsincludethesusceptibilitytowaterleakageandlackofnaturallight.Windowsinbasementsareusuallysmallandhighonthewall,sincemostofthewallisunderground.Basementceilingsareoftenlow,andevenifthereisnowaterleakage,theycanbecoolanddamp.

2.2Crawlspace

Whereatrenchisdugforthefoundations,andtheearthunderthehousefloorisnotremoved,acrawlspaceiscreated.Itmayhaveanearthfloor,althoughaconcreteslabismoredesirableforstorageandmoisturecontrol.Manymoderncodescall forcrawlspacestobe36 incheshighwhereaccessmustbegained,althoughmanyoldcrawlspacesareless.Someareentirelyinaccessible.Restrictedaccessmakesinspection,maintenanceandrepairmoredifficultandexpensive.

VENTING Crawlspacesareoften ignoredfor longperiods.Wheremoisture levelsarehigh,structuraldamage,duetorotandinsectactivity,cangounnoticed.Somebuildingstandardscallforonesquarefootofventingforevery500squarefeetofcrawlspacearea.Thisisrarelyprovided.Wherethecrawlspaceisdry,thismaynotbeaproblem.


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2.3Slab-on-Grade

Inthistypeofconstruction,apouredconcretefloorrestsdirectlyontheground.Theconcreteslab is at least three inches thick and may or may not be reinforced with steel bars.Immediately below the slab, a moisture barrier is typically laid over about six inches ofgravel.Inmodernconstruction,insulationisoftenprovidedbelowtheslab.Slabsaretypicallysupportedbyfootingsandfoundations.

Thereareseveraltypesofslab-on-grade construction, includ-ing monolithic slab, supportedslab,andfloatingslab.Amono-lithicslabisaconcretefloorandfoundation all poured as one.Thiscanbethoughtofasafloorslab that is thicker around theedges.

A supported slab is not pouredtogether with the founda-tion, but it does rest on thefoundation. The footings andfoundation wall are installedfirst,witha ledgeat thetopofthe foundation to support theslab. Basement floor slabs areoftensupportedslabs.

Thefloatingslabisentirelyinde-pendentofthefoundation.Thefoundation is poured or builtfirst. The slab is not supportedbyorconnectedtothefounda-tion.Thistypeofslabiscommoningarages.

From an inspection and main-tenance standpoint, slab-on-grade is more restrictive thanhomes with basements orcrawlspaces because none ofthefoundationisaccessible.

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SYSTEMS Basementorcrawlspacefloorsareoftenleftasexposedconcrete.Problemswithwateror CONCEALED insectinfestation,forexample,canbepickedupearly.Withslab-on-grade,theconcreteslab

isnormallycoveredbysubflooringandfinishflooring.Problemscangoundetectedforsometime.

Wheretheslabispoorqualityconcrete,toothin,ormissingthereinforcingbar,thefloorispronetocrackingandshifting.Subsurfaceerosioncanalsoresultinslabfailure,ascanareasexcavatedforplumbingorheatingpipes.This leadstobroken,unevenfloorsurfaceswithmorepointsofentryforwaterandinsects.Substantialshiftingcandamagetheplumbing,heatingandelectricservicesburiedinorbelowtheslab.Expansivesoilscanheavetheslab,resultinginsimilarproblems.

3.0Footings

Thefunctionoffootingsistotransmittheweightofthehousetothesoil,withoutallowingthehousetosink.Footingsare locatedbelowthefoundationwalls,orattheperimeterofslabs,andbelowcolumnsorpiers.Thehorizontalsurfaceof thefooting is largerthanthefoundation,sotheloadofthehousecanbespreadoutoverawidearea.Footingsaretypically16to24incheswideandsixinchesto16inchesthick.Incoldclimates,footingscarrythehouseloadsbelowthefrost line.Theheavierthebuildingandtheweakerthesoil,the largerthefootingshouldbe.

Footingsmaybeconcrete,brickorstone.Inmodernconstruction,mostfootingsarepouredconcrete,oftenreinforcedwithsteelbars.

FOOTINGTYPES Stripfootings(alsocalledspreadfootings) run continuously be-low foundation walls, typicallyaround the building perimeter.Pad footings (also called spotfootings) are smaller and typi-callysupportcolumnsorpiers.

PIERAND Pier and grade beam construc- GRADEBEAM tioniscommoninareaswithex-

pansivesoils.Concretepiersarepoureddowntoadepthwherethe soils are stable. Gradebeams,whichoftenformfoun-dationwalls,spanbetweenthepiers. These grade beams areoftenreinforcedconcrete.


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CommonProblemswithFootings

When the footings fail, the entire house moves. This is often a very serious problem. It isalmostalwaysexpensive,andsometimesimpossible,tocorrect.Sincethefootingsarelocatedbelowthesoil,theycannotbeseen.Itisoftendifficulttoknowwhytheyhavefailed.

Settlementisthemostcommonformoffailure,althoughheavingiscommonincoldclimatesduetofrostexpandingthesoilbelowfootings.

Sometimes footings fail in onearea, and in most cases thefailure is not uniform, (i.e. thebuilding does not sink straightdown but leans to one side oranother).Often,onepartofthehouse will pull away from therest. This leads to cracking ofinterior and exterior wall sur-faces.

SETTLEMENT– Soils prone to compaction or WEAKSOILS movementdonotsupportfoot-

ingswell.Thisincludesrecentlydisturbedsoil.Forexample,ifanexcavation for a foundation isdug too deep, then backfilled to the correct depth, the disturbed soil under the footing islikelytocompactoverthefirstfewyears,resultinginbuildingsettlement.

SETTLEMENT– This is not common on pro- ABSENCEOF fessionally-built houses, but FOOTINGS may occur in casual construc-

tion as well as on porches andpoorly built additions. Somehomeswerebuiltonmudsills–woodbeamslaidonthegroundwith walls built on top of thebeams. These mud sills are re-placed with a foundation andfooting system as the sills rot,heaveorsettle.

SETTLEMENT– Thesemayerodeorweakensoil UNDERGROUND below the footings, causing STREAMS severebuildingsettlement.Itis,

of course, very difficult to locate and trace underground streams. They often flow only atcertaintimesoftheyear.

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SETTLEMENT– Settlement may be the result of poor design, or an additional load that has been added. UNDERSIZED For example, when a second floor is added to a bungalow, the weight may cause the FOOTINGS footingstosink.Theadditionalweightofamasonrychimneycanalsocauselocalizedfooting

failure.

SETTLEMENT– Thefootingmustbestrongenoughnottobreakapartunderaload,andmustbeabletostand FOOTING uptocontinuousexposuretodampsoil. DETERIORATION

SETTLEMENT– Ifthebasementfloorislowered,thereistheriskthatthefootingswillbebrokenoffonthe UNDERMINED insideorwilllosetheirsupport.Evenifexcavationisnotdonebelowthefootingsbutdown ORCUT tothebottomofthem,thelateralsupportforthefootingmaybelost,andthefootingand FOOTINGS foundationwallmaymoveinward.

SETTLEMENT/ Whenabasementfloorislowered,thefootingsshouldbeunderpinned(loweredand,insome WALLFAILURE– cases,enlarged).Alternatively,onlythecentralsectionofthebasementshouldbelowered,to LOWERED avoiddisturbinganyofthesoilnearthefootings.Dependinguponhowmuchthebasement BASEMENT floor is lowered, the required clearance from the footings varies. A soils engineer is often FLOORS consulted and a concrete curb (also called a bench footing or Dutch wall) may be needed

aroundtheinsideedgeofthefootingstoensuretheyarenotcompromised.Buildingsettle-mentandfailureoffoundationwallsarebothriskswhenloweringbasementfloors.

Oneofthedangersinloweringbasementfloorsistheincreasedriskofbasementleakage.Noticeinthefollowingillustrationshowthedrainagetileoutsideisnolongerinthecorrectlocationoncethefloorislowered.Itistoohightobeeffective.

Whenexcavationisdoneontheexterior,(e.g.foranadditionorswimmingpool)thefootingscanbedamagedorunderminedinasimilarfashion.


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SETTLEMENT– Housesbuiltonorclosetoslopesmaybesubjecttofailuresasaresultofsoilmovingdown LOTSLOPE theslope.Thismaybeaslowsteadyprocessorasuddeneventtriggeredbyheavyrainsfor

example.Thiscanbeextremelycostlytocorrect.

SETTLEMENT– Houses built on sloping lots may be more prone to footing and foundation failures. The CUTAND chancesofbuildingondisturbedsoilareincreasedonlotssuchasthese.Effortsmadetolevel FILLLOTS andterracethelotmayresultin

soil being cut out of the hill toform a level terrace under thebackhalfofthehouse.Thissoilis then used as fill in the adja-cent area where the front halfof the house is to stand. Thedownhillhalfofthehousemaybebuiltonfillthatmaynotbewell compacted or may not beabletostayinplaceandsupportthehouse.

On sloping lots, large lateralearth thrust and hydrostaticpressurecanbebuiltupbythesoilonthehighsideofthehome.Waterrunningdowntheslopeisblockedbythebuildingandaccumulateshere.

Onthedownhillside,thefootingsmaynotbedeepenoughincoldclimates.Frostheavecanresultwherethefootingsarelessthanfourfeetbelowgrade.Thesideofthehousewiththelowergradeoftenhasawalk-outbasement,andchancesofafootingbeingtooshallowaregreatesthere.

SETTLEMENT/ Someclaysoilsthatexpandandcontractsignificantlywithdifferentmoisturecontentsmay HEAVING– alsoresultinfailure.Theseexpansivesoilscanheavefloorsandfoundationswhentheyget EXPANSIVESOILS wet.Whentheydry,theyshrinkandallowthebuildingtodrop.Thisisasignificantcauseof

housestructureproblemsinsomeareas.

Tree roots can affect the moisture content of soils noticeably. Most soils have strengthsthatchangewithdifferentmoisturecontents.Someclaysoilstrengthschangedramatically.Thesearepoorbuildingsoils.Siltsarealsopoorbuildingsoils,inmanycasesmuchweakerthanclay.

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EXPANSIVE Whereexpansivesoilsarecommon,heavingsoilbelowtheslabcanpushtheslabupwards SOILSAND atthecenterorattheperimeter,breakingtheconcreteanddamagingutility lines.Where SLAB-ON- thesesoilsarecommon,theslabsaresometimespost-tensioned.Thismeanstherearesteel GRADEHOMES reinforcing cables laid within

theslabandprojectbeyondtheslab edge. The cables aretightened after the concrete ispoured to strengthen the slab,helpingitresisttheforcesoftheexpansive soils. The slabs aresometimesthickened inplaces,often with beams running inboth directions on the under-sideoftheslab.Thesearecalledribbedfoundations.

The expansive soils below theslabareoftensaturatedduringconstructionbeforepouringtheslabsothesoilswillbeamaxi-mum height when the slab ispoured.

FROSTHEAVE– Ifthefootingsandfoundationsarenotdeepenough,thegroundbelowthemmayfreeze. FOOTINGSTOO Frozen ground expands and may pick up all or part 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.Thiscanleadtofrostheavingofthefootingsandthefoundations.


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A properly added exterior stairwell will include deepened foundations, or a completelyinsulatedapproach,topreventfrostpenetrationbelowthebuildingfootings.

IDENTIFYING Duringaninspection,theresultsoffootingfailurecanusuallybeseen.Itis,however,difficult THEPROBLEM toknowwhetherthebuildingisstillmoving,andifso,atwhatrate.Itisoftennecessaryto

monitorthebuildingoveraperiodofmonthsorevenyears,toknowwhethertheproblemwillwarrantrepair.Manyfootingfailuresarenotsevereenoughtowarrantrepairs.

REPAIRS– The usual corrective action is UNDERPINNING to underpin the footings. This

means digging under the exist-ing footing, and adding a newfooting wider and/or deeperthantheoriginal.Thismayhaveto be done in small sections onstrip footings since one cannotexcavateundertheentirehouseatonetime.Usuallytwotofourfootsectionsaredoneatatime.Thisisveryexpensivework.

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REPAIRS–PILES Insomecases,wherethesoils ANDHELICAL aremovingorarelikelytomove, ANCHORS underpinning is not appropri-

ate. Piles driven deep into theground are an alternative, butmay not be cost-effective foran existing building. Helicalanchorsaresometimesscrewedinto the soil to support failedfootings.

4.0Foundations

4.1General

Foundationstransmittheweightofthehousefromtheabove-gradewallsandfloorsdowntothefootings.Wherethereisabasementorcrawlspace,foundationsalsoresistthelateralpressureofthesoil.Thefoundationactsasaretainingwall inthissense. Incoldclimates,foundationscarrytheweightofthehousebelowthefrostlinetopreventfrostheaving.

Typicalfoundationmaterialsarestone,brick,pouredconcrete,concreteblock,cinderblock,insulatedconcreteforms,claytile,andwood.Mostofthesematerialsbehavesimilarly.Woodfoundationsaretheexception.


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COMMON Foundationsmaybecontinuouswalls(stemwalls),oftenmadeofconcrete,masonryblock FOUNDATION orinsulatedconcreteforms(ICF).Foundationsmayalsobepierssupportedbypadfootings. TYPES Wherefloodingisarisk,homesmaybebuiltonpiersthatarewellabovegrade.Piersmaybe

belowgrade,andmaybeconnectedbygradebeams.

Wheresoilconditionsarepoor,thebuildingmayrestonpilesthataredrivenorturneddownintothegroundtosomedepthtoprovideadequatebearingstrengthtosupportthehome.

Twocommonfoundationarrangementsareillustratedbelow.

CommonProblemswithFoundations

CRACKS/ Foundationwallsmaycrack,bow,spallorshift.Cracksmaybeduetoshrinkage,settlementor BOWING/ lateralforces.Somecracksareseriouswhileothersare insignificant.Bowing isusuallythe SPALLING resultoflateralforces.Spallingindicatespoorqualitymaterialsorchronicwaterproblems.

Someofthecausesoffoundationdefectsareoutlinedbelow.

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INADEQUATE Basement and crawlspace foundations are really retaining walls, holding back the soilLATERALSUPPORT outside.Ifthefoundationsdonotprovideenoughlateralsupport,theywilldeflectinwards.

