study guide foundation walls - education.nachi.org

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StudyGuideforInspectingFoundationWallsandPiersCourseThisstudyguidecanhelpyou:

• takenotes;• readandstudyoffline;• organizeinformation;and• prepareforassignmentsandassessments.

AsamemberofInterNACHI,youmaycheckyoureducationfolder,transcript,andcoursecompletionsbyloggingintoyourMembers-OnlyAccountatwww.nachi.org/account.Topurchasetextbooks(printedandelectronic),visitInterNACHI’secommercepartnerInspectorOutletatwww.inspectoroutlet.com.Copyright©2007-2015InternationalAssociationofCertifiedHomeInspectors,Inc.

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StudentIdentificationandVerificationStudentVerificationByenrollinginthiscourse,thestudentherebyatteststhats/heisthepersoncompletingallcoursework.S/heunderstandsthathavinganotherpersoncompletethecourseworkforhimorherisfraudulentandwillresultinbeingdeniedcoursecompletionandcorrespondingcredithours.Thecourseproviderreservestherighttomakecontactasnecessarytoverifytheintegrityofanyinformationsubmittedorcommunicatedbythestudent.Thestudentagreesnottoduplicateordistributeanypartofthiscopyrightedworkorprovideotherpartieswiththeanswersorcopiesoftheassessmentsthatarepartofthiscourse.Ifplagiarismorcopyrightinfringementisproven,thestudentwillbenotifiedofsuchandbarredfromthecourseand/orhavehis/hercredithoursand/orcertificationrevoked.Communicationonthemessageboardorforumshallbeofthepersoncompletingallcoursework.

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DefinitionofTermsFoundationwallsandpiersinsmallresidentialbuildingsareusuallymadeofmasonryandshouldbeinspectedforcracking,deterioration,moisturepenetration,andstructuraladequacy.

Thefoundationbedmaybecomposedofsolidrock,sand,gravel,orunconsolidatedsandorclay.Rock,sandandgravelarethemostreliablefoundationmaterials.UnconsolidatedsandandclayarecommoninmanyareasoftheUnitedStates,butarenotasdesirableforfoundationsbecausetheyaresubjecttoslidingandsettling.

Thefootingdistributestheweightofthebuildingoverasufficientareaofgroundtoensurethatthefoundationwallswillstandproperly.Footingsareusuallyconcrete;however,inthepast,woodandstonehavebeenused.Someolderhouseswereconstructedwithoutfootings.Althoughitisusuallydifficulttodeterminetheconditionofafootingwithoutexcavatingthefoundation,afootinginastateofdisrepair,orthelackofafooting,willusuallybeindicatedeitherbysettlementinthefoundationwallsorbylargecracks.Thesecracksarecalled“Z”cracks.Thefoundationwallssupporttheweightofthestructureandtransferthisweighttothefootings.Thefoundationwallsmaybemadeofstone,brick,concrete,orconcreteblocks.Theexteriorshouldbemoisture-proofedwitheitheracoatingofPortlandcementmortaroramembraneofwaterproofmaterial.Themembranemayconsistofplasticsheeting,orasandwichofstandardroofingfeltjoinedandcoveredwithtarorasphalt.Waterproofingthefoundationandwallswillpreventwaterfrompenetratingthewallmaterialandleavingthebasementorcellarwallsdamp.

Masonry

Allexposedmasonryshouldbeinspectedforcracking,spalling,bowing(verticalbulging),sweeping(horizontalbulging),leaning,andmortardeterioration.Beforebeginningadetailedmasonryinspection,determinewhichwallsareload-bearingandwhicharenot.Usually,thiscanbedonebyexaminingthebeamsandjoistsinthebuilding’sbasement,crawlspaceorattic.Alsonotewhetherthewallsaresolidmasonryormasonry-cavity,non-structuralbrick,orstoneveneer.Theoverallqualityofthebuilding’sconstruction,andoftenthatofitsneighborhood,willbeagoodindicatoroftheconditionofitsmasonry.

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Mostcommonmasonrywallcrackshaveprobablybeencausedbythermalormoistureexpansion.Activecrackscanbesealedwithaflexiblesealant;inactivecracksmaybepointed.

Theremaybeasubstantialdifferenceinthemasonrywallsinbuildingsbuiltduringthelast40to50yearscomparedtothoseconstructedearlier.Wallsbecamethinnerasdesignersbegantomoreeffectivelyexploitthecompressivestrengthofmasonry.Thiswasdonebyusinghigherstrengthmasonrymaterialsandmortars.Thischangecameattheexpenseofflexibility;assuch,wallsareoftenmorebrittlethantheirmassiveancestorsand,therefore,moresubjecttostress-induceddamage.

Testing

Twomethodsoftestingaresometimesusefulforassessingmasonry.Probeholesaredrilledthroughthejointsormasonryunitswithamasonrybitandprobedwithastiffwire(or,ifavailable,afiberopticdevice)todetermineawall’sthicknessandtheadequacyofitsmortar.Theprobeholesarethenpatchedaftertheinvestigationhasbeencompleted.

Ahammertestcanbeusedtodeterminethestructuralsoundnessofmasonryunitsandtheirbondtothemortar.Inahammertest,themasonryistappedlightlywithahammer,andtheresonanceofthesoundproducedisevaluated.

Twoadditionaltestsmayalsobeuseful:ASTME518,theStandardTestMethodsforFlexuralBondStrengthofMasonry;andASTME519,theStandardTestMethodforDiagonalTension(Shear)inMasonryAssemblages.Thesetestshouldbeperformedbyaqualifiedmasonrycontractor.

Thebrickshownhereisgreatlyspalledasaresultofexcessivemoisturepenetrationandsubsequentfreezing.Althoughindividualbrickscanbereplacedandthemortarpointed,thedamagecannotberepaired.Ifrepointed,thenewmortarshouldbeofthesamecompositionastheexisting.

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MasonryCracks

Althoughmasonrycandeformelasticallyoverlongperiodsoftimetoaccommodatesmallamountsofmovement,largemovementsnormallycausecracking.Thisisknownasmasonrycracking.

Cracksmayappearalongthemortarjointsorthroughthemasonryunits.Crackingcanresultfromavarietyofproblems:

• differentialsettlementoffoundations;• dryingshrinkage(particularlyinconcreteblock);• expansionandcontractionduetoambientthermalandmoisturevariations;• impropersupportoveropenings,theeffectsoffreeze-thawcycles;• thecorrosionofironandsteelwallreinforcement;• differentialmovementbetweenbuildingmaterials;• expansionofsalts;and• thebulgingorleaningofwalls.

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DifferentialSettlementCausedbyVariableSoilTypes

Cracksshouldalwaysbeevaluatedtodeterminetheircauseandwhethercorrectiveactionisrequired.Lookforsignsofmovement.Acleancrackindicatesrecentmovement;adirtyorpreviouslyfilledcrackmaybeinactive.Apocketlensmaybeusefulforsuchanexamination.

Correlatethewidthoflargercrackstotheageofthebuilding.A1/2-inchcrackinanewbuildingmaybeasignofrapidsettlement,butinabuilding50yearsold,itmayindicateaveryslowmovementofonly1/100ofaninch(0.25mm)peryear.Ineachcase,thecauseandtreatmentmaydiffer.

Testing

Crackmovementcanbemeasuredwithacommerciallyavailablejointmovementindicator.Thisdeviceistemporarilyfastenedoverthecrackandascriberecordsmovementoveraperiodoftime.Cyclicalmovementsmaytakesixmonthsormoretomeasure,butdiurnalmovementscanberecordedoverafewdays.Handmeasurementscanalsobemadeofcrackmovements,butthesewillbelesspreciseandrequirerepeatedfieldvisits.Alltestsshouldbeperformedbyalicensedcontractor.

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EvidenceofFrost-Heaving

Cracksassociatedwiththermalexpansionandcontractionmayopenandclosewiththeseason.Thesearecyclicalcracks,whichmaygraduallyexpandasaccumulatingmortardebrisjamsthemfartherapartaftereachcycle.Suchcracksshouldbecleanedandprotectedbyflexiblesealants.Re-mortaringcyclicalcrackswillholdthemopenandcausemorecracking.Whentherearemasonryproblems,itisadvisabletorecommendtheservicesofastructuralengineer.Ifproblemsappeartobeduetodifferentialsettlement,asoilengineeralsomayberequired.

Thephotoaboveshowsanextremecaseofstructuralfailureinamasonrywallduetofoundationsettlement.Thewallandfoundationmustbecompletelyrebuilt.BricksandMortar

Thetwoimportantqualitiesofmortarareitsabilitytobondtomasonryanditsinternalstrength.Asignofmortardeteriorationmayberandomcrackingatthebondjoint.Until

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abouttheendofthe19thcentury,thestandardmortarformasonrywasamixtureofsandandpurelimeorlime-possolan-sand.Theselow-strengthmortarsgavemasonrytheabilitytoabsorbconsiderablestrain.Accordingly,thetendencytocrackwasreduced,andwhencracksdidappearinthemortarjoints,theywere,toagreatextent,capableofchemicalreconstitution,or“self-healing.”Thus,theageofthebuildingmaybeagoodclueinevaluatingitsmortarproblems.Oldermortar(ormortarofanyagethatuseshydratedlime)willbesofterandmayrequirepointing,butotherwisemayberesponsibleforasoundwall.Mostoften,mortardeteriorationisfoundinareasofexcessivemoisture,suchasnearleakingdownspouts,belowwindows,andatthetopsofwalls.Insuchcases,thewatershouldberedirectedandthejointsshouldberepointed.Pointingshouldbeperformedwithmortarofacompositionsimilartoorcompatiblewiththeoriginalmortar.Theuseofhigh-strengthmortartopointmortarofalowerstrengthcandoseriousdamagetothemasonry,sincethepointingcan’t“flexwith”oractinasimilarwaywiththerestofthejoint.