This may be the result of mechanical forces exerted during back-filling; back-filling withfrozensoil(coldclimatesonly);unusualfrostdevelopmentinthesoilimmediatelyoutsidethebuilding (cold climates only); foundation walls that are too thin, too tall or do not haveadequatereinforcement;orthehousefloorsystemdoesnotprovideadequatebracingforthetopofthefoundationwall.Thislastproblemiscommononthehighsidewallonaslopinglot.Bothmasonrywallsandpouredconcretewallscanfailifnotproperlybuilt.

INWARD Foundationwalls thatmove inwardcanberepairedbytyingthembackfromtheoutside, BOWING usingtiesandanchors.Alternatively,buttressescanbeprovidedontheinterior.Theseoften

areconcreteorconcreteblockstructuresbuiltagainstthebasementwalls.Steelbeamsaresometimesused.Therearealsomodernstructuralfabricsthatcanbeappliedtostrengthenwalls. Another choice is to build a new foundation wall inside the old. In some cases thefoundationisreplaced.

BOWING/ Mechanicaldamagecausedwhenbackfillingduringconstructionforexample,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.Thestrengthofthefoundationisdeterminedbyitsmaterial–concreteorconcrete BACKFILL blockforexample,thestrengthoftheconcrete,thethicknessofthewall,whetherthewallis

laterallysupportedatthetop,andwhetherthewallisreinforced.

BOWING/ Theforceexertedby large tree rootsonthe foundationwall can leadtodeflectionof the CRACKS–TREE foundations.Somesoiltypesshrinkconsiderablyastheydryout.Ifalargetreedrawswater ROOTS fromsuchsoilsbelowafooting,

thefootingmaydropasthesoilcompacts. In this case, the treedamagesthehousewithoutac-tuallytouchingit.

Intheshortterm,treerootdam-age can be arrested by cuttingdown the tree and leaving theroots in place. Over the longterm,therootsmaybeexpectedtorot,leadingtosoilsettlement,resultant water leakage and,in some cases, building settle-ment.Therootsmayhavetoberemoved.

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/orasumpandpump, –GROUND areoftennecessary.Consultantsspecializinginsituationssuchastheseshouldbeengaged. WATER SeeSection10intheInteriorchapter.

SPALLING/ Low quality concrete subjected to damp soils may deteriorate, losing its 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 cold climates, if the foundations are too shallow, frost may heave even the best-built TOOSHALLOW footingsandfoundations.Onslopedlots,thepossibilityofshallowfoundationsisgreateston

thelowside.Propertieswithbasementwalk-outsareoftenvulnerabletofreezingdamage.

FROSTHEAVE– Conventionalcoldclimateconstructionassumesthehousewillbeheated.Anunheatedhouse UNHEATED may have frost penetrating through the basement floor below the footings, leading to HOUSES heaving.Thereisariskinvolvedinleavingahouseunheated.


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ADFREEZING Adfreezingisaphenomenon wherebydampsoilontheout-

side of the building actuallyfreezes to the building and asthe soil heaves, it will lift thetoppartofthefoundationwall.Horizontal cracks in founda-tionwallsjustbelowgradearetypical.

4.2WoodFoundations

Preservedwoodfoundationswereintroducedintheearly1960s.Severalthousandunitshavebeeninstalled.Lifeexpectanciesofthebelow-groundwoodareestimatedinthe50to100year range, considerably less than many traditional building foundation materials. Somemanufacturersoffer60yearlimitedwarranties.

Thewoodischemicallytreatedto retard rot. Chemical treat-mentforwoodusedinfounda-tionsismoreintensivethanthattypicallyusedinwoodfordecks,fencing,etc.Thewoodfounda-tions may rest on concrete orwood footings. With woodfoundations, special care mustbe taken to ensure that thefoundation is able to performitsretainingwallfunction(ade-quatelyresistinglateralforces).

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CommonProblemswithWoodFoundations

ROT/INSECT Rotandinsectdamagearethemajorenemiesofwoodfoundations.Woodfoundationsshould DAMAGE notbeusedinareaspronetowood-destroyinginsectssuchastermites.

4.3PileFoundations

Pilesaresteel,woodorconcretecolumnsdrivenintothesoil.Theyareusedinweaksoilsandmayextenddownthroughthepoorsoil,toreachasoilwithgoodbearingstrength.Pilesmaydependonfrictionbetweenthesidesofthepileandthesoilfortheirsupport.Theymayalsobepoint bearing at the bottom.The building itself rests onbeamsorwallsthatstraddlethepiles. Piles are expensive andoncethebuildingisup,thereisoften no way to know if pileshave been used and where.Again, thepresenceorabsenceof building settlement is theonlywaytodeterminehowsuc-cessfultheapproachhasbeen.

PILESAND Insomeareas,garagesaretypicallyconstructedonpiles.Thepilessupportpouredconcrete GRADEBEAMS gradebeamsforexample,whichinturn,supportthefloorandwallsystems.Thegaragefloor

isthenpouredontheundisturbedsoil.

4.4PierFoundations

Wherecontinuousfoundationsarenotprovided,individualcolumnsor“piers”maybeusedtosupportabuilding.Thepiersshouldrestonafootingbelowthefrostlineincoldclimatesandtypicallythepiersupportsabeam.Thebeam,inturn,supportsthefloor,wallandroofloads.

Piers are commonly found in houses where there is no basement or a partial basement.A crawlspace often has a pier system supporting the structure above. Porches are alsocommonlysupportedbypiers.


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Piersmaybestone,brick,con-crete block, cinder block, orwood. Most of these materi-als behave in a similar fashion.Wood, of course, is the mostvulnerable to rot and insectdamage. As a rule, wood/soilcontactisbestavoided.

Concrete piers are often usedwith grade beams where ex-pansivesoilsareanissue.

CommonProblemswithPiers

SETTLEMENT– Pierproblemsareoftentheresultofinadequatefootings.Thiswillresultinsettlementofthe INADEQUATE pierand,ofcourse,thebuildingabove.Ifthepierbaseisnotbelowthefrostlineinnorthern FOOTINGS climates,frostheavingcanbeaproblem. Inboththesecases,thepiersusuallyhavetobe

rebuilt.Similarproblemscanresultinareaswithexpansivesoils.

OVERSPANNED If thepiershavetoogreataspanbetweenthem,thebeamsmaysagortheconcentratedloadsmaycausethepierstosink.Addingpiersisthetypicalsolutionhere.

TOOSLENDER If thepiersaretooslenderorareoutofplumb,theymaynotbecapableofcarryingtheir OROUTOF intendedloads.Diagonalwoodbracesareusedinsomeareastohelpholdpiersinplace.Piers PLUMB that are deteriorated as a result of moisture or mechanical damage should be repaired or

replacedasnecessary.

Woodpierscanrot,beattackedbywood-boringinsects,fireorbedamagedmechanically.

SKIRTING Preservedwoodperformsbetterthanmostspeciesofuntreatedwood.Wherepiersareusedinlieuofacontinuousfoundation,thespacebetweenthepiersusuallyhastobefilledintopreventsoilfromfallingintothebasementorcrawlspace.Inabove-gradesituations,skirtingkeepsoutanimalsand,tosomeextent,rain,snowandcold.Skirtingmaybewood,masonryorpouredconcrete,forexample.Wheretheskirtingisnotstructural,repairstodeterioratedskirtingareoftendeferred.Woodskirtingoftendeteriorateswhereitcontactsthesoil.

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5.0 Floors

Floorsprovidethebearingsurfaceforpeopleandfurniture.Theyalsotiethebuildingtogether,addingrigidityandprovidingasurfaceforfloorcoveringsaboveandceilingfinishesbelow.Wewilllookatfloorcomponentsoneatatime.

5.1Sills

Woodsillsprovidealevel,continuouspadbetweenthefoundationtopandthebottomoftheframingsystem.Thesillssecurethefloorsystemtothefoundation.

ANCHOREDTO Typically,thefloorjoistsrestdirectlyonandaresecuredtothesill.Sillsshouldbeanchored FOUNDATION tothefoundation.Thisisoftenaccomplishedusingboltsanchoredintothetopofthefounda-

tionwall,passingthroughthesillandsecuredwithawasherandnut.

In new construction, the sill istypicallyawoodframingmem-ber(2x4or2x6)laidflat.Inolderconstruction it may be a sub-stantial wood beam (e.g. 8x8).Wood sills can support woodframing members but shouldnot support brick or stone.

CommonProblemswithSills

CRUSHED– Sills may be crushed as a result of concentrated loads. Steel posts built into walls will CONCENTRATED sometimescausethis. LOADS

CRUSHED– Ifthebeamsorjoistsaretooshort,andonlytheveryendrestsonthesill(lessthanoneinch, INADEQUATE forexample),theconcentratedloadsmaycrushthesill. ENDBEARING

MOVEMENT– Wherethesillsarenotsecuredtothefoundations,thereisdangerofthebuildingshifting INADEQUATE duringhighwinds,whensignificantupwardsandlateralforcescanbegenerated. ANCHORING


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ROT/INSECT Woodsillsclosetogradelevelaresubjecttorotandinsectattackbecausetheyarewetmuch DAMAGE ofthetime.Soilistypicallydamp.Sillsmayrotandcrushundertheweightoftheframing

system.Thiswillweakenthestructure,allowingittosettleslightlyandbreaktheconnectionbetweenthefloorandfoundation.

5.2Beams

Beams carry floor and wall loads horizontally to the foundations, walls, columns or posts.Beamsmaybewood(solid,built-uporengineered),plywoodorsteel.

CommonProblemswithBeams

SAG– Undersizedoroverspannedbeamsmaysagorcrack.Thismay leadtofailureof theentire OVERSPANNED framingsystem.Fortunately,thisrarelyhappens,andalmostneversuddenly.Overspanned

woodbeamscanusuallybeidentifiedreadily,andpostscanbeaddedorthebeamcanbestrengthened.

CRUSH/FALL– Wheretheendbearingisinadequate,thebeamcancrushitselforitssupport.Thereisalso ENDBEARING potentialforthebeamtoslipoffitssupport.Typically,threeinchesisconsideredaminimum

endbearingforbeamswhensupportedbymasonryorconcrete.

ROT/INSECT Wood building components are vulnerable to rot, damage, insect attack and fire. Rot and DAMAGE insectdamagearecommonwherethere iswood/soil contact. 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 is

relatively uncommon but canlead to damage and ultimatefailure.

NAILINGAND Built-up wood beams may not BUTTJOINTS beadequatelynailed.Normally,

nailsshouldbeprovidedindou-ble rows every 18 inches alongthebeam.Wherebuttjointsoc-curinwoodbeams,theyshouldbe located over the supportsor as follows: the butt jointsshouldbewithinsixinchesofthequarterpointofthespan.Forexample,ifthespanis12feet,thejointshouldbewithinsixinchesofthethree-footmarkorthenine-footmarkofthespan;(i.e.thejointsshouldbe2-1/2to3-1/2feetfromtheendsupports).

RUST Steel beams are susceptible to rust, particularly if the basement is damp. Steel should bepaintedtopreventrust.Lateralsupportforsteelbeamsistypicallyprovidedbywoodstrap-pingsecuredtothejoists.

LATERAL Lateralsupportforsteelbeamsistypicallyprovidedbywoodstrappingsecuredtothejoists. SUPPORT Thereareseveralwaystoprovidelateralsupportforwoodbeams.Seetheillustrationbelow.


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SECURINGTO Steelbeamsmaybepoorlysecuredtoposts.Windupliftmaycausethebeamtoliftoffthe POSTS post,orimpactmayshiftitsothatsupportisnolongeroffered.Thebeamandpostshouldbe

bolted,weldedorclippedtogeth-er. In hurricane or earthquakeareas, additional fastening maybe necessary. Special straps areusedtoaccomplishthis.

STRENGTH A visual inspection of a steelbeam cannot determine itsstrengthbecauseitdependsonmorethansize.Theshapeofthebeam,thelengthandthicknessof both the flanges and web,and the weight per linear foot,all influence beam strength.Thecarboncontentofsteelalsoaffectsitsperformance.

STEELVERSUS Steelbeamscanbemuchstrongerthanwoodbeamsandaremoreresistanttorot,insectand WOOD mechanical damage, but are more expensive, heavier, and more difficult to work with.

Engineeredwoodbeamscanbestrongerthansolidwood,yetarelight,easytoworkwithandlessexpensivethansteel.Woodbeamscanbecutonsitemoreeasilythansteel.Steelbeamsshouldrestonsteelpostsormasonry.Woodbeamscanrestonwoodmembers.

FIRE Fire isaconcernwithbothwoodandsteelbeams. Interestingly,asteelbeamwill lose itsstrengthmuchearlierinafirethanawoodbeam,althoughawoodbeamburnsandasteelbeamdoesnot.Steellosesitsstrengthafterbeingexposedtotemperaturesof1000°F.foraboutfourminutes.Steelbeamssaglikespaghettiduringafire,allowingbuildingstocollapsequickly.Woodburnsbutlosesitsstrengthmuchmoreslowly.

5.3PostsandColumns

Posts or columns (two namesfor the same thing) carry theload of the beam verticallydowntothefootings.Theymaybebrick,concreteblock,pouredconcrete,wood,orsteel.

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CommonProblemswithPostsandColumns

SPALLING/ Masonrypostsmaybedeterioratedasaresultofmoistureorpoormortar.Risingdampisa MORTAR common problem with brick columns. This is characterized by deteriorated mortar and DETERIORATION efflorescence(whitesaltydeposits)onthebottomofthepost.Insomecases,thebrickitself

deteriorates(spalls).

OUTOFPLUMB Posts that are out of plumb lose a good deal of their strength. Generally speaking, if thecolumnisoutofplumbbyroughlyone-thirdofitsthickness,theremaybeconcernaboutitsintegrity.

RUST Rustonsteelpostscanbeaconcern.Thisisoftenaseriousproblematthebottomofthepostinachronicallyfloodingbasement.Rustwillquicklyreducetheloadcarryingcapacityofasteelpost.

ROT/INSECT Wood posts are vulnerable to rot and insect attack. This is especially true where the post DAMAGE penetratesthebasementfloorslab.Correctiveactionoftenincludessimplycuttingoffthe

bottomofthepostandplacingitonaconcretepad.

FOOTING– A sinking post is usually the result of a missing or inadequately sized footing. Obviously, MISSINGORTOO suitablefootingsshouldbeprovided.Everypostorcolumnshouldhaveafooting.Thesecan’t SMALL typicallybeseenoncethehomeisbuilt.

UNDERSIZEDOR Columncollapseissomewhatunusualbutisnormallytheresultofanundersizedcolumnor DAMAGED onethathassufferedmechanicaldamage.

NOTWELL Apostthatisnotwellsecuredtothebeamabovecanallowthehousetoshiftduringwind SECUREDTO upliftforces.Thebeamshouldalsobesupportedlaterallytopreventitfrommovingsideways. BEAM SeeSection5.2.


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5.4FloorJoistsandTrusses

Thefunctionoftheseframingmembersistocarryandtransferloadsfromthefloorstothefoundations,beamsorbearingwalls.

5.4.1ConventionalWoodJoists:Joistsaretraditionaldimensionallumber,typically2x8,2x10,or2x12.Thesehorizontalmemberscanbe12to24inchesapart,although16inchesisthemostcommon.Theyarelaidonedgesothatthesubflooringisnailedtothetwo-inchside.Floorjoistsshould extend at least 1-1/2inches onto the foundation orbeamateitherend.

JOISTSTRENGTH The strength of a joist comeslargelyfromitsdepth.Doublingajoistbyputtinganotherofthesame size beside it will doubleits resistance to bending.Doubling the depth of a joistincreasesitsresistancetobend-ingbyeighttimes!Forexample,the equivalent strength (con-sideringdeflectiononly)oftwo2x10s compared to four 2x8scanbecomparedbymultiplyingthebasetimestheheightcubed.Itisinterestingthattwo2x10saremoreresistanttobendingthanfour2x8s.

Thedeflectionofafloorandjoistsysteminmodernconstructionmaybequitesurprising.Manycodesallowafloortodeflect1/360thofitslengthundernormalloadingifthereisafinishedceilingbelow.Forexample,thefollowingsituationisacceptablebymanycodes:2x10floorjoistsspaced16inchesoncenterspanabout15feet.Whentheroomisoccupiedwithfurnitureandpeople,thecenterpartofthefloorcanbe1/2inchlowerthantheflooredges.Thisiscompletelysafe,andthefloorisnotatriskoffailing.However,thismaynotbesatisfac-torytosomehomeowners.Codesareaminimumstandard.Brittlefloorfinishingmaterialslikeceramictilemaynottolerateaflexlikethis.Morerigidfloorsareoftenusedwheretheflooringmaterialisbrittle.

SPRINGYOR Floors are often bouncy or springy when people walk across a room, but this is not BOUNCYFLOORS necessarilyindicativeofproblems.Lightframingcausesthiscondition,andwhilethefloorcan

bestiffened,thisisrarelydone.

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CommonProblemswithConventionalWoodJoists

OVERSPANNED Floorjoiststhatareoverspanned(undersized)arepronetosagging.Theacceptablespanofajoistisdeterminedbytheloaditwillcarry,thespeciesandgradeoflumberused,thedepthof the joist, and the spacingbetween joists. Over spanningcanbereadilycorrectedbyadd-ing joists, or adding a beambelow the joists in most cases.The implication of over span-ning is typically a noticeablesag,andinsomecases,abouncyfloorsystem.

DAMAGE/ Mechanical damage to joists is NOTCHED/ common. Joists are commonly DRILLED notched,drilledandcutthrough

toaccommodateheating,plum-bing and electrical systems. Insomecases,joistsarecutaroundstairwells to improve head-room. Some damage is typical,andthereareseveralguidelinesonacceptablelimits.Joistsaresometimesnotchedattheendtorestonabeamorfoundationwall.Thiscanweakenthejoistconsiderably.Thejoistusuallycrackshorizontallyfromthetopofthenotchtowardsthemid-pointofthespan.

INADEQUATE Joistsmaybepronetocrushingattheendsand/orslippingoffthebeamorfoundationwhere ENDBEARING thereislessthan1-1/2inchofendbearing.


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JOISTHANGER Metalbracketscalled“joisthangers”areusedwherejoistscannotrestonasupport.Here,the PROBLEM joistsarecradledinandnailedtothehangers,whicharesecuredtothesideofabeamor

header.Joisthangersmaybeundersizedorinadequatelynailed.

ROT/INSECT Rotandinsectscanattackanywoodcomponents.Joistendsclosetooutsidewallsarevulner- DAMAGE able,especiallyiftheoutsidesoillevelisashighasthejoists.

SAG– Mostfloorsaredesignedtocarryliveloadsof30to40poundspersquarefoot(psf).Larger CONCENTRATED loads can lead to sagging and ultimately, failure. Special consideration may be neededfor LOADS pianos,waterbeds,aquariums,andfloor-to-ceilingbookstorage,forexample.

SAG–JOISTS Joists that see concentrated BELOWWALLS loadsaremorepronetosagging.

Ajoistbelowanon-bearingwallshould be strengthened, oftenbydoublingit.Joistsshouldnotbe used below load-bearingwalls. Beams or bearing wallsshouldbeusedhere.

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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 supportingthefirstfloor.Thereisoftenabearingwallabove,supportingthesecondflooror

roofstructure.Ideally,thefirstfloorwallisdirectlyoverthebeamorwallbelow.Ifthewallis offset enough (sometimes 12 inches is enough), the joists will sag under the first floorwallabove.Thiswill leadtoa lowspot inthefloorwherethewallsitsandahumpinthefloorabovethebeamorbearingwallbelow.Thissortofmovementisrarelydangerousbutitdoesmakesomepeopleuncomfortable.

5.4.2EngineeredWoodJoists:Engineeredjoistsmayhaveconventionallumbertopandbot-tomplates,orthetopandbottomplates(flanges)maybeLVLs(LaminatedVeneerLumber),PSLs (Parallel Strand Lumber), or LSLs (Laminated Strand Lumber). Webs may be plywood,orientedstrandboard(OSB)ormetal.

LVLs,PSLs,andLSLscanalsobeusedasjoists,beams,sills,lintels,columns,studs,rafters,etc.Glulams(gluelaminatedlumber),madeupofconventionallumberpiecesgluedtogether,canalsobeusedformanywoodstructuralmembers.

These systems have much longer spans than conventional lumber, and are less prone toshrinkageandwarpingproblemsthanconventionallumber.Therulesforengineeredwoodaredifferentthanforconventionaljoists,andsomeoftherulesarespecifictoindividualman-ufacturers.Asalways,ahomeinspectionisavisualevaluationoffieldperformanceratherthanadesignanalysis.

ProblemsSpecifictoEngineeredWoodJoists

DAMAGE Mechanicaldamageiscommon.Joistsarenotched,drilledandevencutthroughtoaccommo-dateheating,plumbingandelectricalsystems.Insomecases,joistsarecutaroundstairwellstoimproveheadroom.Holesmaybetoobigorinthewrongplace(manysystemshaveknock-outsthatindicatewheretheholesmustbe).Split,notchedorcutflangesmaybeaproblem.ThetopandbottomflangesofwoodI-joists(asengineeredwoodjoistsareoftencalled)andtrussesarecritical.Anyweakeningwillseriouslyaffectthestrengthofthesystem.

INADEQUATE Inadequate end bearing is a problem. More end bearing than conventional joists is often ENDBEARING required.1-3/4inchesisacommonminimum.

JOISTHANGER Metalhangerscalled“joisthangers”areusedwherejoistscannotrestonasupport.Here,the PROBLEMS joistssitinthehangers,whicharesecuredtothesideofabeamorheader.Joisthangersmay

betooshort,toowide,thewrongtype,andmaynothaveenoughnailsormayhavethewrongkindofnails.

RIMJOISTISSUES Properrimjoistmaterialmaynotbeused.Engineeredwoodmayrequire3/4-inchplywoodorspecialrimjoistmaterials.Rimsshouldnotbeconventionallumber.Inadequateloadtransferthroughrimjoistsisacommonproblem.

SQUASHBLOCKS Blocking(squashblocksorwebstiffeners)maybemissingor incompletewhere joistsrest MISSING/ onbeamsorwhereloadsfrombearingwallsabovearetransmitteddownthroughengineered INCOMPLETE woodjoiststobeamsorsills.


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BRIDGING Inadequate bridging or load sharing can be a problem. Different systems have different MISSING/ requirementsforbridging. INEFFECTIVE

5.4.3FloorTrusses:Thetopandbottomhorizontalmembersarecalled“chords”.Theshorterinteriorpiecesarereferredtoas“webs”.Theyaremadefromwood,steeland/orplywood.Trussescanspangreaterdistancesthanconventionalwoodjoists.Beamsandpostsorbear-ingwallscanbeomittedorremovedwiththeuseoffloortrusses.Thesesystemsalsoallowheating,plumbingandelectricalsystemstorunthroughthetrusses,leavingmoreheadroombelow.Trussesdonotnormallyrequirebridgingorbracing.

Trussesaredeeperthanjoistsandcanrestrictheadroominsomecases.Asageneralguide,thetrussdepthis1/12to1/20ofitsspan.Mosttrussesare10to18inchesdeep.

CommonProblemswithFloorTrusses

UPSIDEDOWN Many trusses have a top and a bottom, and must be installed in the correct orientation.Atrussinstalledupsidedownisconsiderablyweakened.

CUT Trussescannotbecutaroundopenings,thewayjoistscan.Conventionaljoistscanbefieldcuttoappropriatelengths.Atrusscannotbecut.Allodd-lengthtrussesmustbeengineered.Siteconditionsthatarenotforeseenorlastminuteplanchanges,canleadtowastedmoneyanddelays,whenworkingwithfloortrusses.

SPAN Trussesmaybeoverspannedjustlikejoists.Theseengineeredsystemscanonlybeevaluatedinthefieldbytheirperformance.Homeinspectorsdonotreviewthedesignofengineeredsystemsliketrusses.

DAMAGE/ROT/ Woodfloortrussesarevulnerabletomechanicalabuse,rotandinsects. INSECTS

5.4.4HeadersandTrimmers:Headersandtrimmersstrengthenanopeninginthefloorjoistpatternforastairwellorchimney.Also,basementwindowsoftenpreventfloorjoistsfromrestingonthefoundationwallsandtheseopeningsintheframingpatternmustbestrength-ened.

Normally,joiststhatcannotrestonawallorbeamaresecuredtoa header. A header is typicallymade of the same size lumberas the joists (e.g. 2x8s). Theheader,whichrunsperpendicu-lartothejoists,carriestheloadfromtheshortjoists(tailjoists)overtotrimmerjoists.Trimmerjoists are the joists on eithersideoftheopeningthatrunfulllength.

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POSTS Postscanbeprovidedatthecornersoftheopeningtocarryloadfromtheheaderdirectlydown to thefloor. In this case, the trimmers could remainsingle. The headercanalso besupportedwithabearingwallrunningundertheheader.

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. Headers may also be inadequately secured to the

trimmers.Again,joisthangerscanbeused.

ROT/INSECT Rotandinsectscanweakenthe DAMAGE stairwellopeningframing.

5.4.5BridgingandBlocking(andStrapping): Bridging/blockingpreventthejoistsfromtwisting.Diagonalbridging isusually2x2woodblocksormetalstrapping.Solidblockingisthesamesizeasthe joists. To be effective, thebridgingorblockingshouldbeinastraightlineandshouldextendthefulllengthofthefloor.

Solidblockingisrequiredattheends of joists. Tall joists requirebridging or blocking at leastevery eight feet. More blockingmay be needed where earth-quakesarearisk.

5.4.6 Cantilevers: Floor joistsmaybecantilevered (extended)slightly beyond their supports.Acommonexampleisabalcony.This is often done on an upperfloor,wheresupportpostswouldbeexpensiveandunsightly.Theprinciple is that since wood isrelativelystiff,ifpartofajoistiswellsecuredatoneendandpartway along its length, the otherendcanbeunsupported.Rough-ly1/6ofthejoistspanbetweensupportscanbeusuallybecantileveredsafelybeyondasupport.


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CommonProblemswithCantilevers

OVERSPANNED Where the joists are cantilevered too far, the deck or balcony will be weak. This is usuallydetectablebythespringinessofthestructurewhenwalkingonit.Inseverecases,failureispossible.Postsorbracescanbeaddedbelowthedeck.

WATER Since the joists penetrate the building wall, there is the possibility of leakage into the PROBLEMS wallsordirectlyintothehomeattheconnectionpoints.Thejointsbetweenthejoistsand

thewallmustbekeptwellsealed.Thisisacommonspotforrottodevelop,attackingboththecantileveredjoistsandthewallstructure.

ROT/INSECT Cantileveredwoodstructuresaresusceptibletorotandinsectdamage. DAMAGE

5.4.7 Steel Floor Framing: Structural framing elements are generally either C-shaped orU-shapedsteelcomponents.C-shapedelementsaredesignedasload-bearingelements,suchasjoists,whiletheU-shapedpiecesaretracks,orchannels,designedtoholdtheload-bearingcomponentsinplace.

Steelframingmembersarenormallyscrewedtogether,althoughtheymayalsobewelded.Membersmaybescreweddirectly toeachother,orclips (clipangles)maybeusedto joinmemberstogether,withtheclipbeingscrewedtobothelements.Screwsarealsousedtojoin wood framing, sheathing,and drywall finished to steelframing. Securing joists tosteelbeamsrequirestheuseofclips and powder-actuated fas-tenerguns.

BEARING Bearingstiffeners(webstiffen- STIFFENERS ers) are required where a con-

centrated load, such as a doorjamb,restsonafloorjoist.Theseusually take the form of asectionofstudortrackmountedvertically on either side of thejoistbelowthepointload.Webstiffeners are also requiredwhere the joist rests on a loadbearingbeamorwall.

HOLES/NOTCHES Steelfloorjoistsusuallycomewithpre-punchedholesforplumbingandelectricalwiring,andshouldbeinstalledsothattheseholesarealignedforeasyinstallationofthemechanicalandelectrical systems.Thereare industry-specified requirements forotherholes. Joists shouldnotbenotched.

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BRIDGING/ Floorjoistswilltwistandbounceunderloadifthetopsandbottomsarenotproperlybraced. BLOCKING Thetopistypicallybracedbytheflooring.Thebottomscanbebracedwithadrywallceiling

forexample.Wherethereisnoceiling,thejoistbottomsshouldbebracedevery12feet.ThiscanbeX-bracing,flatstrapsalongtheundersidesand/orsolidblocking.