Itisusefultorememberthatmortaractsasadrainagesystemtoequalizehydrostaticpressurewithinthemasonry.Nothingshouldbedonetoreduceitsporosityandtherebyblockwaterflowtotheexteriorsurface.

Testing

Todeterminethecompositionofexistingmortar(thepercentageoflimeandothermaterials),asamplecanberemovedandchemicallyanalyzedbyatestinglaboratory.Thisshouldbedonebyaqualifiedstructuralengineer.Thedeteriorationofmasonryunitsintheformofspalling,dusting,orflakingofbrickmaybeduetoeithermechanicalorchemicaldamage.Mechanicaldamageiscausedbymoistureenteringthebrickandfreezing,resultinginspallingofthebrick’souterlayers.Spallingmaycontinueormaystopofitsownaccordaftertheouterlayersthattrappedtheinteriormoisturehavebrokenoff.Chemicaldamageiscausedbytheleachingofchemicalsfromthegroundintothebrick,resultingininternaldeterioration.Externalsignsofsuchdeteriorationareadustingorflakingofthebrick.

Verylittlecanbedonetocorrectexistingmechanicalandchemicaldamage,withtheexceptionofreplacementofthebrick.Mechanicaldeteriorationcanbeslowedorstoppedbydirectingwaterawayfromthemasonrysurfaceandbypointingmortarjointstoslowwaterentryintothewall.Surfacesealants(damp-proofingcoatings)arerarelyeffective,andmayhastendeteriorationbytrappingthemoistureand/orsolublesaltsthatinevitablypenetratethewalland,inturn,causefurtherspalling.Chemicaldeteriorationcanbeslowedorstoppedbyaddingadamp-proofcourseintothebrickwalljustabovethegroundline,orbyinjectingadamp-proofingmaterialintothesamearea.Recommendamasonryspecialistforthistypeofrepair.

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Above-GroundMasonryWalls

Inspectabove-groundstone,brick,andconcrete-blockwallsforsignsofthefollowingproblems:

• brick-wallcrackingassociatedwiththermalandmoisturemovement:Above-groundbrickwallsexpandinwarmweather(particularlyiffacingsouthorwest),andcontractincoolweather.Thiscreatesstressinthewallsthatmaycauseavarietyofcrackingpatterns,dependingontheconfigurationofthewallandthenumberandlocationofopenings.Suchcracksarenormallycyclicalandwillopenandclosewiththeseason—theywillgrowwiderincoldweatherandnarrowerinhotweather.Lookforcrackingatthecornersoflongwalls,wallswithabruptchangesincross-section(suchasatarowofwindows),wallswithabruptturnsorjogs,andintransitionsfromone-totwo-storywalls.Thesearetheweakpointsthathavetheleastcapacityforstress.Commonmoistureandthermalmovementcrackingincludes:

o horizontalordiagonalcracksnearthegroundatpiersinlongwallsduetohorizontalshearingstressesbetweentheupperwallandthewallwhereitenterstheground.Theupperwallcanthermallyexpand,butitsmovementatgroundlevelismoderatedbyearthtemperatures.Suchcracksextendacrossthepiersfromoneopeningtothenextalongthelineofleastresistance.Thisconditionisnormallyfoundonlyinwallsofsubstantiallength.

o verticalcracksneartheendwallsduetothermalmovement.Acontractingwalldoesnothavethetensilestrengthtopullitsendwallswithitasitmovesinward,causingitortheendwallstocrackverticallywheretheymeet.

o verticalcracksinshortoffsetsandsetbackscausedbythethermalexpansionofthelongerwallsthatareadjacenttothem.Theshorterwallsare“bent”bythisthermalmovementandcrackvertically.

o verticalcracksnearthetopandendsofthefacadeduetothethermalmovementofthewall.Thismayindicatepoorlybondedmasonry.Crackswilltendtofollowopeningsupward.

o cracksaroundstonesillsandlintelscausedbytheexpansionofthemasonryagainstbothendsofatight-fittingstonepiecethatcannotbecompressed.Cracksassociatedwiththermalandmoisturemovementoftenpresentonlycosmeticproblems.Aftertheircausehasbeendetermined,theyshouldberepairedwithaflexiblesealant,sincefillingsuchcycliccrackswithmortarwillsimplycausethemasonrytocrackinanotherlocation.Cracksshouldbeexaminedbyastructuralengineerandmayrequiretheinstallationofexpansionjoints

• brickwallcrackingassociatedwithfreeze-thawcyclesandcorrosion.Brickwallsoftenexhibitdistressduetotheexpansionoffreezingwaterortherustingofembeddedmetals.Suchdistressincludes:

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o crackingaroundsills,cornices,eaves,chimneys,parapets,andotherelementssubjecttowaterpenetration,usuallyduetothemigrationofwaterintothemasonry.Thewaterexpandsuponfreezing,breakingthebondbetweenthemortarandthemasonry,andeventuallydisplacingthemasonryitself.Thepathofthewaterthroughthewallisindicatedbythepatternofdeterioration.

o crackingaroundironandsteellintelscausedbytheexpansiveforceofcorrosionthatbuildsuponthesurfaceofthemetal.Thiscorrosionexertsgreatpressureonthesurroundingmasonryanddisplacesit,sincecorrodedironcanexpandtomanytimesitsoriginalthickness.Structuralironandsteelconcealedwithinthemasonry,ifexposedtomoisture,canalsocorrodeandcausecrackinganddisplacementofitsmasonrycover.Ruststainsusuallyindicatethatcorrosionisthecauseoftheproblem.Checktomakesurethejointbetweenthemasonryandthesteellintelthatsupportsthemasonryoveranopeningisclearandopen.Ifthejointhasbeensealed,thesealantormortarshouldberemoved.Theseconditionscanusuallybecorrectedbyrepairingorreplacingcorrodedmetalcomponents,andbyrepairingandpointingthemasonry.Wherecrackingissevere,portionsofthewallmayhavetobereconstructed.Cracksshouldbeexaminedbyastructuralengineer.

Despitethelossofmasonry,thisarchisintactandcanberepairedwithmatchingbricks.

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Wallsthatextendaboveceilingjoists:

StoneFoundationWallsFieldstoneandLimestoneFoundationWalls

Fieldstoneandlimestonefoundationwallsarethemostcommonfoundationsfoundinhomesthatareapproximately100yearsoldorolder.Theywereconstructedbyusingmortartobondthestonestogetherasthestoneswerestacked.Thetypeandstrengthofmortarusedatthetimethewallwasconstructedisoftenquestionable.

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Asthesefoundationsage,themortardeteriorates,turnstopowder,andthewallslosestrength,possiblycausingthemtodevelopcracksandbowinward.Theinwardbowingiscausedbythelateralorhorizontalearthpressurepushingtheweakenedfoundationwallinward.Lateralearthpressureincreasessignificantlyasthesoilbecomessaturatedwithwater.Witholder,historichomes,thestonefoundationproblemissignificantbecauseaperimeterdrainagesystemwastypicallynotinstalled.Thisisusuallyevidentasthebasementareamayshowindicationsofmoistureintrusion.

Ifthemortarjointsaredeterioratedbutthefoundationwallisnotcrackedorbowed,andtheobjectiveistosimplyextendtheserviceablelifeofthefoundationwalls,thenasolutionmaybeassimpleascleaningandtuckpointingthemortarjoints.Ifwaterpenetrationisanissue,thentheexteriormayhavetobeexcavatedandaperimeterdrainagesysteminstalled.Atthesametimethisisdone,theexteriorofthestonefoundationwallsshouldalsobecleaned,tuckpointed,pargecoated(coveredwithalayerofmortar),andwaterproofed.Caremustbetakenwhenbackfillingstonefoundationwallssoastonotdamagethemwiththeimpactofthebackfillmaterial.

Ifthemortarjointsaredeterioratedandthewallhasdevelopedcracksorisbowedinward,thenthefoundationmayhavetobereplacedorreinforcedwithanewconcretewallinfrontofit.Unfortunatelybracingthewallwithverticalsteelbeamsisnotaviableoptionasthewallwillcontinuetobowandcrackbetweentheverticalbraces.

Foundationwallingoodcondition.

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Deterioratedlimestonefoundation.



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Deterioratedstonefoundationasseenfromtheexterior.

Foundationwallingoodcondition.Thelowerwallthatstepsinwardmayhavebeeninstalledtoraisetheroomheightandtoreinforcetheoriginalrearstonefoundationwall

anditsfoundation.

Fieldstonefoundationwallingoodcondition.

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Masonry

Masonry—brick,stone,terra-cotta,andconcreteblock—isfoundonnearlyeveryhistoricbuilding.Structureswithall-masonryexteriorscometomindimmediately,butmostotherbuildingsatleasthavemasonryfoundationsorchimneys.Althoughgenerallyconsidered"permanent,"masonryissubjecttodeterioration,especiallyatthemortarjoints.Repointing,alsoknownsimplyas"pointing"or—somewhatinaccurately—"tuckpointing",istheprocessofremovingdeterioratedmortarfromthejointsofamasonrywallandreplacingitwithnewmortar.Properlydone,repointingrestoresthevisualandphysicalintegrityofthemasonry.Improperlydone,repointingnotonlydetractsfromtheappearanceofthebuilding,butmayalsocausephysicaldamagetothemasonryunitsthemselves.