FRAMING Whenthejoistpatternisinterruptedbyopeningsforstairwellsandchimneysforexample, AROUNDSTAIRS reinforcingwithheadersandtrimmersisrequired,inmuchthesamewayitisdonewithwood ANDCHIMNEYS framing.

CommonProblemswithSteelFloorFraming

RUST/ Steelframingmembersincontactwithmoistureforaprolongedperiodoftimewillcorrode. CORROSION Thismaybeanissueinbelow-gradeareasorbelowrooforplumbingleaks.

OVERSPANNED Thespanofasteelfloorjoistdependsonitsheight,widthandthegaugeofsteelused.Whiletherearegeneralguidelines,individualmanufacturershavespecificrequirements.

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-flooring(AlsocalledFloorSheathing)

Sub-flooringtransmitsthe live loadsofthepeopleandfurnishingstothefloor joists.Sub-flooringmaybecoveredwithafinishflooringmaterialormayserveasafinishflooringitself.

One-inchthickwoodboardswereusedassub-flooringuntilroughlythe1960s.Morerecently,plywoodandwaferboardhavebeenused.Thinconcretesubfloorsarelesscommon.


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CommonProblemswithSub-flooring

SPRINGYFLOORS Subflooring that is too thin will be springy and may fail under concentrated loads (e.g. apiano).Thisshouldbeoverlaidtoprovideastiffersubfloor.

SQUEAKY Subflooring not adequately secured to the floor joists may be squeaky. The weight of FLOORS someonewalkingonafloorwilltemporarilypushthesubfloordownontothejoist.When

thefootisremoved,thesubfloorwillliftoffslightlyagain.Thenoiseisthenailssqueakingastheyslideinandout,orpiecesofwoodrubbingagainsteachother.Solutionstothisnuisanceincludere-nailing,screwingandgluingthesubfloortothejoists.

WATERDAMAGE Waferboard subflooring can be damaged by relatively small amounts of water. The boardtendstoswell,resultinginfloorunevenness.Theswellingalsopullsthenailsoutofthejoistsorthroughthewaferboard.Ultimately,theboardcanloseitsstrength.

EDGESUPPORT Diagonalplanksubflooringmustbesupportedwhereitmeetsthewall.Theendsofsomeoftheplanksmaybeseveralinchesfromafloorjoistandifadequateblockingisnotprovided,the floor will be weak in thisarea.Whereplywoodorwafer-boardsubflooringsheetsmeet,thejointshouldbesupportedbyjoists, blocking or tongue-and-groove connections betweenthesheets.

DAMAGE Any subflooring can be me-chanicallydamagedand,unlessrepairs are made, this can leadto an unsafe situation. A com-monproblemisaholecutforaheatingregisterthatwasneverinstalled. If carpet is laid, thismaynotbenoticeduntilafurni-turelegisputontheweakspot.Repairs are, of course, simpleandinexpensive.

UNEVEN Uneven subflooring can be a nuisance. Uneven joist installation is a common cause, as isdebrisonthetopofthejoistswhenthesubfloorislaid.Swollenwaferboardordelaminatedplywoodcanalsoresultinunevenness.Carelessjoiningoftongue-and-groovesheetscanleadtosurfaceirregularity.

ROT/INSECT Subflooringissusceptibletorotandinsectdamage. DAMAGE

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5.6ConcreteFloors

Concretefloorsinhomeswithbasementsareusuallynotstructural.Basementandgaragefloorslabsrestonthegroundandareusuallypouredafterthehouseisbuilt.Modernfloorsaretypicallythree-inchthickslabs,althougholdonesmaybeasthinas1/2inch.

Slab-on-gradehomesmayhaveconcretefloorsthatarepartofthestructure.

CommonProblemswithConcreteFloors

CRACKED/ Floorsmaybecrackedorbroken.Replacementisnotapriority,butisoftendonetomakea BROKEN basementorgaragemoreusable.Brokenutilitylinesareapossibilitywithslabmovementon

slab-on-gradehomes.Themovementmaybesettlementorheavingduetoexpansivesoils,forexample.

NOSLOPETO Manybasementandgarageslabsdonotslopetodrains.Re-slopingisrarelydonebecauseit DRAIN isexpensiveandtheproblemofwateronafloorisrarelyserious.

SUSPENDED Suspendedconcretefloorsarenotcommoninhomes.Oneexceptionisconcreteporchslabs SLABS abovecoldcellars.

Suspendedconcretefloorsabovegradearecommoninhigh-riseandcommercialbuildings,andusesteelreinforcing.Theyareheavierandmoreexpensivethanconventionalwoodfloors,butcanalsobestrongerandaremorefireresistant.Suspendedconcretefloorsystemsarenotevaluatedduringahomeinspection.

6.0WallSystems

Wallscarrytheweightoftheroofandfloorsdowntothefoundations,aswellasprovidingaseparationbetweeninsideandoutside.Wallskeepoutthewind,rain,heat,cold,andnoise,aswellasprovidinguswithprivacyandsupportforinteriorandexteriorfinishes.

Afterahomeisbuilt,itmaybedifficulttoidentifythewallconstruction.

6.1Materials

6.1.1 Masonry Walls: Common materials include brick, stone, concrete block, cinder block,claytileandglassblock.Masonrywallsaretypicallycomprisedoftwofour-inchthickwythes(layers) of masonry. The outer wythe is often weather-resistant brick or stone. The innerwythe(layer)maybelowerqualitybrick,concreteblockorcinderblock.Thefoundationmustbewideenoughtocarrybothlayersofmasonry.

Mortarusedtobindmasonryunitstogetherisacombinationofcement,sand,andwater.Formoreinformationonbrickandmortar,seeSection3.2intheExteriorchapter.

Themasonryunitsmaybeexposedorcoveredwithstucco,forexample.


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IDENTIFICATION Inmostcases,asolidmasonrywallcanbeidentifiedbytheheadercourses(rowswherethebrickisturnedend-wisetolocktheinnerandouterwythesofthewalltogether).Thisisdoneeveryfivetosevencourses(rows)upthewall.Sometimeseverybrickinthecourseisturnedend-wise.Often,onlyeveryotherbrickisturned,andsometimesthepatternisrandom.Inmostcases,however,thereareatleastsomeoftheunitsthatareturnedineveryfifth,sixthorseventhcourse.

Metal tiesorspeciallysizedbrickscanalsobeusedto jointhe innerandouterwythes. Inthiscasethewallwillshownoheadercourses,anditwillnotbeapparentthatitisasolidmasonrywall.

Solidmasonrywallshavenotbeencommonlyusedonsingle-familyhomes inmanyareassincetheearly1970s.Areaspronetohurricanesareanexception.

CommonProblemswithMasonryWalls

DETERIORATED Thewallmaybeweakenedifthemasonryorthemortardeteriorates.Thismaybetheresultofpoorqualitymasonryormortar,chronicmoistureexposureorfreezing.

CRACKS Cracksinbrickworkmayappearforseveralreasons.Cracksareclues,andtheirsize,location,direction and rate of growth are all indicators of what is happening. Generally speaking,cracksthroughmortarjointsarelessseriousthancracksthroughthebrickorblock,butthereareexceptions.

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LEAN/BOW Wheretheinnerandouterwythesarenotadequatelysecuredtogether,theouterwythescanleanorbowoutwards.Theentirebrickwallmayleanorbowduetofoundationsettlementorthe wall not having adequate lateral support. Walls may also be pushed out of plumb byvehicleimpact,forexample.Ifawallleans,theultimatedangeristhatitmayfall.Themoreimmediatedanger,however,isthattheraftersandjoistsrestingonthewallmayslipoffasthewallmovesoutawayfromthebuilding.Sincetheendsofjoistsmayonlyrestonthewallbyaninchortwo,alittlemovementcancreateanunsafesituation.Ifjoistsorraftersslipofftheirsupports,theframingsystemwillcollapse.

RAFTERSPREAD Spreadingroofraftersmaypushthetopofthewallsout,result-inginanunstablesituation.


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EXCESS Brickcanbecorbelled(offset) CORBELLING onlyaboutoneinchbeyondthe

brick below (i.e. one brick doesnothavetobesetexactlyontopofanother).However,thetotalcorbellingmustnotexceedone-third of the wall thickness tomaintainstability.

6.1.2 Wood Frame Walls: Load-bearingwoodframewallsmaybeinteriororexteriorwalls.

Some stud walls are load-bearing,othersarenot.Bearingwallsshouldhaveadoubletopplate. Non-bearing stud wallsmayhaveonlyasingletopplate.Asinglesoleplate(alsocalledsillplateorbottomplate)isprovidedineithercase.Noneofthisisvisibleoncethehomeisfinished.

Historically,2x4studshavebeenused,spaced16inchesoncenter,althoughmorerecently,2x6 exterior wall studs have become common as they provide more space for insulationbetweenthestuds.

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CommonProblemswithWoodFrameWalls

Rot, insect attack, mechanical damage, poor quality lumber, poor connections, designmistakes,poorworkmanshipandexcessivespacingcanallbeproblems.

POORNAILING Inadequate nailing can lead to ANDOPENING difficulties. Openings in walls

maynotbeadequatelyframed.Wall sections above largeopenings for picture windows,for example, may sag if theopenings are not bridged withappropriate support headers(somecalltheselintels).

NOTCHES Holes and notches can weaken ANDHOLES studs if they are too large. The

illustrations below providesomeguidelines.

BUCKLING Somewoodstudwallsaresusceptibletobucklingunderloads.Thisisparticularlytrueifthewallsarenotbracedwithgirts(blockingbetweenstudsnearthemid-point)orifinteriororexteriorfinishesarenotprovided.Iffinishisprovidedononesideofthewall,girtsarenotrequired.

Longerstudsaremoresusceptibletobuckling.Thisiseasytounderstandifyouholdbothendsofayardstickandtryandpushtheendstowardeachother.Theyardstickbucklesveryeasilyinthemiddle.Thisismoredifficultwithasix-inchrulerofthesamematerial.

Whereanotherfloorlevelistobeaddedtoahome,specialconsiderationshouldbegiventostudwalls,whichmaynotbestrongenoughtocarrytheaddedweight.


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CONDENSATION Rotormoldcausedbycondensationinexteriorwallsisaconcern,especiallywhereinsulation INCOLD isupgradedinolderhouses,andwithouteffectiveair/vaporbarriers.Thiscannotbedetected CLIMATES duringavisualinspectionanditmaybealongtimebeforethedamageisnoticed.Insome

cases,peelingexteriorpaintsuggeststhatwallcondensationisaproblem.

Thisistypicallyaseasonalproblemincoldclimates,withthecondensationoccurringduringthewintermonthsonly.Warmmoistairentersthewallfromthehouse.Asitpassesthrough,the air cools. Cool air cannot hold as much water vapor as warm air. Condensation formsinsidethewallastheaircoolsandgivesoffitswater.

LOWQUALITY Poorqualitystudsorstudsthatwarpandbowcanleadtounevenwallsurfacesinnewhomes. LUMBER Thebowedortwistedstudshavetoberepairedorreplaced.

GREENLUMBER Buildingwithlumberthatistoowetor“green”canresultinproblemssuchasshrinking,warp-ing,orbowing.

6.1.2.1BalloonFraming:Balloonframingwascommoninthelate19thandearly20thcentu-ries. This wood-frame construction technique used conventional studs and floor joists.

However,thewallstudswerecontinuousfromthefoundation up to the roof line. The constructionprocess involves setting up the wall studs, andthenhangingthefloorsystemsfromthem.Whencompleted, this resulted in a rigid structure. Onedisadvantage is thatafirecanmoveveryquicklyupthroughthecontinuousstudspaces.

6.1.2.2 Platform Framing: Platform or Westernframingisslightlydifferent.Awoodfloorjoistandsubfloorsystemisprovidedontopofthefounda-tions.One-storystudwallsarebuiltonthefloor.Ifthehouseistwostories,asecondfloorplatformisassembledontopofthestuds,andthenasecondstudwall isbuiltontopofthisplatform.Thiscanbeextendeduptoformathree-storyhouseaswell.The advantages of platform framing are ease ofinstallationandlowermaterialcosts.

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6.1.3 Steel Frame: Steel frame walls may be load-bearing, carrying the weight of the roofandfloorsdowntothefoundations.Theymaybeinteriororexteriorwalls.Steelframewallsmayalsobeusedasnon-load-bearingpartitionwalls.Whilewoodframingmembershavetraditionally dominated residential construction, the use of lightweight steel framing isincreasing.

StructuralframingelementsaregenerallyeitherC-shapedorU-shaped.C-shapedelementsaredesignedasload-bearingelements,suchasstudsandjoists,whiletheU-shapedpiecesaretracks, or channels that hold the load-bearing components in place. In steel construction,tracks replace the sills and top plates used in wood-frame construction. Non-load-bearingwallsaretypicallythinner,butareotherwisesimilartoload-bearingwalls.

CommonProblemswithSteelFrameWalls

THERMAL Assteelismuchmoreconductivetoheatthanwood,thethermalefficiencyofsteel-framed BRIDGING walls ismuchlessthanthatofawood-framedwall.Steelframedwallsmayhavehalfthe

insulatingvalueofwoodwalls.Thethermalbridgescreatedbysteelstudscanbereducedthroughtheuseofinsulatedsheathingontheoutsideofthestuds,andwiththeuseofwiderstudspacing.

CORROSION Someoldersteelframewallsdidnotadequatelydealwiththermalbridgingissues,leadingtocondensationandcorrosionofthesteelstuds.Corrosionmaybeanissuewheneverthereisacondensationorwaterleakageproblem.

IMPROPER Steel studs usually come with pre-punched holes for plumbing and electrical wiring and HOLES shouldbeinstalledsothattheseholesarealignedforeasyinstallationofthemechanicaland

electricalsystems.Thereareindustry-specifiedrequirementsforotherholes.Improperholescanweakenthewall.


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REINFORCEMENT Woodnailingstripsareoftenrequiredtoallowdoorjambsandothertrimtobenailedtothe MISSING/ framing.Finishingscrewsmaybeusedinsteadofnails.Wallshavetobereinforcedinsome INADEQUATE areas,suchaswhencabinetsaretobesecuredtonon-load-bearingsteelstuds.

6.1.4Brick/StoneVeneer:Abrickorstoneveneerwallhasastructuralwood(ormetal)frameinnerwall,andafour-inchthickmasonryoutersection(veneer),whichdoesnothaveanyload-bearingresponsibility.Typically,metaltiesareusedtosecurethemasonrytothewoodframewall,andtherearenoheadercoursesinthemasonry.Theabsenceofheadersidentifiesaveneerwallinmostcases.Mostsolidmasonrywallshaveheaders.

Veneerwallshavebeenthemostcommonmasonrywalls insingle-familyhomes inmanypartsofAmericasinceabout1970.

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RAINSCREEN Sincetheearly1970s,veneerwallshavehadweepholesprovidedatthebottom.Amodern PRINCIPLE veneerwallusesarainscreenprinciple.Thisanticipatesthatwinddrivenrainwillpassthrough

amasonrywall,andasaresult,aone-inchairspaceseparatesthemasonryandthewoodstudwall.Waterrunsdowntheinnerfaceofthebrickortheoutersurfaceofthesheathinganddrainsoutthebottom.

Atthebottomrowofmasonry,everyfourthverticalmortarjoint(typically) is leftopen.Aflashingatthebottomofthewallcavitydirectswateroutthroughtheweepholes.Theflash-ingpreventsthewaterfromenteringthefoundation.Weepholesarealsousedabovedoorandwindowopenings.

Weep holes also allow pressure balancing on either side of the masonry. The air in thecavitybehindthemasonryispressurizedaswindblowsagainstthewall,reducingthepressuredifferentialacrossthemasonry.Thisreducestheamountofwaterdriventhrough.

Avariationonweepholes isropewicks ineveryfourthmortar joint inthebottomrowofmasonry.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.Iftheveneerisinadequatelytiedtothewood-framewall,themasonrymaybulgeorpullaway.Thisisanunsafecondition.

DETERIORATED Deterioratedmasonryormortarcanleadtoseriousproblems.Intheworstcases,theveneerwallhastoberebuilt.Mostbrickisnotdesignedtobeincontactwiththesoil,andshouldbekeptwellabovegrade.

WEEPHOLES If weep holes are filled or omitted, water can collect in the wall cavity, damaging thesheathingandstuds.


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FLASHING Similar results occur if theflashing is inappropriate or thespacebetweenthemasonryandsheathing is filled. The flashingcannotnormallybeseenduringaninspection.

CORBELLING Excessivecorbellingcanmakeawallunstable.(SeeSection6.1.1)

METALANGLES In some cases, the masonryveneer is supported on steelanglesboltedtothefoundation.If there isanymovement atall,themasonrymaycrack,bulge,orpullawayfromthewallbehind.

6.1.5InsulatingConcreteForms(ICFs): Insulating ConcreteForms(ICFs)areeitherpanelsorinterlocking blocks that arejoinedtogethertocreateform-work for concrete. The formsthemselves are made out ofinsulation, either rigid foam,suchaspolystyrene,oracombi-nation of concrete and foaminsulationorwoodchips.Plasticties may be used to hold theinnerandouterformstogether.Oncetheformsareinplace,con-crete is poured into the forms,filling the spaces. Rather thanremovetheforms,asinconven-tional concrete work, they areleftinplacetoactasinsulation.

ICFwallsarealsousedasfoun-dationwalls.

Afterahomeisbuilt,itmaybedifficulttoidentifythewallcon-struction.

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INSULATION ICFwallstypicallyprovideatotalR-valueof22,aboutthesameasa2x6studwall.Thesewallsalsoavoidthermalbridges (areasofhighthermalconductivity) thatarecommon inwoodstudwalls.ICFwallsarealsoairtight,whichisgoodforenergyperformance.

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

LEDGERS WherefloorsmeetICFwalls,theymayeitherrestonasillplateonthetopoftheICFwall,orbearonaledgerboardsecuredtotheICF.

OPENINGS Inmostcases,woodframingisattachedtotheICFatdoorandwindowopeningstoallowwindowframesanddoorjambstobesecured.

ELECTRICAL Electricalwiringandoutletsgenerallyrequirethe insideformtobecutaway.Theshallow WIRING depthoftheformmeansthatwiringmayrequireprotectionfrommechanicaldamage,and

receptaclesneedshallowboxes.

CommonProblemswithICFWalls

WOOD Whilepolystyreneisnotafoodsourceforpests,somewood-destroyinginsectswillnestin,or DESTROYING travelthrough,thefoam.SomeICFproductscontainchemicalprotection,andsomeICFinstal- INSECTS lationsusemechanicalbarrierstoprotectagainstinfestation.

RENOVATIONS ItismoredifficulttocreateanewopeningoralteranexistingopeninginanICFwallthanawoodframewallbecauseofthepouredconcrete.

6.1.6OtherKindsofWalls

6.1.6.1Log:Modernloghomesutilizepreciselycutlogs,keyedtogether,withgasketsbetweenlogs,whileolderlogstructuresaremuchrougher.

SIDINGS Manyolderloghomeswerecoveredwithwoodsheathingsuchasclapboardontheexteriorassoonasthehomeownerscouldaffordit.Stuccowasalsousedontheexteriorinsomecasesandplasterwasoftenappliedontheinterior.Someoldloghomeslookquitedifferentthantheydidwhentheywerebuilt.Thefoundationsweretypicallystone,andwoodshinglesorshakeswereoftentheroofingmaterial.

CHINKING Chinkingwastraditionallyusedtofillthegapsbetweenthelogs.Thiswastypicallyamortarmadeofclay,sandandbinderssuchasanimalhair.Wheregapswere large,stoneswouldoftenbefittedinbeforethechinkingwasapplied.Duetotheconsiderablemovementduetoexpansionandcontractionoflogsacrossthegrain,chinkingusuallyhadtoberedoneeveryyear,atleastinpart.


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CommonProblemswithLogWalls

WOOD Traditionallogconstructiontodayisarelativelyexpensivewaytobuild.Further,woodtends SHRINKAGE toshrinkandexpandwithchangesinmoisturecontentmuchmoreacrossthegrainthanit

doeswiththegrain.Alogwallgrowsshorterasthewooddriesandtallerwhenthewoodiswet.Awoodstudwallwillshrinkandexpandmuchlessbecausethewoodgrainisverticalratherthanhorizontal.

Ifwoodchanges itsmoisturecontent from19%to5% (typical inahouse), its lengthmaychangeby0.1%alongthegrain,butitswidthmayshrinkby2.5%acrossthegrain.Thismeansaneight-footlongstudmayonlyshrink1/10inch,whileastackoflogseightfeethighmayshrinkby2-1/2inches.Thiscanbeasignificantproblemwithwindows,doorsandotherbuild-ingcomponentsattachedtoalogwall.

CHINKING Regular maintenance is required in chinking the gaps between the logs in traditional loghomes.Themodernmaterialsnowavailableperformmuchbetter.

ROT/INSECT Rotisacommonproblemwithlogsatthebottomofthewall(wheretheymayhavebeenin DAMAGE contactwithearth)onoldhomes.Thisisnotlikelytobeaproblemwithmodernloghouses

builtonconventionalmodernfoundations.Loghomesaresusceptibletoinsectdamage,ofcourse.

CONCEALED Wherethelogshavebeencoveredwithsiding,concealedwaterdamageispossible. DAMAGE

6.1.6.2 Post and Beam: This type of construction, with wood members much larger thanconventionalwood-frameconstruction, isnotcommon,althoughitcanbefoundonoldercountrypropertiesandwascommonlyutilizedforbarns,mills,churchesandotherlargebuild-ings.Thereareprefabricatedkitsavailable.Othernamesforthistypeofconstructionincludetimber,heavytimberorsemi-millconstruction.

Thisbuildingstyleusesasmallnumberoflargewoodbeamsandposts.Thisisverydifferentfromconventionalframingthatusesalargenumberofsmallerwoodstudsandjoiststocarrytheloadsdowntothefoundations.

Traditionally,theheavypostsandbeamsweresolidwood.Inhomesbuilttoday,builtuporglue-laminatedbeamsandpostsarealsoused.Intheoriginalversions,theheavywoodpostswereoftenflaredoutatthetoptoincreasestrength.Afeatureofthesehomeswasthewaythewoodsectionswereconnected.Verysophisticatedmortiseandtenonconnectionswereutilized, as were dovetail joints. Many of the homes were assembled without nails, wooddowelsoftenbeingusedintheirplace.

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

Thesehouseswereexpensivetobuildbothintermsofmaterialsandlabor.Largepiecesofgoodqualitylumberhavebecomehardertoobtain.Becausethewoodcomponentswereveryheavy,andsophisticatedjointconnectionswereused,constructionwaslaborintensive.

CommonProblemswithPostandBeamWalls

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

function.Becauseoftheintricacyofsomeoftheconnections,therewasagooddealofroomforerror,andapoorunderstandingofloadtransmissionscouldleadtoconnectionfailures.

EXPANSION/ Thevery largetimbersundergosignificantdimensionalchangeswithchanges inmoisture CONTRACTION content.Thesebuildingsarenotstatic,expandingandcontractingwithchangesinhumid-

ity.Astimbersdriedout,checkingoftendeveloped.Checksarelongitudinalcracks,paralleltothegrainthatwidenastheygetfurtherfromtheheartwood.Inmanycases,thisisnotastructuralconcern,althoughalargecheckrunninghorizontallythroughabeamdoesreduceitsloadcarryingcapacity.Wherecontinuouscheckinginapostcouldleadtobuckling,steelclampsareprovidedaroundtheposts.

FOUNDATION Becauseoftheskeletalnatureoftheframing,largeconcentratedloadswerecarriedtotheground.Foundationsystemswereoftentooweakinareasofconcentratedloads,andmuchstrongerthantheyhadtobeinotherareas.

CONNECTIONS Thesebuildingsrelyonrelativelyfewconnections.Poorlymadeconnectionsordamagebyrotorinsectscanbemoreseriousthanonframeconstruction.

SPECIALIZED Sincethistypeofconstructionisspecialized,andnotseenfrequently,localauthoritiesand INSPECTION professional home inspectors may not be familiar with it. In some cases, a specialist is

engagedtocommentonpostandbeamstructures.

REPAIR Repairorreplacementofcomponentsofpostandbeamconstructionisoftendifficultwithoutcompromisingtheaestheticorarchitecturalappealofthehome.Thestrengthofstructuralcomponentsmustbedemonstratedusingengineeringcalculations,ratherthantables.


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6.1.6.3Panelized:Panelizeddescribesamethodofconstruction,ratherthanaspecificsystem.Intraditionalframing,theindividualcomponentsofthehouse,suchasstuds,joistsandrafters,arebroughttothesiteandthehouseisbuiltfromindividualpieces.Inpanelizedconstruction,largepanelsarebuiltoff-site,thenassembledon-siteandsecuredtothefoundation.Thesepanelsmaymakeupthefloors,walls,ceilingsandroofsofthehome.

Therearevaryingdegreesofpanelization.Panelsmaybesimplestructuralsections,ortheymay include siding, insulation, wiring and even interior finishes. Panelized constructionmay utilize wood framing, steel framing, or a combination of the two. The panels oftenincludeupgradedinsulationtreatmentandlessthermalbridgingthanfoundinconventionalconstruction.

Oncethehomeisconstructed,thereisgenerallyverylittledifferencebetweenasite-builthomeandapanelizedhome,althoughmanufacturersmaintainthatthebetterworkingenvi-ronmentandqualitycontrolpossibleinafactory,resultsinbetterbuilthomes.

6.1.6.4 Structural Insulated Panels (SIP): Structural Insulated Panels (SIPs) are one type ofpanelizedconstruction.SIPsincludethestructuralmember,insulation,airbarrierandexteriorsheathing.Thesetypesofpanelsaresometimescalledstress-skinpanelsbecausethewoodouterlayersactliketheflangesofasteelI-beam.Theinsulationactsastheweb.Weendupwithastrongstructuralmemberwithoutusingalotofmaterial.

StructuralInsulatedPanelsaretypically31/2to51/2inchesofexpandedpolystyreneinsula-tionsandwichedbetween4-footby8-footplywoodororientedstrandboard(OSB)panels.The insulation is typically 1 1/2 inchessmaller thantheskinat thetopandbottom,sothepanelscanreceivesillplatesandtopplates.SomepanelshaverecessesintheinsulationatthesidestoacceptplywoodorOSBpiecestojoinadjacentpanels.

ELECTRICAL Manypanelsincludehollowchasesintheinsulationtoaccommodateelectricalwiring.Foam WIRING hastoberemovedtomakeroomforelectricalboxes.

OTHER Similarproductsarealsomade,replacingthewoodwithsteel,aluminum,concreteandfiber- MATERIALS glass.Insulationmaterialsaremostoftenexpandedpolystyrene,butcanbepolyurethaneor

othermaterials.

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CommonProblemswithPanelizedWalls

Rot, insect attack, mechanical damage, fire damage can all be problems with woodencomponents.

WOOD Whilepolystyreneisnotafoodsourceforpests,somewood-destroyinginsectswillnestin, DESTROYING ortravelthrough,thefoam.SomeSIPproductscontainchemicalprotection,andsomeSIP INSECTS installationsusemechanicalbarrierstoprotectagainstinfestation.

6.1.6.5RammedEarth:Asthenamewouldsuggestearth,orsoil,istheprimarycomponentofarammedearthwall.Nativesoilcansometimesbeused,butascreenedengineeredsoilismostoftenused.Idealsoilsareaboutthreepartssandtoonepartclay.

Forms are constructed on conventional foundations. The forms have plumbing pipes andelectricalconduitplacedpriortopouringthesoil.Athickmixtureofearth,cementandwateris poured into the forms in layers (typically 8 inches thick). There is typically less than 5%cementand5to10%watermixedintothesoil.Eachlayeriscompacted(toaboutfiveinches),and another layer is then added and compacted. Pneumatic tampers are typically used tocompactthesoilintheforms.Theprocessisrepeateduntilthewalliscomplete.Analternativeapproachusesapumptoshootthemixtureintoone-sidedformswithairpressure.