Mortarconsistingprimarilyoflimeandsandhasbeenusedasanintegralpartofmasonrystructuresforthousandsofyears.Upuntilaboutthemid-19thcentury,limeorquicklime(sometimescalledlumplime)wasdeliveredtoconstructionsites,whereithadtobeslaked,orcombinedwithwater.Mixingwithwatercausedittoboilandresultedinawetlimeputtythatwaslefttomatureinapitorwoodenboxforseveralweeks,uptoayear.Traditionalmortarwasmadefromlimeputty,orslakedlime,combinedwithlocalsand,generallyinaratioof1partlimeputtyto3partssandbyvolume.Oftenotheringredients,suchascrushedmarineshells(anothersourceoflime),brickdust,clay,naturalcements,pigments,andevenanimalhairwerealsoaddedtomortar,butthebasicformulationforlimeputtyandsandmortarremainedunchangedforcenturiesuntiltheadventofportlandcementoritsforerunner,Romancement,anatural,hydrauliccement.

PortlandCement

PortlandcementwaspatentedinGreatBritainin1824.ItwasnamedafterthestonefromPortlandinDorsetwhichitresembledwhenhard.Thisisafast-curing,hydrauliccementwhichhardensunderwater.PortlandcementwasfirstmanufacturedintheUnitedStatesin1872,althoughitwasimportedbeforethisdate.Butitwasnotincommonusethroughoutthecountryuntiltheearly20thcentury.Upuntiltheturnofthecenturyportlandcementwasconsideredprimarilyanadditive,or"minoringredient"tohelpacceleratemortarsettime.Bythe1930s,however,mostmasonsusedamixofequalpartsportlandcementandlimeputty.Thus,themortarfoundinmasonrystructuresbuiltbetween1873and1930canrangefrompurelimeandsandmixestoawidevarietyoflime,portlandcement,andsandcombinations.

Inthe1930smorenewmortarproductsintendedtohastenandsimplifymasons'workwereintroducedintheU.S.Theseincludedmasonrycement,apremixed,baggedmortarwhichisacombinationofportlandcementandgroundlimestone,andhydratedlime,machine-slakedlimethateliminatedthenecessityofslakingquicklimeintoputtyatthesite.

Thedecisiontorepointismostoftenrelatedtosomeobvioussignofdeterioration,suchasdisintegratingmortar,cracksinmortarjoints,loosebricksorstones,dampwalls,or

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damagedplasterwork.Itis,however,erroneoustoassumethatrepointingalonewillsolvedeficienciesthatresultfromotherproblems.Therootcauseofthedeterioration—leakingroofsorgutters,differentialsettlementofthebuilding,capillaryactioncausingrisingdamp,orextremeweatherexposure—shouldalwaysbedealtwithpriortobeginningwork.

Withoutappropriaterepairstoeliminatethesourceoftheproblem,mortardeteriorationwillcontinueandanyrepointingwillhavebeenawasteoftimeandmoney.

ThecontentandimagesofthisslidewerecontributedbyTheodoreJ.Carlson,LicensedStructuralEngineeratStructuralDynamicsandtheU.S.DepartmentoftheInterior.

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FireDamageFireDamagetoBrickMasonryWalls

Masonrywallsexposedtofirewillresistdamageinproportiontotheirthickness.Examinethetextureandcolorofthemasonryunitsandprobetheirmortar.Iftheyareintactandtheirbasiccolorisunchanged,theycanbeconsideredserviceable.Iftheyundergoacolorchange,recommendaqualifiedstructuralengineerforfurtherappraisal.Hollowmasonryunitscanbeexaminedbyastructuralengineerforinternalcracking.Suchunitsmayneedreplacementifseriouslydamaged.Masonrywallsplasteredonthesideindirectcontactwithflamemayhavebeensufficientlyprotectedandwillhavesufferedfew,ifany,illeffects.

StructuralFailure

WallCrackingorDisplacementAssociatedwiththeStructuralFailureofBuildingElements

Problemsrelatedtothestructure,asidefromthosecausedbydifferentialsettlementorearthquakes,areusuallyfoundoveropeningsand(lesscommonly)underroofeavesandinareasofstructuraloverloading.Suchproblemsinclude:

•crackinganddisplacementofmasonryoveropenings,resultingfromthedeflectionandfailureofthelintelsandarchesthatspantheopenings.Inoldermasonrywallswithwoodlintels,crackingwilloccurasthewoodsagsanddecays.Ironandsteellintelsalsocausecrackingastheydeflectovertime.Concreteandstonelintelsoccasionallybowandsometimescrack.

Masonryarchesofbrickandstonemaycrackandfailwhenthereiswallmovementandwhentheirmortarjointsdeteriorate.Whensuchlinteldeflectionsandarchfailuresoccur,themasonryabovemaybesupportingitselfandwillexhibitstepcracks,beginningattheedgesoftheopeningandjoininginaninverted“V”abovetheopening’smidpoint.Correctingsuchproblemsusuallymeansreplacingfailedcomponentsandrebuildingtheareaabovetheopening.

Occasionally,masonryarchesfailbecausethewallsthatsurroundthemcannotprovideanadequatecounter-thrusttothearchaction.Thissometimeshappensonwindowsthataretooclosetothecornersofawallorbay.Insuchcases,themasonryarchpushestheunbracedwalloutward,causingittocrackabovetheopeningnearorjustabovethespring

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ofthearch.Whenthisoccurs,theendwallsmustbestrengthened.•crackingoroutwarddisplacementundertheeavesofapitchedroofduetoafailureinthehorizontalroofties,whichresultsintheroofspreadingoutward.Thelateralthrustoftheroofonthemasonrywallmaycauseittocrackhorizontallyjustbelowtheeaves,ortomoveoutwardwiththeroof.Inthiscase,theroofwillprobablybeleaking,aswell.Whenthisoccurs,examinetheroofstructurecarefullytoascertainwhetherthereisatyingfailure.Ifso,additionalhorizontaltiesortensionmemberswillhavetobeaddedand,ifpossible,theroofpulledbackintoplace.Thedamagedmasonrycanthenberepaired.Theweightalsocanbetransferredtointeriorwalls.Jackingoftheridgeandraftersisanotherpossiblesolution.•crackingduetooverloading(orinteriormovement)isfairlyuncommon,butmaybecausedbyapointload(oftenaddedduringanalteration)whichisbearingonawallofinsufficientthickness.Ifthememberhasbeenconcealed,suchaproblemwillbedifficulttoinvestigate.Theadditionofinteriorwallsupportsorbracing,however,maycorrectthesourceoftheproblembyrelievingtheload.•crackingduetogroundtremorsfromnearbyconstruction,heavyvehiculartraffic,orearthquakes.Thiscrackingisroughlyverticalindirectionandoccursmoretowardthecenterofthebuilding.Buildingsexhibitingsuchcrackingshouldbetreatedonacase-by-casebasis,sinceseriousstructuraldamagemayhavetakenplace.Recommendastructuralengineerexperiencedinsuchmatters.

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BulgingWalls

Masonrywallssometimesshowsignsofbulgingastheyage.Awallitselfmaybulge,orthebulgemayonlybeintheouterwythe.Bulgingoftentakesplacesoslowlythatthemasonrydoesn’tcrackand,therefore,itmaygounnoticedoveralongperiodoftime.Thebulgingofthewholewallisusuallyduetothermalormoistureexpansionofthewall’soutersurface,orduetocontractionoftheinnerwythe.Thisexpansionisnotcompletelyreversiblebecause,oncethewallanditsassociatedstructuralcomponentsare“pushed”outofplace,theycanrarelybecompletely“pulled”backtotheiroriginalpositions.

Theeffectsofthecyclicalexpansionofthewallarecumulativeand,aftermanyyears,thewallwillshowadetectablebulge.Insidethebuilding,separationcrackswilloccurontheinsidefaceofthewallatfloors,wallsandceilings.Bulgingofonlytheoutermasonrywytheisusuallyduetothesamegradualprocessofthermalormoistureexpansion;masonrydebrisaccumulatebehindthebulgeandpreventthecoursefromreturningtoitsoriginalposition.Inveryoldbuildings,smallwallbulgesmayresultfromthedecayandcollapseofaninternalwoodlintelorwood-bondingcourse.Thiscancausetheinnercoursetosettleandtheoutercoursetobulgeoutward.Whenwallbulgesoccurinsolidmasonrywalls,thewallsmaybeinsufficientlytiedtothestructure,ortheirmortarmayhavelostitsbondstrength.Largebulgesmustbetiedbacktothestructure;thestar-shapedanchorsontheexteriorofmasonrywallsofmanyolderbuildingsareexamplesofsuchties(checkwithlocalbuildingordinancesontheiruse).Smallbulgesintheoutermasonrycourseoftencanbepinnedtotheinnercourseordismantledandrebuilt.

TheV3RuleforWallStabilityLeaningWalls

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Masonrywallsthatlean(invariablyoutward)representaseriousifuncommonconditionthatisusuallycausedbypoordesignandconstructionpractices,particularlybyinadequatestructuraltyingorpoorfoundationwork.Whentiltingorleaningoccurs,itisoftenassociatedwithparapetsandotherupperwallareas,especiallythosewithheavymasonrycornicescantileveredfromthewall.Leaningcanproduceseparationcrackingontheendwallsandcrackingontheinteriorwallfacealongfloors,wallsandceilings.Leaningwallscansometimesbetiedbacktothestructureand,thereby,restrained.Insuchcases,thebearingandconnectionsofinteriorbeams,joists,floorsandroofshouldbeexamined.