When the forms are removed, a rough surface is presented. This can be an architecturalfeature,orthewallscanbecoveredwithplasterontheinteriorandstuccoontheexterior.Finishedwallsaretypically12to18inchesthick.

CommonProblemswithRammedEarthWalls

POOR Rammedearthhomesarelesspracticalinnorthernclimateswherethethermalmassofthe INSULATION wallsdoesnotprovidegoodinsulatingperformance.Theinsulatingvalueofan18-inchthick

wallmaybeR-4orR-5,wellbelowmodernstandardsincoldclimates.

MOISTURE Like many building systems, moisture is the enemy. While rammed earth walls are notdamagedbyoccasionalmoisture,durabilitymaybeanissueinwetclimates.Sometypesofsoilarealsomoremoisture-resistantthanothers.Exteriorsealantsareusedinsomecasestoprotecttheearthwallsfrommoisture.Largeroofoverhangsandraisedfoundationshelpkeepthewallsdry.

DAMAGE Mechanicalormoisturedamagemayresultinmissingorloosesectionsofthewallcoveringorthewallitself.Areasclosetogrademaybemorevulnerable.

WINDOWSILLS Windows may be installed close to the interior or exterior wall face. From a performancestandpoint,windowsclosetotheexteriorsurfacearepreferred,sincethiseliminatesawideexteriorwindowsillthatwilltrapwater.


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6.1.6.6 Straw Bale: Straw bale walls can be load bearing structural members, carrying thesecondfloorandroofloads,orthebalesmayfillinbetweenorwraparoundawoodpostandbeamframe.Ineithercase,thebalesprovidetheinsulationaswellasthebaseforinteriorandexteriorfinishes.

Straw is the stalk of grains such as wheat, barley, rye, oats and rice. Straw should not beconfusedwithhay,whichisgrassthatisfoodforhorses!Horseswouldnotappreciatebeingfed straw. Straw is generally considered a waste by-product of agriculture and a nuisancebecauseitisslowtodecompose.

Strawbalesusedforbuildingweigh50to90poundseach.Smallbalesmaybe14inchesby18inchesby36inches.Thelargestbalesmaybe18inchesby24inchesby48inches.Thewallsaretypically13to24inchesthickplusthethicknessofthefinishesontheinsideandoutside.

Bale walls sit on conventional foundations that, with some exceptions, should be as wideasthebales.Thereisusuallyamoisturebarrierbetweenthetopofthefoundationandthefirst row of bales. Vertical steel reinforcing bar (re-bar) projects 12 inches out the top ofthefoundationtosecurethebalestothefoundation.There-baristypically1/2inchdiameterandisplacedinthecenterofthefoundation,everytwofeetalongthewalllength,andwithin12inchesofallcorners.

Thebalesarestackedlikelargebricksintoawallconfiguration,andaresometimesconnectedto each other with steel rebar, or wood or bamboo stakes. Water pipes in the bales areinstalledincontinuoussleevestoprotectthebalesfromdamageduetoleakage.

Stuccooverwiremeshisthetypicalfinishoutside,anditcanbeusedastheinsidefinishaswell. Limeorclaybasedplastersmaybeapplieddirectly tothe interiorof thestrawbaleswithoutreinforcement.Theinnerplasterandouterstuccofinishesaddstrengthandrigidity,makingthewallastressskinpanel.

STUCCO Exteriorstuccoshouldbreathe.Stuccoswithlimetendtobemorepermeableandallowwallstodrytotheoutside.Otherstuccosarelesspermeableanddonotallowmoisturevaportopassthrough.Thisrestrictsthedryingpotentialofthewall,andmayleadtomoldorrotinthebales.ElastomericstuccoslikeExteriorInsulationandFinishingSystems(EIFS)forexample,arealsoimpermeableanddonotpromotedrying.

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CommonProblemswithStrawBaleWalls

FIRE Firevulnerabilityisroughlythesameasforwoodframewalls.Fireisactuallylessofaproblemwithstrawbalethanwoodframebecauseitishardertoignite.Strawbalewallsdonothavethenaturalchimneysthatoccurinwoodframewalls.However,oncethefireisestablished,strawbalescontributemorefuelthanwoodframeconstruction.Theslower-to-igniteissuemaybemoreimportantforoccupantsafety.

ROT Strawbalewallsarevulnerabletomoistureproblems,likemostotherexteriorwalls.Strawbalehomeswithflatroofsmaybemorepronetofailureduetowaterdamagefromtheroof.Flatroofsoftenaccumulatewater,andaleakingroofmayprovideachronicwatersourceintothewalls.

BELOWGRADE Strawbalewallsshouldbebuiltwellabovegradeleveltopreventmoisturedamage.Raisedfoundationshelpkeepthebalesdry.Largeroofoverhangsalsohelpkeepthewallsdry.

CRACKS Cracksinthestuccoandanyopeningsaroundwallpenetrationsarevulnerablepoints.Thegoalistokeepthemoistureoutofthehome.Moisturecontentisusuallylimitedto20%.Somestrawbalehouseshavemoisturemetersbuiltintomonitormoisturelevelsinthebales.

6.1.7 Party Walls: Party walls or common walls separate two homes in the same building.Theirmainfunctionistopreventthespreadoffirefromonehometothenext.

MASONRY Masonrypartywallsproviderelativelygoodfireprotectionbetweenthetwohouses,althoughtheydon’tblocksoundverywell.

WOOD-FRAME Wood-framepartitionwallsprovidelessfireprotection,althoughtheycanbebetterfromanacousticstandpoint.Somepartywallsaremasonrypartofthewayupthroughthehouse,andwood-frameintheattic.

CommonProblemswithPartyWalls

NONEINATTIC Insomeattachedhouses,thereisnowallbetweentheatticareas.Thisspacecanallowfiretospreadquicklyfromonehometoanother.Modernconstructionrulesdonotpermitthisarrangement.

6.2ArchesandHeaders(HeadersarealsocalledLintels)

Archesandheaderstransfertheloadaboveanopeninginamasonrywalltothewallsectionsoneitherside.

LOADSIN Thearchorheadersupportsatriangularsectionofmasonryabovethearch.TheheightoftheMASONRYWALLS triangle is roughly half the width of the opening. This means that a window with twenty

storiesofbrickaboverequiresonlythesamearchasawindowwithsixfeetofbrickabove.


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Thereareseveraltypesofarches.Stone,brickandconcretearethemostcommonmaterialsused.Segmentalarchesarethemostcommon,madeupofseveralpieces.Thearchtypicallyhasariseofatleastoneinchforeachfootofitsspan.

Jack arches have flat tops and bottoms and are often decorative but not functional. Steelheaderstypicallysupportthearch.Thisisnotacommontypeofarch.

Somearcheshavealargermasonryunitatthetop/center.Thisiscalledakeystone,andisoftenthearchitecturalfocusofanarchandwindowsystem.

Headersaretypicallyflat,andusetheinherentstrengthofthematerialtotransmittheload,ratherthanthearchprinciple.Headers(calledlintelsinsomeareas)maybesteel,wood,stoneorconcrete.

Headersaremadeofasinglepiece,wherearchesarebuiltfromseveralpieces.

CommonProblemswithArchesandHeaders

TOOFLATOR Failureinarchesiscommonwheretheriseisverymodest,orthearchisnotquitewideenough TOONARROW toclearlyspantheopening.Anothercommon problemwitharches is slight movement of

thewallsoneitherside.Thisisparticularlycommonwhereawindowordooropeningisclosetotheendofawall.Ononesideofthearch,theremaynotbeenoughmasstoresistthelateralthrustofthearchtransferringitsloadtothewallbeside.Asthethinsectionofwallpushesoutward,thearchdrops.

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DETERIORATION/ Mortarormasonrydeteriorationcan,ofcourse,leadtofailure.Buildingsettlementmayallow LEANING thearchtoopenupanddrop.Anotherproblemisforwardmovementofthearchoutaway

fromthebuilding.Thisisusuallycausedbyfoundationmovementormortarandmasonrydeterioration.Correctiveactionsincluderebuildingthearchoraddingaheader.

UNDERSIZED/ Headersmaybeundersizedfortheload.Inadequateendbearingoftheheadersmayleadto POOREND failure.Steelheaders(lintels)onmasonrywallsshouldextendatleastsixinchesbeyondthe BEARING openingoneitherside.Thiscannotusuallybeseen.

RUST/ROT/ Steel lintelsaresubjecttorust. SPALLING/ The rusting steel expands and CRACKING may cause horizontal cracks in

themortarjointsatthecornersof the opening. Wood headersare susceptible to rot and in-sectattack.Concreteandstoneheadersaresubjecttocrackingorspalling.

MISSING Inamateurishconstructionproj-ects,windowsmaybeaddedtomasonry walls or brick veneerwalls with no arch or headerprovided. This will often workin the short term, but prob-lemsusuallydevelopovertime.Missing or inadequate headersshouldbereplaced.

CAULKING Steelheaders(lintels)supportingbrickveneershouldhavenocaulkingbetweenthesteelandthebrickabove.Caulkingmaytrapwaterandrustthesteel.


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7.0 RoofFraming

Theroofframingisanassemblyofwoodorsteelcomponents.Theroofframingtiesthebuild-ingtogether,addingrigidityandprovidingasurfacefortheroofcovering.Theroofframingalsosupportstheceilingfinishesbelow.Wewill lookattheindividualcomponentsofroofframingsystems.

7.1Rafters–Wood

Rafterscarry the loads from the roof sheathing, roofcovering,wind,water, snowand ice.Theseloadsaretransmittedthroughtherafterstobearingwallsorbeamsbelow.Thetermrafterisassociatedwithslopedroofs.Whenthesemembersarefoundonaflatroof,theyarehorizontalandcalledroofjoists,althoughtheydothesamejob.

Rafters can usually be seen overhead when standing in the attic. Some rafters supportfinishedceilings,creatingacathedralceiling.Inthiscase,insulationisoftenfitbetweentherafters.

Woodraftersaretypically2x4s,2x6sor2x8s,spaced16to24inchesoncenter.Conventionalraftershavebeenreplacedbytrussesinmostmodernhomeconstruction.Theengineeredtrussescanspangreaterdistanceslessexpensivelythanconventionalrafters.

When calculating the span of a rafter system, the horizontal span rather than the actuallengthoftherafterisused.Kneewallsorpurlinsmayprovideintermediatesupport,reducingthespan.Collartieshelpkeepraftersinplace.Ceilingjoistsarehorizontalmembersthatoftentiethebottomsofopposingrafterstogether,makingastrongtriangle.

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CommonProblemswithWoodRafters

OVERSPANNED/ If rafters are overspanned or spaced too far apart, the roof will sag. If rafters are not RAFTERSPREAD adequatelysecuredto thewallsat thebottomedge, the raftersmayspreadapart.This is

commononolderhouses,particularlywithgableroofs.Itisoftennotedattheeaves,becausethesoffitspullawayfromthehousewallastheraftersspread.Inothercases,thespreadingrafterspushthetopofthewalloutward.Thiscanbeveryserious.

Raftersmayalsoseparateattheroofridgeifconnectionsandsupportarepoor.

ROT/INSECT Wood rafters are susceptible to rot, insect, fire and mechanical damage. Rafters may DAMAGE/SPLIT splitunderload.

CONDENSATION Attics in cold climates with good insulation but poor ventilation may be susceptible to LEADSTOROT condensation problems. Condensation will attack the roof sheathing and the rafters. Left

unchecked,thiscanleadtoroofstructurefailure.Correctiveactionincludesimprovedventila-tionandreplacingdamagedwood.Moldoftendevelopsinatticsasaresultofcondensation.

SAG– Concentrated loads may be a problem around roof dormers. The load from a dormer is CONCENTRATED transferredtotheraftersoneithersideofthedormer.Unlesstheseraftersarestrengthened, LOADS theroofmaysagarounddormers.

In cold climates, roofs mayfail because of a concentratedsnow load. Split-level housesaresusceptibletothisproblem,forexample.Itisnotunusualforsnowdriftstoformonthelowerroof,nearthewallofthehighersection. This leads to big loadsontheraftersortrussesintheseareas.Theraftersmaycrack,sagorspreadatthebottom.Trussesmaycollapse.

7.2RoofTrusses–Wood

Rooftrussesareengineeredassembliesthatperformthesamefunctionasrafters,collarties,kneewalls,purlinsandceilingjoists.Therooftrusscarriestheroofsheathingandshingles,andtheliveloads,transferringtheroofloadstotheoutsideorbearingwalls.Thebottomofthetrussalsosupportstheceilingfinish.

ThereareotherengineeredwoodframingsystemsincludingwoodI-joists,andotherconfigu-rations.Adesignreviewoftheseisbeyondthescopeofahomeinspection.Theperformanceevaluationissimilartotrussesandrafters.


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Most trusses in homes are made of wood. The top and bottom members of the truss arecalledchords.Theinteriormembersofatrussarecalledwebs.Trussmembersarefastenedtogetherwithgussetplates.Thesemaybemadeofplywoodorsteel.Differentconfigurationsoftrusseshavedifferentstrengths,andengineerscanusetheshapeandcomponentsizethatbestsuitsthem.Trussesareengineeredsystems.Trussesarenormallyspaced24inchesapart,butthiscanvary,againdependingonthespansanddepthoftrussdesired.

Therearetwocommontrusstypesusedresidentially.TheFinkor“W”haswebmembersthatforma“W”.TheHowetrusscanbeidentifiedbyverticalwebmembers,includingaverticalwebrunninguptothepeak.Therearemanyvariationsofthesefoundinresidentialconstruc-tion.

Ineithertrusstype,thewebsshouldbeatleast2x4s,unlessspecialengineeringconsiderationhasbeengiven.Wherethecompressionwebsarelongerthansixfeet,theyaresusceptibletobucklingunderheavyloads.Braces,suchas1x4s,shouldbefastenedtothemidpointsofthesewebs.

Where the bottom chord hasa long span between supportpoints, it may not be strongenoughtocarrytheceilingload.If the span is more than tenfeet between support points,thebottomchordshouldbeatleast a 2x5. If the span is morethan 12 feet, the bottom chordshould be a 2x6. Again, specialengineering consideration canresult in deviations from theseguidelines.

CommonProblemswithWoodRoofTrusses

Likeanywoodmember,trussesaresubjecttorot, insectdamage,mechanicaldamageandfire.

CUT Individualchordsorwebsthatarecutordamagedcanbeaseriousproblem.Cuttingatrussinonespotmayseriouslycompromisetheentiretruss.Wheretrussesarecuttoaccommodatechimneysorotherinterruptionsintheroofline,engineeringconsiderationshouldbegiven.

FASTENING Trussesmustbewellsecuredtoperformwell.

OVERSPANNING Overspanningoftrussescanleadtodeflectionand,inworstcases,roofcollapse.Heavierroofmaterialsuchasconcretetile,orgreatersnowloadsthanexpected,duetounusualconditionsordriftingmaycausetheproblems.Overspanningcannotbeidentifiedduringahomeinspec-tion,butevidenceofdeflectionorfailureisnoted.

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REPAIRS– Reinforcing overspanned or damaged trusses is more difficult than strengthening a rafter DESIGNNEEDED roofsystem.Anengineershoulddesigntherepair.

LONGWEBS– Trusses with web members longer than six feet may be subject to buckling. BracesBRACINGNEEDED shouldbeaddedtothemidpointsofthewebs.Onebraceattachedtoeachwebwithtwonails

shouldconnectseveralwebsinadjacenttrusses.Thebracesshouldbeatleast1x4s.

INADEQUATE Undersizedbottomchordsshouldbestiffenedtopreventceilingsagandcrackingofceiling CEILING finishes.Addingasecondmembertothebottomchordwouldnormallybesatisfactory. SUPPORT

TRUSSUPLIFT Aphenomenonknownastrussupliftisrelativelycommonincoldclimates.Thetemperatureandhumiditychangesintheatticduringthewintermonthsaffectthesectionsofthetrussabovetheinsulationleveldifferentlythanthebottomchord,whichisburiedintheinsulation.Thisresultsinanupwardbowingofthebottomchord.

Theresultoftrussupliftisthatthecentersectionofthebottomchordmovesup,andgapsaslargeas1-1/2inchesappearatthetopoftheinteriorwalls,wheretheyjointheceiling.Theceilingispickedupbythetruss.Itisalsopossiblethattheinteriorwallbelowwillbeliftedup,andseparationwilloccurbetweenthewallandthefloor.

Acommonsolutionistosecureamoldingtotheceiling(butnottothewall).Astheceilingmovesupanddown,themoldingwillslideupanddownthewall,concealingthegap.

Anothersolutionistodisconnecttheceilingfinishesfromthetrussduringconstructionandtocliptheceilingfinishestothewall.Thisallowstheceilingtobendveryslightly,butnottocrack.

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7.3SteelFraming

Steelroofframingperformsverymuchlikewoodframing.Likewood,steelroofframingmaybemanufacturedtrussesorsite-assembledraftersandjoists.Theprinciplesofwoodframingalsoapplytosteelroofframing,althoughcontinuousbridgingontheraftersisoftenneeded,either on the underside, or through the knockouts. The undersides of joists will twist andmoveunlesstheyarerestrained.

Woodsheathingmaterials,suchasplywood,arescrewedtothesteel roof structure. Roofingmaterialsareinstalledoverthissheathingasnormal.

CommonProblemswithSteelRoofFraming

RUST Steelis,ofcourse,vulnerabletocorrosionwithlong-termexposuretomoisture.

HOLES Anyholesthatarecreatedshouldbeatleast10inchesawayfromtheendoftherafter,posi-tionedinthemiddleoftherafter,andshouldnotbewiderthan1-1/2inchesandnotlongerthanfourinches,unlesstheyarereinforced.

NODESIGN Steelroofsareengineeredsystems,andaswithwoodtrusses,homeinspectorsdonotassess REVIEW theirdesign.

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7.4CollarTies

Collartiesmaybeinstalledtopreventraftermovement.Thesearetypicallywoodmembers(atleast1x4s)installedhorizontallyacrosstheatticspace.Theyareconnectedateitherendtoopposingrafters.Insomecircumstances,metalstrapsmaybeusedinsteadofcollartiestopreventuplift.

CommonProblemswithCollarTies

MISSING,WRONG Missingcollartiescanbeaddedreadily.Collartiesmaybeinstalledincorrectlyorfastened LOCATIONOR poorly. POOR CONNECTION

BUCKLEDAND When collar ties are installed to prevent rafter sagging, the compression from opposing BROKEN raftersmaybuckleandcrackthecollarties.Addingbraceswillpreventthis.Brokencollarties

canbereplacedasneeded.

7.5Purlins

Purlinspreventraftersag.Thesearewoodcomponentsthesamesizeastherafterstheysup-port.Theyarenailedtotheundersideoftheraftersandaresupported,inturn,by2x4braces,whichextenddown,usuallyonanangleratherthanvertically,toabearingwallbelow.Seeillustrationonnextpage.

CommonProblemswithPurlins

Likeanywoodcomponent,purlinsaresubjecttorot,insectandmechanicaldamage.

STRUTS–MISSING Bracesorstrutsnomorethanfourfeetapartshouldsupportthepurlins.

STRUTS–SLOPE Strutsshouldbeinstalledwithaslopeofnotlessthan45degreesfromhorizontal.Anylessthanthisandthestrutswillnotproperlytransfertheirload.

STRUTS– Thestrutsthemselvesshouldbebracediftheyarelongerthaneightfeet.Astripoflumber UNBRACED attachedperpendiculartothestrutswillpreventbuckling.


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7.6KneeWalls

Knee walls are intermediatesupports that prevent raftersag. These small walls in theatticaretypicallybuiltwith2x4woodstuds.Theyrunfromtheatticflooruptotheundersideoftheraftersneartheirmid-point.In 1-1/2 or 2-1/2 story houses,knee walls form the walls of aroomontheupperfloor.Theserooms often have a partlyslopedceilingasaresult.

CommonProblemswithKneeWalls

POORLYSECURED/ Ifthekneewallsarenotadequatelysecuredtotheraftersaboveorthejoistsbelow,theywill WEAKFLOOR move.Ifthefloorjoistsystembelowisnotstrongenough,orthereisnopartitionbelow,this

canleadtodeflectionanddamageintheceilingbelow.

LOCATION Ifthekneewallisnotnearthemidspanoftherafters,itmaynotbeeffectiveinpreventingraftersag.

DAMAGE/ROT/ Likeanywoodcomponent,kneewallsaresubjecttorot,insectandmechanicaldamage. INSECTDAMAGE

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7.7RoofSheathing

Sheathingsupportstheroofcovering,transmittingtheloadsfromthecoveringandtheliveloadsduetowater,snowandwindtotherafters,trussesorroofjoists.

Upuntilthe1950s,virtuallyallroofsheathingwaswoodplank.Plywoodroofsheathingin4-footby8-footpanelsbecamepopularinthe1960s,andwaferboardpanelsarrivedinthe1970s.

Plywoodshouldbelaidwiththesurfacegrainperpendiculartotherafters,trussesorjoists.Theeight-footlengthshouldbeacrosstherafterswitheachendsupportedbyarafter.Theotheredgesshouldalsobesupported,typicallybymetal“H”clipslocatedbetweenrafters.Theseclipsnotonlysupporttheedges,butkeepthesheetsslightlyseparatedtoallowforexpansionwithoutbuckling.

Thethicknessofthesheathingisdeterminedbythespacingoftheraftersandtheliveroofloads. Modern construction typically employs trusses or rafters on 24 inch centers andplywoodsheathing3/8inchthick(orwaferboardsheathing7/16inchthick).Thisleadstoafairlyspringyroofsurfacewhenwalkedupon.Unusuallyheavyloadsorslightweakeningoftheplywoodduetohighmoisture levels intheatticcan leadtosaggingof thesheathingbetweenthesupports.Normallythisisnotastructuralflaw,althoughitisunsightly.


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CommonProblemswithRoofSheathing

DAMAGE/ROT/ Likeanywoodcomponent,roofsheathingissubjecttorot, insectdamageandmechanical INSECTDAMAGE damage.

DAMAGE– Condensationinanatticcancauseproblems.Plywoodroofsheathingwillbegintodelaminate CONDENSATION andwaferboardsheathingwillswell.Thiscancauselossofsheathingstrengthandrender

thenailingineffectiveasnailsarepulledoutoftheraftersorthroughthesheathing.Inseverecases,theroofcoveringhastoberemovedandthesheathingreplaced.

Concealedcondensationincathedralroofsisacommonproblemandconsiderabledamagecanoccurbeforethereareanyvisualclues.

MOLD Mold often appears when there has been condensation in the attic. Once the moisture isremoved,themoldstopsgrowing.Removaloftheinactivemoldisnotnecessary,althoughmanyhomeownersremoveitbecauseofthestigmaattachedtomold.

TOOTHIN Sheathingthatistoothinfortheapplicationwillsagunderload.Aesthetically,thisisoftenunacceptable,althoughsaggingtothepointoffailureisunusual.

Sheathingthicknessisdeterminedinpartbythespacingoftheraftersortrussesbelow.Thick-ersheathingisneededwhenthespansaregreater.Sheathingthicknessisalsodeterminedbytheliveloadsfromwindandsnowaswellasdeadloadsfromroofcoverings.

EDGESUPPORT Unsupported edges of roof sheathing may lead to differential movement between twopanels.Thiscanleadtohorizontalridgesappearingintheroofing.Ifthesheathingisunusu-allythick,edgesupportisnotnecessary.

FIRERETARDANT Fire retardant treated (FRT) plywood was recognized as a problem in the late 1980s. TREATED(FRT) Delaminationandweakeningofthisplywoodcanleadtoalossofroofshinglesandultimately PLYWOOD collapse.Whereithasbeguntofail,itshouldbereplaced.

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8.0MasonryChimneys

Thestructuralfunctionofachimneyistocarryitsownweightdowntothefoundationsandfootingswithoutmoving.(WelookatotherchimneyfunctionsintheRoofingandHeatingchapters.)

CommonProblemswithMasonryChimneys

LEANING Chimneysthatleanabovetherooflevelshouldbebracedorrepairedasnecessary,withoutdelay.

FOUNDATION Localized foundation settle- PROBLEMS ment in a house around the

chimney is fairly common,typically because the founda-tionswerenotlargeenoughtocarrytheweightofthemason-ry.Thechimneymayeventuallyfall over, but the problem canbecomeveryseriousbeforethispoint.Achimneythatbeginstolean or pull away may developcracks or gaps, which allowsmoke and heat to get nearcombustiblematerials,creatingafirehazard.

CRACKING/ Cracking, spalling and deterio- DETERIORATED rated mortar are common MASONRYOR problems with any exterior MORTAR masonry.

CORBELLING Chimneys with excessive corbelling (one row of bricks projecting out and overhangingtherowbelow)orundersizedfoundationsarepronetomovement.(SeeSection6.1.1)


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THREESIDED Occasionally,chimneysareaddedtotheoutsideofexistinghouses.Manyoftheseareonlythreesided,usingthehousewallasthefourthside.Thisisusuallyconsideredunsafealthoughit may be acceptable where abrickveneerwallismadeofsol-idmasonryunitsand isspacedoutat least1/2 inchfromcom-bustiblesheathing.Onmasonrywalls,12inchesofsolidmasonrymustseparatethefluefromanywood joists or beams. A visualinspection cannot determinewhethertheinstallationissafe.

WOOD Woodbuildingmembersshouldnot contact masonry chimneystoavoidoverheating.

CONTACTING Generally speaking, interior CHIMNEYS wood should be at least two

inchesfromthechimney.Onex-teriorwood,thiscanbereducedto1/2inch.Whereitisnecessarytoframeintothechimney,thereshouldbe12inchesofsolidmasonrybetweenthewoodandtheflue.

FIREBLOCKING Thespacebetweenmasonrychimneysandwoodframingcanprovideachannelforfireto MISSING movequicklyupthroughhouse.Fireblockingatceilinglevelshelpspreventthis.Theblock-

ingmaterialcanbecompressedfiberglassinsulationorothernon-combustiblematerial.Itisoftendifficulttoseeduringahomeinspectionwhetherthishasbeeninstalled.

9.0ThingsThatCauseStructuralProblems

Let’slookatsomeofthecommonthingsthatgowrongwiththestructure.Whiletherearesomeproblemsthatarespecifictoonecomponent(trussupliftproblems,forexample,areuniquetowoodrooftrusses),therearetwobroadsourcesofproblems–poorconstructionandthingsthatattackthebuilding.

9.1PoorConstruction

Housecomponentsmayfailbecausetheywerebuiltwithimpropermaterials,orthemateri-alswerepoorlyassembled.Examples includeundersizedstructuralmembers likefootings,beams and joists. Poor connection issues include inadequate nailing, missing or poorlyinstalled joist hangers, bad post-to-beam joints, or using the wrong fasteners, like nailsinsteadofboltstosecureadecktoabuilding.

Therearehundredsofexamplesofpoorconstructionpracticescommontohomes.

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9.2ThingsthatAttackHouses

Let’sassumethehomewasproperlybuilt.Wearenotoutofthewoodsyet!Lotscanstillgowrong,andoftendoes.Someofthethingsthathappenareuniversal,andsomearespecific.Rotandinsectsattackwoodmembersbutnotconcrete,forinstance.We’llstartwithsomethingsthatapplytoallormosthomes,andthenmovetosomethatareregional.

9.2.1 Rot Affects Wood: All wood and wood-based building materials are subject to rot.Componentsthataremorelikelytogetwetfrequentlyaremorelikelytorot.

FUNGUS Rotoccursinwoodundercertainconditionsoftemperature,moistureandinthepresenceofoxygen(It’salwayspresent!).Thedecayiscausedbyfungus,whichattacksthewoodcells,causingthecells(andthewoodasawhole)tocollapse.Thefungusthatcausesrotrequiresatemperaturebetwen40°F.and115°F.tobeactive.Abovethattemperature,thefunguscanbekilledand,belowthattemperature,thefungusbecomesdormant,butcanbereactivatedoncethetemperatureincreases.

MOISTURE Sufficient moisture is needed for rot to occur. When the moisture content of the wood NEEDED exceedsapproximately20%,fungussporesthatarenaturallypresentintheatmospherecan

besustainedandgrowwithinthewood.Oncethefungusisestablished,itwillcontinuetogrowanddecaythewoodaslongasthewoodremainswet.Ifthelumberisdriedtobelow20%moisturecontent,therotwillspreadnofurtherandwillbecomedormant.