Above:abowedbrickveneerwall

Whenlargeareasorwholewallslean,rebuildingthewall(andpossiblythefoundation)maybetheonlyanswer.

Testing

Awallisusuallyconsideredunsafeifitleanstosuchanextentthataplumblinepassingthroughitscenterofgravitydoesnotfallinsidethemiddlethirdofitsbase(theV3Rule).Insuchanevent,recommendastructuralengineer.

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Quiz1T/F:A50-yearoldbuildingthathasa1/2-inch-widecrackthathasbeenpresentforyearsisasignofrapidsettlement.

• False• True

Foundationwallsandpiersinsmallresidentialbuildingsareusuallymadeof_____________.

• masonry• steel• preservative-treatedwood

Afootingindisrepaircanleadto_______inthefoundationwalls.

• Z-cracks• pockmarks• chipping

T/F:Rock,sandandgravelarethemostreliablefoundationmaterials.

• True• False

Verticalbulginginthemasonryisknownas_________.

• bowing• sweeping• spalling

Horizontalbulginginthemasonryisknownas____________.

• sweeping• bowing• spalling

Ina________test,themasonryistappedlightlyandtheresonanceofthesoundproducedisevaluated.

• hammer• hearing• hacksaw

Excessivemoisturepenetratingandsubsequentfreezingcanleadto_________.

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• spalling• forking• spleening

T/F:Cyclicalcracksshouldbere-mortared.

• False• True

Masonrywallsexposedtofirewillresistdamageinproportiontotheir_________.

• thickness• age• height

Innovations:CementAdmixturesAdmixturesarematerialsotherthancement,aggregateandwaterthatareaddedtoconcreteeitherbeforeorduringitsmixingtoalteritsproperties,includingitsworkability,curingtemperaturerange,settime,orcolor.Someadmixtureshavebeeninuseforaverylongtime,suchascalciumchloride,whichisusedtoprovideacold-weathersettingconcrete.Othersaremorerecentandrepresentanareaofexpandingpossibilitiesforincreasedperformance.Notalladmixturesareeconomicaltouseonaparticularproject.Also,somecharacteristicsofconcrete,suchaslowabsorption,canbeachievedsimplybyconsistentlyadheringtohigh-qualityconcretingpractices.

Thechemistryofconcreteadmixturesisacomplextopicrequiringin-depthknowledgeandexperience.Ageneralunderstandingoftheoptionsavailableforconcreteadmixturesisnecessaryforacquiringtherightproductforthejob,basedonclimaticconditionsandjobrequirements.

Basedontheirfunctions,admixturescanbeclassifiedintothefollowingfivemajorcategories:•retardingadmixtures;•acceleratingadmixtures;•super-plasticizers;•water-reducingadmixtures;and•air-entrainingadmixtures.Amongotherimportantadmixturesthatdonotfitintothesecategoriesareadmixtureswhosefunctionsincludebonding,shrinkagereduction,damp-proofing,andcoloring.Thefollowinginformationprovidesdetailsonthefivecategoriesofconcreteadmixtures.

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RetardingAdmixturesRetardingadmixturesslowdownthehydrationofcement,whichlengthensitssettime.Retardersareusedinhot-weatherconditionsinordertoovercometheacceleratingeffectsofhighertemperatures,andonlargemassesofconcretetolengthensettingtime.Becausemostretardersalsoactaswaterreducers,theyarefrequentlycalledwater-reducingretarders.PerthechemicaladmixtureclassificationbytheASTM,ASTMC494,TypeBissimplyaretardingadmixture,whileTypeDisbothretardingandwater-reducing,resultinginconcretewithgreatercompressivestrengthbecauseofthelowerwater-to-cementratio.Retardingadmixturesconsistofbothorganicandinorganicagents.Organicretardantsincludeunrefinedcalcium,sodium,NH4,saltsoflignosulfonicacids,hydrocarboxylicacids,andcarbohydrates.Inorganicretardantsincludeoxidesofleadandzinc,phosphates,magnesiumsalts,fluoratesandborates.

Anexampleofaretardant'seffectsonconcretepropertiesincludeslignosulfateacidsandhydroxylatedcarboxylicacids,whichslowtheinitialsettingtimebyatleastanhour,andnomorethanthreehours,whenusedat65°to100°F.Theconcretecontractor,however,neednotmemorizethesechemical-specificresults.Giventhespecificjobrequirementsandgoals,theconcretesuppliershouldofferappropriateadmixturesandconcretemixesfromwhichtochoose.

AcceleratingAdmixturesAcceleratorsshortenthesettimeofconcrete,allowingacold-weatherpour,earlyremovalofforms,earlysurfacefinishingand,insomecases,earlyloadapplication.Propercaremustbetakenwhilechoosingthetypeandproportionofacceleratorsas,undermostconditions,commonlyusedacceleratorscauseanincreaseinthedryingshrinkageofconcrete.Calciumchlorideisacommonacceleratorusedtoacceleratethetimeofsetandtherateofstrength-gain.ItshouldmeettherequirementsofASTMD98.Excessiveamountsofcalciumchlorideinconcretemixmayresultinrapidstiffening,increaseindryingshrinkageandcorrosionofreinforcement.Incolderclimates,calciumchlorideshouldnotbeusedasananti-freeze.Largeamountsofcalciumchloridearerequiredtolowerthefreezingpointoftheconcrete,whichmayruintheconcrete.

Super-PlasticizersSuper-plasticizers,alsoknownasplasticizers,includewater-reducingadmixtures.Comparedtowhatiscommonlyreferredtoasa"waterreducer"or"mid-rangewaterreducer,"super-plasticizersare"high-rangewaterreducers."High-rangewaterreducersareadmixturesthatallowlargewaterreductionorgreaterflowabilitywithoutsubstantiallyslowingsettimeorincreasingairentrainment(asdefinedbythemanufacturers,concretesuppliersandindustrystandards).

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Eachtypeofsuper-plasticizerhasdefinedrangesfortherequiredquantitiesofconcretemixingredients,alongwiththecorrespondingeffects.Theycanmaintainaspecificconsistencyandworkabilityatagreatlyreducedamountofwater.Amountsneededvarybytheparticularconcretemixandtypeofsuper-plasticizerused.Theycanalsoproduceahigh-strengthconcrete.Aswithmosttypesofadmixtures,super-plasticizerscanaffectotherconcreteproperties,aswell.Thespecificeffects,however,shouldbeprovidedbythemanufacturerorconcretesupplier.

Water-ReducingAdmixturesWater-reducingadmixturesrequirelesswatertomakeaconcreteofequalslumporincreasedslumpatthesamewatercontent.Theycanhavethesideeffectofchanginginitialsettime.Waterreducersaremostlyusedforhot-weatherconcreteplacing,andtoaidpumping.Awater-reducerplasticizer,however,isahygroscopicpowder,whichcanentrainairintotheconcretemixviaitseffectonwater'ssurfacetension,therebyobtainingsomeofthebenefitsofair-entrainment.

Air-EntrainingAdmixturesAir-entrainingagentsentrainsmallairbubblesintheconcrete.Themajorbenefitofthisisenhanceddurabilityinfreeze-thawcycles,whichisespeciallyimportantincoldclimates.Whilesomestrengthcanbelostwithincreasedairinconcrete,itcangenerallybeovercomebyreducingthewater-to-cementratioviatheimprovedworkabilitymadepossiblebytheair-entrainingagent,orthroughtheuseofotherappropriateadmixtures.Asalways,admixturesshouldonlybecombinedinaconcretemixbyacompetentprofessional,becausesomeoftheadmixturescaninteractinundesirableways.

OtherAdmixtures

Bondingadmixtures,includingtheadditionofcompoundsandmaterialssuchaspolyvinylchloridesandacetates,acrylics,andbutadiene-styreneco-polymers,canbeusedtoassistinbondingneworfreshconcretewitholdorsetconcrete.Coloringagentshavebecomemorecommonlyused,especiallyforpatiosandwalkways.Mostaresurface-applied,andoftenhavetheadditionaleffectofsurfacehardening.Suchsurface-appliedcoloringadmixturesgenerallyshouldnotbeusedonair-entrainedconcrete.Integrallycoloredconcreteisalsoavailable.Waterproofinganddamp-proofingadmixtures,includingsoaps,butylstearate,mineraloilandasphaltemulsions,areusedtodecreasetheamountofwaterpenetrationintothelargerporesofconcrete."Antifreeze"admixturesareacceleratorsusedinveryhighamounts(withacorrespondinghighprice)whichachieveaveryfastsettime.Theydonot,however,havepropertiestoprotectagainstfreezing.Ingeneral,thesearenotusedforresidentialwork.

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Cementsubstitutesalsochangeconcreteproperties,butarenotgenerallyclassifiedasadmixtures.Mostorganicchemical-typeadmixturesareaffectedbycementtypeandbrand,water-to-cementratio,aggregategrading,andtemperature.Damp-proofingandwaterproofingadmixturesstillhaveuncertainvalueandhazards.Thesearejusttwocasesthatpointtothelearningcurverequiredofanyoneworkingwithadmixtures.