Astherotprogresses,thewoodcellwallscollapse,leadingtoalossofstrengthandtheforma-tionofcracksperpendiculartoandparalleltothegrain.Thewoodcanoftenbebrokenoffinsmallcubes.

OXYGEN Oxygenmustbepresentforrottodevelop.Thisexplainswhywoodsubmergedinwaterwill NEEDED notrot.Undernormalcircumstancesinhouses,thereisalwaysoxygentosupportrotfungi

growth.

RecommendedPracticesandSolutionsforRot

AVOIDTRAPPED Wood structures must be properly designed to resist rot. Wherever possible, the design WATER shouldpreventcyclicalwettingandentrapmentofmoisture.Alljointsshouldbefreedraining

todryquickly.Ledges,valleysandtroughswherewatercancollectshouldbeavoided.Endgrainsofwoodshouldbewellprotected,astheyarecapableofsoakinguplargeamountsofwaterthroughcapillaryaction.

ROTRESISTANT Somewoods,includingcedarandcypress,forexample,arenaturallyresistanttodecayfungi. WOOD Variouswoodtreatments(suchaspressuretreating),canenhancetherotresistanceofwood.

Inthecaseofpressuretreating,copperarsenatesalts(typically)areforcedintothewoodcellsunderpressure.Itisthesesaltsthatgivethewoodagreenishtint.Thereareothertreatmentsdesigned to provide resistance to rot, mold and insect attack. They can produce wood ofdifferentcolors,includingblue.

AVOIDWOOD/ Avoidingthedirectcontactofwoodwithsoilwillinhibitrotbyhelpingtokeepitdry.Good SOILCONTACT ventilationofporchesandcrawlspaces,forexample,isalsoimportantineliminatingrot.


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PREVENTLEAKS Appropriate flashing details at joints that promote good drainage, and a well-maintainedprotectivecoatofpaintorstain,willalsohelptofightrot.Leakingroofsandgutters,ifuncor-rected,cancreateanidealenvironmentfortheestablishmentofrotfungi.Similarly,woodintheareaofkitchensandbathroomscanbesusceptibletorotifthereareleakingpipesorfixtures.

9.2.2InsectsAttackWood:Insectscandoseriousdamagetowoodstructures.Termitesdothemostdamagebecausetheyeatthewood,buttherearemanyinsectsthatdamagewoodbynestinginit.Theseincludecarpenterantsandpowderpostbeetles.

Homeinspectorsdonotperformpestinspectionsaspartofahomeinspection.Buttheydolookforevidenceofthestructuraldamagethatresults.Theevidenceisoftenhiddenorverysubtle.

9.2.3FireAttacksWoodandSteel:Firedamagetoabuildingcanbesevereorcosmetic.Asaverygeneralrule,majorstructuralmemberswithlessthan1/4inchofchardonotrequirere-supporting.This,ofcourse,dependsonthesize,orientationandfunctionofthemember.Wherethereisdoubt,specialistscanbeconsulted.

Anothertypeoffiredamageshouldbeconsidered.Wherewoodstructuralcomponentsaretooclosetofireplaces,furnaces,etc.,thewoodaroundthemmaybegintocharasitoverheats.Thiscanoccurattemperaturesaslowas250°F.Thiswillallowthewoodtoigniteeasilyifex-posedtohighertemperaturesevenbriefly.Charredwoodaroundheatgeneratingappliancesisadangersignthatshouldnotbeignored.

Althoughsteeldoesnotburninthesensethatwooddoes,itlosesitsstrengthquicklywhenexposedtofire.Steelmemberstypicallyfailbeforewoodcomponentsinafire.

9.2.4RustAttacksMetal:Rustorcorrosionaffectsmostmetalstosomeextent.Rustingsteelisacommonhouseproblemwithrespecttopostsandbeamsaswellasfastenerslikenails,screwsandbolts.Unprotectedsteelrustswhenexposedtowater.Steelthatisexpectedtobewetcanbepaintedortreatedwithrustinhibitorssuchasgalvanizing(addingzinctothesteeltoresistrust).Hotdipgalvanizingismoreeffectivethanelectroplategalvanizing,althoughneitherguaranteethattherewillbenorust.Stainlesssteelismorecorrosionresistantthangalvanizedsteelbutisnotcommonasabuildingmaterial.Therearedifferenttypesofstain-lesssteel.

EXPANDINGRUST Rust can cause metal components to weaken but can also damage other materials. Steelexpands as it rusts, exerting tremendous force. If the steel is embedded in concrete, thedamagecanbesignificant.Steelreinforcingbarscanbreak(spall)concreteandsteelrailingscandamageconcreteporches,decksandbalconies,forexample.

9.2.5MechanicalDamageAffectsAllBuildingMaterials:Woodandsteelaremoresuscep-tiblethanconcrete,butdamageispossibleinanyofthese.

Mechanical damage to wood members can take several forms. It may be split, broken orcrushedduringhandlingorwhilethebuildingisunderconstruction.Itiscommonforsomewoodinahomebeingbuilttosufferminormechanicaldamage.Theextentandlocationofthedamagedeterminewhetherreplacementorrepairisneeded.Theentiresystemmustalsobeconsidered.Ifthewall,roof,orfloorsystemissignificantlyover-designed,onedamagedmembermaynotbecritical.

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NOTCHESAND Similarconsiderationisgiventomechanicaldamagecausedbycutting,notchingordrilling HOLES holesinwoodmembers.Again,thereareseveralcriteriathathelpdeterminewhethercorrec-

tiveactioniswarranted.

IMPACTDAMAGE Impactdamagemaybefromvehicles,animalsorpeople.Thedamagecanbetrivialordevas-tating.

9.2.6GroundMovement–EarthquakeandSoilConditions:Nomatterhowwellthehomeisbuilt,whenthegroundbelowmoves,damageislikely.EarthquakesaresignificantproblemsinsomepartsofNorthAmerica.Erosion,landslidesandundergroundstreamsunderminingbuildingsareexamplesoflessdramaticgroundmovement.Homesbuiltonweaksoilsmayfailcatastrophically.Expansivesoilscanalsocausedramaticbuildingdamage.Anotherkindofsoilmovementspecifictocoldclimatesisfrostheave,wherethesoilbeloworbesidethebuildingdamagesconcretefloorsandwalls.

Constructiontechniquescanimprovethechancesofsuccessfullywithstandingdamage,buttherearenoguaranteeswithnature.Duringanearthquake,thehouseshouldactasaunit,with the foundations, floors, walls, and roof moving together. Problems arise when thesemoveindependentlyofeachother.

RISKFACTOR Unreinforcedmasonrybuildingsandstructuresaremorevulnerabletoearthquakedamagethanwoodframehomes.Woodframehomeswithshearwallsarebetterthanordinarywoodframebuildings.Homeswiththestructuralcomponentstiedtogetherandtiedtothefounda-tionarebetterthanconventionallyframedhouses.Singlestoryhomesarebetterthantwostoryhomes.

COMMON Failuremodesduringearthquakestypicallyincludethingslikepostsmovingoffpiers,beams PROBLEMS movingoffposts,cripplewallsfallingofffoundations,andmasonrychimneyscollapsing.

TWO The two critical strategies in reducing earthquake damage are tying the house structural STRATEGIES componentstogetherandusingshearwallstominimizerackingofthestructure.

TYINGHOMES Special fasteners are used, both during new construction and in upgrading existing TOGETHER homes. The hardware includes sill anchors (mechanical wedge-type in retrofit situations),

hangers,holddowns(tiedowns),postcaps,strapsandhurricaneclips(hurricaneties).Woodmemberscanalsobeusedtotiecomponentstogether.

SECUREMENT The fasteners may be nailed, bolted or embedded in concrete. Engineers, manufacturersanddesignershavedifferingopinionsaboutthetype,size,locationandnumberoffastenersrequiredinanysituation.Thegoalistotiethebuildingtogethertopreventlateralmovementoroverturning.Thesillsshouldbetiedtofoundationsorfloorslabs,postsshouldbetiedtopiers,beamsshouldbetiedtoposts,floorsshouldbetiedtosills,wallsshouldbetiedtofloorsandsills,androofsshouldbetiedtowalls.

BRACINGPOSTS Adjacentpostsinsub-gradeareasmaybesupportedwith2x4diagonalbracestohelpresistlateralforces.


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SHEARWALLS Shearwalls help wood frame walls resist racking caused by the strong lateral forces thatoccurduringearthquakes.Shearwallsaretypically3⁄8to1⁄2inchplywoodorwaferboard.Theymustextendthefullheightofthewalltobeeffective.Shearwallsaretypicallytheexteriorwallsofawoodframehome.Someinteriorwallsonlargehomesmayalsobeshearwalls.

DETAILS Theplywoodorwaferboardpanelsmaybeinstalledontheinnerorouterfacesofstudwalls.Theyarenotneededonboth.Thepanelsareinstalledvertically,exceptoncripplewallslessthanfourfeettall.Gapsofroughly1/8inchareleftaroundalledgesofpanelstoallowforexpansionduetochangesinmoisturecontent.Withoutthesegaps,thepanelsmaybucklewhentheyswell.

SECUREMENT Paneledgesarenailedeveryfourtosixinches,dependingonthedesignerandthesituation,and every 12 inches in the field of the panels. All four edges of panels must be backed bysomethingsolidsuchassills,studs,rimjoists,topplatesorblocking.

HOLDDOWNS Holddownsareprovidedateachcornerofthehomeandateachendofeveryshearwall.HolddownsareheavyL-shapedbracketsthatsecuretheshearwalltothefoundation.Holddownsareusuallysecuredwithbolts.

CRIPPLEWALLS Cripplewallsareshortwoodframewallsthatspanfromthefoundationtothefirstfloor.Theyare vulnerable to earthquakes because they have little resistance to lateral forces. Cripplewallscanbeconvertedtoshearwallsfromtheinsidebyaddingplywoodorwaferboardpanelstothestuds.Studspacesaretypicallyventedintothesub-gradeareawith1⁄2inchdiameterholesatthetopandbottomofeachstudcavity.

STRAP Heavyappliancessuchaswaterheaters,furnaces,refrigerators,washingmachinesandstoves APPLIANCES shouldbestrappedtothebuildingtokeeptheminplace. DOWN

SPECIALGAS Gasvalvesthatshutoffautomaticallyifthegaslinerupturescanbeprovidednearthegas VALVES meterinearthquakeproneareas.

CHIMNEYS Unreinforced masonry chimneys are common on old homes and there is no easy way to VALVE improvetheirresistancetoearthquake.Somepeopleput3/4-inchplywoodonatticfloorsto

preventbricksfallingoffchimneysfromcomingthroughceilingsintothehome.

9.2.7HurricaneandTornadoes:Earthquakes impose lateral forcesonhomes, for themostpart.Hurricanesexertlateralforcesandupliftforces.Whilesimilartoearthquakesinsomerespects,hurricanes,tornadoesandotherhighwindspresentseparateproblems.

RISKFACTOR Hurricanesareregionalissues,andthereareotherwind-relatedproblemssuchastwistersandtornadoesthatarealsosomewhatregional.ThesoutheasternUnitedStatesisthemostprominenthurricaneareainNorthAmerica.Severaldevastatinghurricaneshaveoccurredinthisareaandbuildingofficials, insurancecompanies,buildersandhomeownersall lookathomesdifferentlyasaresult.

Considerableinvestigationandresearchhasbeendoneafterhurricanes,andmuchhasbeenlearnedaboutthemechanismsoffailure.Hurricanesusuallycarryheavyrainsandmuchofthedamagefromhurricanesiscausedbywater.Windisnottheonlyissue,butoftencreatestheopeningsthatallowwaterintohomes.Windcarriedprojectilesareanotherproblem.

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KEYISSUES Manybelievethethreekeyissuesinhurricaneresistanceforhomesare:theroofsheathingmustbewellsecuredtotheroofframing,theroofframingmustbewellsecuredtothewalls,andopeningsincludingdoorsandwindowsmustbeprotectedfromflyingdebris.

DECKNAILING Roofsheathingshouldbenailedatsix-inchcentersalongpaneledgesandat12-inchcentersinthefield.Sheathingatoverhangsisoftennailedatfour-inchcentersbecausewindforcescanbegreaterhere.

HURRICANECLIPS Hurricaneclipsorstrapsareusedtosecureroofframingtowalls.Strapsarealsousedtofastenwalltopplatestothewallsthemselves.

OPENINGS Openingscanbeprotectedthroughspecialimpactresistantdoorsandwindows,orshutters,plywoodcoversorsomeothershieldingprotectionontheoutside.

ROOFBRACING Trussroofscanbestrengthenedwithwoodbracesonthewebsandthechords.Gableendwallshaveprovenvulnerabletohurricanewinds,andareoftenstrengthenedwithbracesintheattic.

WINDRESISTANT Asphaltshinglesareoftenblownoffroofsduringhurricanesandotherhighwinds.Manu- SHINGLES facturershavebeenmakingeffortstoincreasethewindresistanceofroofingmaterials.Some

areascallformopped-inasphaltunderlaymentbeneathshingleswheretheriskofshinglelossissignificant.

CONCRETETILES Concretetileshavealsoblownoffroofsinhurricanes.Theseareworsethanasphaltshinglesbecause the heavy tiles become dangerous projectiles. Improved installation techniquesincludefullmortarbedsforconcretetiles.

HIPROOFS Designersarebeingencouragedtomovefromgableroofstohiproofs,sincehipsare lesslikelytofail.Hiproofshavenoverticalgablewallto‘catchthewind’.

GARAGEDOORS Garagedoorshavebeenaproblembecausetheyblowineasily.Strongerdoors,hardwareandtracksareapartialsolution.

NOGUARANTEES Aswithearthquakes,homescanbebuilttoimprovetheirchanceofsurvivingseriouswinds,butnatureissostrongthattherearenoguarantees.

9.2.8Flood:Flooddamagecanbesevereandmaybethemostseriousimpactofhurricanesandearthquakes.

Homesinfloodproneareasmaybebuiltonstiltstoreducetheriskofdamageorlossofbuild-ing,buttherearefewabsoluteswithflooding,aswithothernaturalforces.


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