UsingAdmixtures

Insomecases,ifdirectionsarenotfollowedexactly,includingtheadditionofsupplementalmaterialstobalancethenegativeorundesirablesideeffectsofanadmixture,theresultingconcretemixmaybecompromised.Forexample,retardingadmixturesgenerallyhaveapossibilityofrapidconcretestiffening,resultingindifficultyinplacementandfinishing.Therefore,anin-depthknowledgeofthepotentiallycomplexinterrelatedeffectsisrequiredtouseanumberofadmixturessuccessfully.Thisisevenmorecriticalwhenseveralpartiesareinvolvedinthemanufactureoftheconcrete,suchastheproducer,theplacingcontractor,andthebuilder.Thefinishedconcreteisacombinedresultofanumberofindividualdecisions.Choosinganappropriateadmixtureforaspecificjobshouldbetheresponsibilityofanexperiencedexpert.Alternativestotheuseofadmixturesshouldalwaysbeconsidered.Theenvironmentalimpactofcertainadmixturesisquestionable.Somesuper-plasticizersmayimpacttheenvironmentthroughpollutionofgroundandsurfacewaters.Moreresearchremainstobeconductedinthisarea.Finally,admixturescannotcompensateforpoorworkmanshiporlow-qualitymaterials.

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Innovations:CementSubstitutes

Producingcementusesagreatdealofenergy,sofindingawasteproductthatcansubstituteforcementmakesgoodenvironmentalsense.AccordingtotheEnvironmentalBuildingNews(EBN),asmuchgreenhousegasiscreatedproducingthePortlandcementusedintheU.S.asiscreatedoperating22millioncompactcars.Inaddition,theU.S.importsabout20%ofthe100millionmetrictonsofcementitusesannually,addingtoitscostandusingmoreenergy.Burningcoaltomakeelectricpowercreatesagreatdealofwasteflyash.Asmalleramountofslagiscreatedwhenproducingironinblastfurnaces.Coalflyash,blast-furnaceslagandothermineraladmixturescansubstituteforcementinconcretemixesforbuildingswhichwillsaveenergyandrecycleawasteproduct,therebyimprovingthequalityoftheconcreteandreducingcosts.Cementsubstitutesshouldbedistinguishedfromconcreteadditives,suchasplasticizersandair-entrainmentagents,andfromaggregatesubstitutes,suchasgroundglassorgroundscraprubber.

TypesofCementSubstitutesFlyashisoneofthebyproductsofburningcoaltocreateelectricpower.Two-thirdsofthe55milliontonsofflyashproducedintheU.S.in1999wassenttowastepiles,withonly9milliontonsusedtomakeconcrete.Thecarboncontentofflyashisamajorconcern.ClassCflyash,mostofwhichisproducedintheWestfromlignitecoal,containslittlecarbon.However,ClassFflyash,producedprimarilyfromanthraciteandbituminouscoal,containssignificantamountsofcarbon.ClassCandClassFmaterialsalsodifferfromsourcetosourcewithregardtostrength,rateofstrength-gain,color,andweatherability.Ensuringaconsistentsupplyisaconcernamongconcretesuppliers.Slagisabyproductoftheproductionofbothironandsteel,andgroundironslagfromblastfurnacescanbeusedformakingconcrete.About12.4milliontonsofblast-furnaceslagwasusedintheU.S.in1999,ofwhich2milliontonswereusedinconcrete.Inaddition,another1.1milliontonswereimportedforusebytheconstructionindustry.Becausethedemandfortheproductisrisingwhilethesupplyisfalling,newgrindingplantsarecomingonlinetoprocessimportedslag.Theaddedenergyusedtoshipandgrindtheslagmakesitsomewhatlessenergy-savingthanflyash,butfarbetterthanPortlandcement.Silicafumewasonceacheapwasteproduct,buthighdemandhasmadeitahigh-costadmixtureusedprimarilyforbridgesandotherstructureswheretopweatheringperformanceandhighstrengthareneeded.Concretemadefromsilicafumeisexpensive,however,notonlybecauseofthematerialcost,butbecausethepowderyfinenessofthefumemakesithardtohandle.Itisoftenturnedintoslurrybeforeuse.Aslongasqualityiscontrolled,ricehullashisanothermaterialthatcanbeusedtoreplacecement.Sofar,itsuseremainsinthelaboratorystage,althoughaconsistent-qualityashneededforconcreteisavailable.

SlowStrength-Gain

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Generally,cementsubstitutesworkintwoways.First,theyhydrateandcurelikePortlandcement.Second,theyare"pozzolans,"providingsilicathatreactswithhydratedlime,anunwantedbyproductofconcretecuring.Blast-furnaceslagismostlikePortlandcementandleastlikeapozzolan.ClassFflyashismostlikeapozzolan,andClassCflyashissomewhereinthemiddle.Whilestrongerandmoredurableintheend,ittakesmoretimethanPortlandcementforpozzolanstogainstrength.Formostconstructionpurposes,highearlystrengthisverydesirablebecauseitallowsquickerfinishingofslabsandearlierremovalofforms.Reducingtheamountofwatercancompensateforslowstrength-gain.Researchershavemadeconcreteinthelabfromhighpercentagesofcementsubstitutebydrasticallyreducingthewatercontentandaddingsuperplasticizerstomaintaintherequiredslump,butsuchmixesarenotyetcommonandmaybecostly.Mixeswith15%to25%flyashandsomewhathigherpercentagesofslagcanbeusedinhomebuildingwithonlyamodestslowingofstrength-gain.Higherpercentagescanbeusedinfootings,wherehighearlystrengthistypicallynotimportant.Precastersandconcretemasonryunit(CMU)producerscanmaintainprecisecontrolofthemix,andusemoreadmixtures.However,theyrequirehighearlystrengthforfastre-useofforms,soprecastconcreteseldomhashighpercentagesofcementsubstitutes.

Air-EntrainmentandCarbonContentSomeflyash,andmostoftheClassFflyashusedintheEast,containshighlevelsofcarbon,whichareunburnedcoalparticlesresultingfromthelower-temperatureburning(low-NOx)thatimprovesairquality.Carbonparticlesabsorbthesoapyair-entrainingchemicalsusedtoimprovecold-weatherperformance,and,inthisway,maketheaircontentunpredictable.ThisproblemhasledsomeNorthernsupplierstosubstituteslagadmixtureforflyash,sinceslagcontainsnocarbon.Theflyashindustryisaddressingthisproblembyprocessinghigh-carbonflyashtoremovemostofthecarbon.Concretewithmineraladmixturesmayrequiremoreair-entrainingchemicalstoensurefreeze-thawprotectionbecausethesmallparticlesofthesemineralscanfillvoidsintheconcretethatwouldotherwisebeairbubbles.

StrengthStrengthisimprovedbythesubstitutionofsomemineraladmixturesforPortlandcement.ClassCflyashandslagimprovestrengthmorethanClassFflyash.Inapplicationswherehighstrengthiscritical,suchasinhigh-risebuildings,silicafumeisthecementsubstituteofchoice,resultingincompressivestrengthsof15,000psiandhigher.

ColorClassCflyashresultsinabuff-coloredconcrete;ClassFisadarkergray.Slagconcreteislighterincolor,withhighreflectivity.Duringcuring,slagconcretemayshowablue-greenmottling,called"greening."However,thecolorisusuallygonefromthesurfaceinaweek.Itsdisappearancedependsonoxidation,soslagcementisnotrecommendedforswimmingpools.

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WeatherabilityTherearethreeweatherabilityconditionsthatcementsubstituteshelpalleviate:•permeabilityandchloride-inducedcorrosion:De-icingsaltscanmigratethroughporesintheconcrete,breakdownthepassiveprotectivelayeraroundthere-steel,andcausecorrosionthatleadstospalling.Thepozzolanicactionofcementsubstitutesremovesthecalciumhydroxidethatmakestheconcretepermeableand,therefore,ishighlydesirableinroadways.Ahighpercentageofflyashisnotrecommendedforslabsandpavingexposedtotheweatherbecauseofdustingandscalingofthesurface.•alkali-silicareaction(ASR):High-silicaaggregatesandhigh-alkalicement(whichisbecomingmorecommon)cancreateASR,whichcausesinternalexpansionandcrazingofconcrete.Cementsubstitutes,especiallyslag,removethealkalinitythroughpozzolanicaction.ClassCflyashvariesinthisability,whileClassFflyashisveryeffective.•sulfateattack:Concretemadewith60%ormoreslagisveryeffectiveinmitigatingattackbysulfatesfoundinsomearidsoils,seawaterandwastewater.Thepozzolanicactionofflyashalsocontributestosulfateresistance.Althoughthefederalgovernmentandtheheavy-constructionindustryhaveusedcementsubstitutesfordecades,residentialcontractorsarelessfamiliarwiththeiruse.Astheflyashindustrydevelopsprocessestoremovecarbon,variationsinthecompositionofflyashwillbecomelessimportant,anditspopularitywillrise.TheU.S.blast-furnaceslagsupplyisdecliningandthedemandgrowing,sofuturegrowthinitsusedependsonimports.Silicafumeremainscostlyanddifficulttohandle,andricehullashandotherpotentialsubstitutesarenotyetbeingmarketed.

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PrecastConcreteFoundationandWallPanels

Precastconcretefoundationandwallpanelscantakemanyforms.Someconsistofsteel-reinforcedconcreteribsthatrunverticallyandhorizontallyinthepanels.Othersaresolidprecastconcretepanels.Panelsareprecastandcuredinacontrolledfactoryenvironmentsothatweatherdelayscanbeavoided.Atypicalpanelizedfoundationcanbeerectedinfourtofivehours,withouttheneedtoplaceconcreteon-siteforthefoundation.Theresultisafoundationthatcanbeinstalledinanyclimatezoneinone-sixththetimeneededforaformedconcretewall.

Somemanufacturerscasttheconcreteagainstfoaminsulationthatprovidestheformduringmanufacture,andaddsR-valueinthewall.Panelsrangeinsizefrom2to12feetinwidthby8to12feetinheight,andaretypicallyinstalledwithacraneontopof4to6inchesofcompactedstone.Thestonefacilitatessub-slabdrainage,andadequatelycarriesandtransferstheloadfromthefoundationwall.Panelconnectionsconsistofboltsandsealant.Thefoundationcanbeback-filledassoonasitisbraced,perthemanufacturer'sspecifications.Thecontrolledtemperatureoftheprocessingplantallowsthemanufacturertoworkwithconcreteadmixturesthatfocusonultimatestrengthratherthancuretimeandtemperature.Manufacturersareabletoproducemixesthathardento5,000psi,whichisstrongerthanconcreteblockandconcretewallsformedandcastinthefield.Bettercontroloftheconcretemixtureandcuringenvironmentallowstheuseoflowwater-to-cementratiosthatresultinadensematerialthatpreventswaterpenetration.

InsulatingConcreteForms(ICFs)

Concreteformshavetakenonanewshapeandpurpose.Insulatingconcreteforms(ICFs)arerigid,plasticfoamformsthatholdconcreteinplaceduringcuring,andtheyremainin

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placeafterwardtoserveasthermalinsulationforconcretewalls.Thefoamsectionsarelightweightandresultinenergy-efficient,durableconstruction.ICFsconsistofinsulatingfoam,expandedpolystyrene(EPS),andextrudedpolystyrene(XPS).Thethreebasicformtypesarehollowfoamblocks,foamplanksheldtogetherwithplasticties,and4x8panelswithintegralfoamorplasticties.ICFscanbeusedtoformvariousstructuralconfigurations,suchasastandardwall,postandbeam,orgrid.Theyprovidebackingforinteriorandexteriorfinishes.InsulationvaluesofICFwallsvarydependingonthematerialanditsthickness.TypicalinsulationvaluesrangefromR-17toR-26,comparedtoR-13toR-19formostwood-framewalls.ThestrengthofICFstructuresversuslumberdependsonconfiguration,thickness,andreinforcement.However,ICFwallsaredesignedasreinforcedconcrete,havinghighwindandseismicresistance.TherearemanyICFwalltypes.Productsaredifferentiatedbasedonthetypeofformandtheshapeoftheconcretesections.Productsarefurtherdifferentiatedbyhowformsattachtoeachother,howfinishesareattachedtothewall,insulatingvalues,foamtypes,andotherfeatures.

FormworkforVentilatedConcreteSlabs

TheformworkpicturedaboveisCupolexÒ,aninnovativemodularbuildingunitusedtocreateventilatedunder-floorcavities.Bothslab-on-gradeandstructuralslabscanbecreatedusingthisformwork.Thistechnologyisdesignedtoenhanceenergy-efficientbuildings,andcanassistineradicatingproblemsassociatedwithcontaminatedsoils.Theunder-floorcavitycanreducedampness,moldandmildew,whileprovidingventilationinalldirectionsbeneaththeslab.Thiscavitycanalsoconveyanypotentialvolatileorganiccompounds(VOCs)andpermeatinggasesfromcontaminatedsoils,includingradon,totheoutsideofthebuilding.CupolexÒismadeofpolypropyleneandmanufacturedfromnon-toxic,recycledmaterialsintoplasticmodularelements,andpre-formedinvarioussizes.Theyconnecttocomposeaself-bearingstructure,suitableforplacementofconcretetocreateaslabofvariablethickness.CupolexÒisapermanentformworkandcannotbeusedtwice.Thedistinctivedomedshapeofthemodularelementsisusedtoformconcreteslabsthatprovidean

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internalorthogonalspace,allowingforoptimumaircirculation.Theindividualelementsaredesignedtobeconnectedtooneanothertoformaself-bearingstructure,restingonapre-builtbase.CupolexÒis,therefore,readyafterinstallationforanyrequiredsteelreinforcement,andforplacementofconcrete.ContinuousspaceisavailablebeneaththearrayofCupolexÒelementsthatcanbeusedforinstallingductwork,cables,piping,andheatingandventilationsystems.Thematerialisdurable,withstandsextremetemperaturesandaging,andwillnotbreakortear.

UntilcodeapprovalsintheU.S.marketareachieved,slabsdesignedwiththeCupolexÒsystemusuallywillrequirethestamporsealofalicensedprofessionalengineer.

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Innovations:ConcreteFootingandPierForms

Therearenewalternativestoconventionalformingmethodsforconcretefootingsandpiersthatarequickerandlessexpensivethanusual.Forpointfootings,therearetwoapproaches:

•rigidplasticfootingforms;or•fabric"bag"footingforms.

Continuousstripfootingsuseaspecializedfabricformheldinplacebyatemporarystructuralsystem.Typically,astandardconstructiontubeprovidestheformforaconcretepier.However,aspecialfabricalternativecanalsoprovideasuitablepierform,whenproperlyinstalledandbraced.Plasticrigidfootingformsdiffermostlyintheirshape,thoughtherearevariablesizesavailable,aswell.Somearesimilartotheconventionalblockshape,whileothersarebell-shapedwitharoundbase.Theyhaveacircularopeningontoptoaccepttheconcrete,aswellastoconnecttotheconstructiontubesabove.

Rigidfootingformshaveribstoprovideextrastrength,andsomehavesmallholestoreleaseairduringthepour.Fabric"bag"footingformsareexactlywhattheirnameimplies.Theyareflexiblefabricsackswithacircularholeontopintowhichconcreteispoured.Theshapeofthefabricformapproximatesastandardrectangularfooting,butalledgesarerounded,withbowedsides,andtheformmaybeinstalledonandconformtounevenground.

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Forfootingsthatrequirerebarreinforcing,thereisaformsackwhichhasazippertoopenthetopofthe"bag"enoughtogetthereinforcingrodsinsidethefabricformbeforeplacingtheconcrete.

Additionally,thereisafoundationpierproductdevelopedspecificallyformanufacturedhousingthatusesfootingformbagsasakeypartofitsdesign.Fabricstripfootingformscanbeusedforlevelandstepfootings,aswellasfordeepfootings,andtheycanbeinstalledoverunevengroundandrock(ifitisstructurallyacceptabletodoso).Asimple,temporaryformmustbebuilt,towhichthefabricattachesinordertoholditsshapewhiletheconcretecures.Thisismadewithaboardoneachsidethatdefinesthetopedgeoftheformtowhichthefabricattaches,heldattherequiredheightandwidthbyaspecial"yoke"supportsystem.Longboardsthatholdthefabricinplacemustbestabilizedlaterally.Thisisachievedbyregularlyspacedmetalstakespoundedintothegroundalongeithersideoftheform.Oncetheconcretesets,therigidformworkmayberemovedandreused,whilethefabricformremainsinplace.ThereisaproprietaryfoundationpierproductcalledTheButtressÒ,whichcombinesthefabricbagwithasteelpier,andwhichhasbeendevelopedspecificallyfortheHUD-codehousingmarket.Forlargepierpads,asystemsimilartothefabricformsforstripfootingscanbeused.Thissystemessentiallyconsistsofasufficientareaoffabriclaidoutovertheground,withitssidewallsheldinplacebyatemporaryformsystemoftop-edgeboardsandmetalstakes,similartotheformdescribedforthestripfootingsystem.Fabricpierformmaterialcomesin120-footlengths,withdiametersof8inchesandlarger.Theyaretheshapeofatubewithanattachmenttabrunningdowntheirlength.Becausetheyaremadeofaflexiblefabric,theformsareflatbeforebeingfilledwithconcrete.Thefabriciseasilycuttolength.

Pumice-Crete

Pumice-Crete®isalow-densityandresource-efficientconcreteconsistingofpumiceaggregate,Portlandcement,andwater.Itisaneconomicalalternativetoconventionalbuildingmaterialsbecauseitcombinesstrengthandinsulationinoneproduct.Besidesthevarietyofdesignapplicationsforwhichitcanbeused,Pumice-Crete®isadurable,fireproof,andnoise-mitigatingmaterialthatholdsupinavarietyofclimates.Pumiceisalightweight,sponge-likevolcanicrockformedbytheexpansionofgasesduringrapidcoolingofmoltenlava.ThisglassfrothisfoundinshallowdepositsinNewMexico,Arizona,California,Oregon,WashingtonandIdaho.Duetothematerial'sinertnature,itdoesnotreactwithanyingredientsofconcreteorsteel.Withanaveragecuredweightoflessthan50poundspercubicfoot,Pumice-Crete®producesacuredstrengthof400psi(comparedto2,000psiinconcrete),withan

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insulatingvalueofR-1.5perinch(comparedtoR-0.1inconcrete).Althoughmorethan350residenceshavebeenbuiltinColoradoandNewMexicousingPumice-Crete®,noofficialfireratinghasbeenperformed.

Innovations:ConcreteAggregateSubstitutes

Conventionalconcreteaggregateconsistsofsand(fineaggregate)andvarioussizesandshapesofgravelandstones.However,thereisagrowinginterestinsubstitutingalternativeaggregatematerialslargelyasapotentialuseforrecycledmaterials.Thereissignificantresearchonmanydifferentmaterialsforaggregatesubstitutes,suchasgranulatedcoalash,blast-furnaceslag,andvarioussolidwastes,includingfiberglasswastematerials,granulatedplastics,paperandwoodproductsandwaste,sinteredsludgepellets,andsimilarmaterials.However,theonlytwomaterialsthathavebeensignificantlyappliedareglassculletandcrushedrecycledconcreteitself.Eventhoughaggregatetypicallyaccountsfor70%to80%oftheconcretevolume,itiscommonlythoughtofasinertfillerhavinglittleeffectonthefinishedconcrete'sproperties.However,researchhasshownthataggregateplaysasubstantialroleindeterminingworkability,strength,dimensionalstability,anddurabilityoftheconcrete.Also,aggregatescanhaveasignificanteffectonthecostoftheconcretemixture.Certainaggregateparametersareknowntobeimportantforengineered-useconcrete,includinghardness,strengthanddurability.Theaggregatemustbe"clean,"withoutabsorbedchemicals,claycoatings,orotherfinematerialsinconcentrationsthatcouldalterthehydrationandbondofthecementpaste.

Itisimportanttonotethedifferencesbetweenaggregateandcementbecausesomematerialsusebothasacementitiousmaterialandasaggregate(suchascertainblast-furnaceslags).Aggregatecomposedofrecycledconcretegenerallyhasalowerspecificgravityandahigherabsorptionratethanconventionalgravelaggregate.Newconcretemadewithrecycledconcreteaggregatetypicallyhasgoodworkability,durabilityandresistancetosaturatedfreeze-thawaction.Thecompressivestrengthvarieswiththecompressivestrengthoftheoriginalconcreteandthewater-to-cementratioofthenewconcrete.Ithasbeenfoundthatconcretemadewithrecycledconcreteaggregatehasatleasttwo-thirdsthecompressivestrengthandmodulusofelasticityofnaturalaggregateconcrete.Fieldtestinghasshownthatcrushedandscreenedwasteglassmaybeusedasasandsubstituteinconcrete.Nearlyallwasteglasscanbeusedinconcreteapplications,includingglassthatisunsuitableforusessuchasglassbottlerecycling.Someofthespecificglasswastematerialsthathavefounduseasfineaggregateare"non-recyclable"clearwindowglass,andfluorescentbulbswithverysmallamountsofcontaminants.Possibleapplicationsforsuchwaste-glassconcretearebikepaths,footpaths,gutters,andsimilarnon-structuralwork.

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Thecurrentlackofwidespread,reliabledataonaggregatesubstitutescanhinderitsuse.Todesignconsistent,durablerecycled-aggregateconcrete,moretestingisrequiredtoaccountforvariationsintheaggregate'sproperties.Also,recycledaggregategenerallyhasahigherabsorptionrateandalowerspecificgravitythanconventionalaggregate.Researchhasrevealedthattheseven-dayand28-daycompressivestrengthsofrecycled-aggregateconcretearegenerallylowerthanvaluesforconventionalconcrete.Moreover,recycledaggregatesmaybecontaminatedwithresidualquantitiesofsulfatefromcontactwithsulfate-richsoilandchlorideionsfrommarineexposure.Glassaggregateinconcretecanbeproblematicduetothealkali-silicareactionbetweenthecementpasteandtheglassaggregatewhich,overtime,canleadtoweakenedconcreteanddecreasedlong-termdurability.Researchhasbeendoneontypesofglassandotheradditivestostopordecreasethealkali-silicareactionand,thereby,maintainfinishedconcretestrength.However,furtherresearchisstillneededbeforeglassculletcanbeusedinstructuralconcreteapplications.

Innovations:FibrousConcreteReinforcement

Reinforcingconcretetokeepitfromcrackingisnothingnew.Eventheearliestcivilizationsusednaturalfiberstoinhibitcrackinginmasonrystructures.Today,synthetic-fiberreinforcementisavailabletoreinforcenon-structuralconcreteapplicationswithsuperiorresults.Currently,themostwidelyusedformofreinforcementiswelded-wirefabric(WWF),ameshofsteelwiresthatisplacedinconcrete.However,synthetic-fiberreinforcementavoidstheincreasedlaborcostsanddifficultyinplacementthatareassociatedwithWWF.

Synthetic-fiberreinforcementpreventscracksinconcrete,unlikeWWF,whichcontrolscrackwidth.CracksactuallyneedtooccurbeforetheWWFgoestowork.Small-diametersyntheticfibers,suchasnylon,glass,steelandpolypropylene,arenowbeingaddedtoconcretetoreduceshrinkage-crackingbymorethan80%,accordingtoindependentlabtests.Reducingcracksimprovesconcreteimpermeability,increasesitstoughnessandlong-termweatherability,andcanreducecallbacksinconcreteslabfloors,decks,driveways,andwalkways.Accordingtofibermanufacturers,theplacement,curingandfinishcharacteristicsoftheconcretearenotaffectedbytheadditionoffibrousreinforcement.

Whenaddedathighercontentbyvolume,larger-diametersyntheticfibers,suchassteelandpolyolefin(addedat0.5%to1.5%,respectively),alsoenhancehardenedflexuralstrength,butatanincreasedcost.Fibrousreinforcementisusedprimarilytoreducecrackinginnon-structuralconcreteapplications.However,steelfibersrustandcancausesurfacediscoloration.

Innovations:AutoclavedAeratedConcrete

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BuildersintheU.S.canuseaninnovativeconcretematerialthatScandinavianshaveusedfordecades.Autoclavedaeratedconcrete(AAC)isaprecaststructuralproductmadewithnaturalrawmaterials.In1914,theSwedesinventedamixtureofcement,lime,waterandsandthatexpandsbyaddingaluminumpowder.Thematerialwasfurtherdevelopedtowhatweknowtodayasautoclavedaeratedconcrete,whichisalsocalledautoclavedcellularconcrete.Itisaneconomical,sustainable,solidblockthatprovidesthermalandacousticinsulation,aswellasfireandtermiteresistance.AACisavailableinavarietyofforms,rangingfromwallandroofpanelstoblocksandlintels.AlthoughithasbeenapopularbuildingmaterialinEuropeforover50years,AAChasonlybeenintroducedtotheU.S.inthepasttwodecades.

TomanufactureAAC,Portlandcementismixedwithlime,silicasandorrecycledflyash(abyproductfromcoal-burningpowerplants),water,andaluminumpowderorpaste,andthenpouredintoamold.Thereactionbetweenaluminumandconcretecausesmicroscopichydrogenbubblestoform,expandingtheconcretetoaboutfivetimesitsoriginalvolume.Afterthehydrogenevaporates,thenowhighlyaeratedconcreteiscuttosizeandformedbysteam-curinginapressurizedchamber--anautoclave.Theresultisanon-organic,non-toxic,airtightmaterialthatcanbeusedforwall,floorandroofpanels,blocksandlintels,andwhich,accordingtothemanufacturers,generatesnopollutantsorhazardouswasteduringthemanufacturingprocess.AACunitsareavailableinnumerousshapesandsizes.Panelsare24incheswide,between8to12inchesthick,andupto20feetlong.Blockscomeinlengthsof24inches,32inchesand48inches,between4to16inchesthick,and8incheshigh.AACfeaturesincludestructuralcapacity,thermal,fireandacousticalresistanceproperties.WithanR-valueofapproximately1.25perinch,dependingondensity,AACsignificantly

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out-performsconventionalconcreteblockandpouredconcrete.ConsistencyinqualityandcolormaybedifficulttoobtaininAACmadewithflyash.Unfinishedexteriorwallsshouldbecoveredwithanexteriorcladding,orpargedwithmortar,whenexposedtophysicaldamage,dirtandwaterbecauseatmosphericdebriscancollectintheopencells.Ifinstalledinhigh-humidityenvironments,interiorfinisheswithlow-vaporpermeabilityandexteriorfinisheswithahigh-permeabilityarerecommended.BecauseofthethermalmassofAACanditsabilitytostoreandreleaseenergyovertime,AACmaybebeneficialinclimateswhereoutdoortemperaturefluctuatesovera24-hourperiodfromabovetobelowtheindoortemperatureconditionedair-setpoint.

CrackinginConcreteCrackingAssociatedwithDryingShrinkageinConcreteBlockFoundationWalls

Theshrinkageofconcreteblockwallsduringthedryingprocesswilloftenresultinpatternsofcrackingsimilartothatcausedbydifferentialsettlement:taperingcracksthatwidenastheymove,resultinginadiagonalupwardpattern.Thesecracksusuallyformduringthebuilding’sfirstyearand,inexistingbuildings,willappearas“old”cracksandexhibitnofurthermovement.Althoughsuchcracksareoftenmistakenforsettlementcracks,shrinkagecracksusuallyoccurinthemiddlethirdofthewall,andthefooterbeneaththemremainsintact.Shrinkagecrackingisrarelyseriousand,inanolderbuilding,mayhavebeenpreviouslyrepaired.Ifthewallisunsound,itsstructuralintegritycansometimesberestoredbypressure-injectingconcreteepoxygroutintothecracks,orbyaddingpilasters.

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Howback-fillingcanaffectfoundationwalls:

Howhorizontalcracksrelatetofoundationwallmovement:

SweepingorHorizontalCrackingoftheFoundationWalls

Thesweepingorhorizontalcrackingofbrickandconcreteblockfoundationwallsmaybecausedbyimproperback-filling,vibration(fromthemovementofheavyequipmentandvehiclesclosetothewall),andbytheswellingorfreezingandheavingofwater-saturatedsoiladjacenttothewall.Liketheshrinkageassociatedwithdrying,sweepingorhorizontalcrackingmayhaveoccurredduringtheoriginalconstructionandwascompensatedforatthattime.Suchdistress,however,ispotentiallyserious,asitindicatesthattheverticalsupportingmember--thefoundationwall--thatiscarryingaportionofthestructureaboveisbentorbroken.Itmaybepossibletopushthewallbackintoplacebycareful

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jacking,andthenreinforcingitwiththeadditionofinteriorbuttresses,orbypressure-injectingconcreteepoxygroutintothewall.Ifoutsidegroundconditionsallow,thewallcanberelievedofsomelateralpressurebyloweringthegroundlevelaroundthebuilding.Whenexpansivesoilissuspectedasthecauseofthecracking,examinetheexteriorforsourcesofwater,suchasbrokenleadersorpoorsurfacedrainage.Frost-heavingmaybetheculpritifthedamageisabovelocalfrostdepth,orifitoccurredduringanespeciallycoldperiod.

Settlement

Allstone,brick,concreteandconcreteblockfoundationsshouldbeinspectedforproblemsassociatedwithdifferentialsettlement.Althoughserioussettlementproblemsarerelativelyuncommon,unevenordifferentialsettlementcanbeamajorstructuralprobleminsmallresidentialbuildings.Manysignsofmasonrydistressareincorrectlydiagnosedassettlement-relatedwhen,infact,theyareduetomoistureandthermalmovements.

Indicationsofdifferentialsettlementareverticaldistortionandcrackingofmasonrywalls,warpedinteriorandexterioropenings,slopedfloors,andstickingdoorsandwindows.Settlementmostoftenoccursearlyinthelifeofabuilding,andwhenthereisadramaticchangeinundergroundconditions.Often,suchsettlementisassociatedwithimproperfoundationdesign,particularlyinadequatefootersandfoundationwalls.

Othercausesofsettlementinclude:

•soilconsolidationunderthefootings;•soilshrinkageduetothelossofmoisturetonearbytreesandlargeplants;•soilswellingduetoinadequateand/orblockedsurfaceorhousedrainage;•soilheavingduetofrostandexcessiverootgrowth;•gradualdownwarddriftofclaysoilsonslopes;•changesinwatertablelevel;•soilerosionaroundfootersfrompoorsurfacedrainage,faultydrains,leakingwatermains,andotherundergroundwatermovements.Occasionally,undergroundwatermayscourawayearthalongonlyonesideofafooter,causingitsrotationandthesubsequentbucklingordisplacementofthefoundationwallabove;and•soilcompactionandmovementduetovibrationfromheavyequipment,vehiculartraffic,blasting,and/orfromgroundtremors(earthquakes).Gradualdifferentialsettlementoveralongperiodoftimemayproducenomasonrycrackingatall,particularlyinwallswitholderandsofterbricksandhighlimemortars;instead,thewallwillelasticallydeform.

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Morerapidsettlement,however,producescracksthattaper,startinglargeatoneendandthendiminishingtoahairlinecrackattheotherend,dependingonthedirectionandlocationofsettlementbelowthewall.Crackingismostlikelytooccuratcornersandadjacenttoopenings,andusuallyfollowsaroughdiagonalpathalongmortarjoints,althoughindividualmasonryunitsmaybesplit.Settlementcracks(asopposedtothesimilar-appearingshrinkagecracksthatareespeciallyprevalentinconcreteblock)mayextendthroughcontiguousbuildingelements,suchasfloorslabs,masonrywallsabovethefoundation,andinteriorplasterwork.Taperingcracks,orcracksthatarenearlyverticalandwhoseedgesdonotlineup,mayoccuratthejointsofprojectingbaywindows,porches,andadditions.Thesecracksindicatedifferentialsettlementduetoinadequatefoundationsorpiersundertheprojectingelement.

Thispierhasbeenoverstressedbymovementoftheporchandcolumn.Theentireassemblyshouldberebuilt.

Often,settlementslowsashorttimeafterconstruction,andapointofequilibriumisreachedwhenmovementnolongeroccurs.Minorsettlementcrackingisstructurallyharmfulonlyiflong-termmoistureleakagethroughthecracksadverselyaffectsthebuilding'selements.Largedifferentialsettlements,particularlybetweenfoundationwallsandinteriorcolumnsorpiers,aremoreseriousbecausetheywillcausemovementincontiguousstructuralelements,suchasbeams,joists,floorsandroofs.Theseelementsmustbeevaluatedforlossofbearingand,occasionally,fractures.Shouldstrengtheningofthefoundationberequired,itcanbeaccomplishedbytheadditionofnewstructuralelementssuchaspilasters,orbypressure-injectingconcrete.Itispossiblethattheproblemcanonlyberectifiedbyunder-pinning.Olderbuildingswithseveresettlementproblemsmaybeverycostlytorepair.Insuchcases,recommendtheadviceofastructuralorsoilengineer.

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Theeffectsofsoilpressureonfoundationwalls:

ProblemsAssociatedwithMasonryPiers

Masonrypiersareoftenusedtosupportinternalloadsonsmallresidentialbuildings,andtosupportprojectingbuildingelements,suchasbaywindows,porches,andadditions.Insomecases,theysupporttheentirestructure.Piersoftensettledifferentiallyandoveralongperiodoftime,particularlywhentheyareexposedtotheweather.Sometimes,theytendtodeteriorate.Commonproblemsinclude:

• settlementorrotationofthepierfooting,whichcausesaloweringortiltingofthepier,andsubsequentlossofbearingcapacity.Woodframestructuresadjusttothisconditionbyflexingandredistributingtheirloads,orbysagging.Masonrywallslocatedoversettledpierswillcrack.

• frost-heavingofthefootingorpier,aconditioncausedbythelackofanadequatefootingoroneofinsufficientdepth.Thiswillcausethepiertoriseortiltandtrigger

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structuralmovementaboveit,similartothatcausedbysettlementorrotationofthefooting.Suchaconditionismostcommonunderporches.

• physicaldeteriorationofthepierduetoexposure,poorconstruction,orover-stressing.Above-groundpiersexposedtotheweatheraresubjecttofreeze-thawcyclesandsubsequentphysicaldamage.Piersinmanyolderresidentialstructuresareoftenofmadeofpoorlyconstructedmasonrythatdeterioratesovertheyears.Asignofover-stressedpiersisverticalcrackingandbulging.

• lossofbearingofbeams,joists,orfloorsduetotheaboveconditions,orduetomovementofthestructureitself.

Piersshouldbeexaminedforsignsofsettlementandtheiradequacyinacceptingbearingloads.Inspectorsshouldnotetheirconditionandensurethattheyareplumb.Checktheirwidth-to-heightratio,whichshouldnotexceed1:10.Piersthataredeficientshouldberepairedorreplaced.Whenappearanceisnotafactor(asisoftenthecase),pierscanbesupplementedbytheadditionofadjacentsupports.

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BrickVeneerWallsProblemsAssociatedWithBrickVeneerWalls

Brickveneerwallsaresubjecttotheforcesofdifferentialsettlement,moistureandthermal-relatedcracking,andtheeffectsoffreezingandcorrosion.Commonproblemsparticulartobrickveneerwallsare:

• crackscausedbywoodframeshrinkage,whicharemostlikelytobefoundaroundfixedopeningswheretheindependentmovementoftheveneerwallisrestrained.Thesecracksarealsoformedearlyinthelifeofthebuildingandcanberepairedbypointing;

• bulging,whichiscausedbyinadequateordeterioratedtiesbetweenthebrickandthewalltowhichit’sheld;and

• verticalcrackingatcorners,and/orhorizontalcrackingneartheground,whichiscausedbythermalmovementofthewall.Thiscrackingissimilartothatinsolidmasonryandmasonrycavitywalls,butpossiblymorepronouncedinwell-insulatedbuildingsbecauseofthereductioninthemoderatingeffectfrominteriortemperatures.Thermalcracksarecyclicalandshouldbefilledwithaflexiblesealant.Incasesofseverecracking,expansionjointsmayhavetobeinstalled.

Adeterioratedparapetwallthatbadlyneedsrepointing.Fortunately,thewallhasnotyetexhibitedseriousmovement,butitwill,ifleftindisrepair.

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Quiz2Retardingadmixturesslowdownthehydrationofcement,whichlengthensits______.

• settime• lifespan• amount

Acceleratingadmixtures________thesettimeofconcrete.

• shorten• lengthen• eliminate

Super-plasticizersare____________.

• "high-rangewaterreducers"• "free-rangewaterinhibitors"• "low-rangewaterreducers"

Water-reducingadmixturesaremostlyusedfor____________.

• hot-weatherconcreteplacing• cold-weatherconcreteplacing• high-altitudeconcreteplacing

Air-entrainingadmixturesentrain__________intheconcrete.

• smallairbubbles• smallwaterdroplets• dryconcretedust

T/F:Admixturescanusuallycompensateforpoorworkmanshipandlow-qualitymaterials.

• False• True

_________cracksareoftenmistakenforsettlementcracks.

• Shrinkage• Seismic• Frost-heave

Sweepingcracksinthefoundationare______________.

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• potentiallyserious• commonandnon-serious• primarilycosmeticinnature

Rapidsettlementproduces________cracks.

• tapering• widening• serious

T/F:Frozensoilexertsagreaterforceagainstthefoundationthanwetsoil.

• True• False

T/F:Inspectorsshouldnotetheconditionofmasonrypiersandensurethattheyareplumb.

• True• False

Somecausesoffoundationsettlementinclude:_____________.

• allofthese• soilswelling• soilshrinkage• soilerosion• soilcompaction

MasonryandConcreteAdhesives

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Mortarhastraditionallyprovidedthebondingagentformasonryunits.Theprincipletypes,M,N,SandO,useacombinationofcements,lime,sandandwatertoholdbuildingblockstogetherandprovideasealfromtheelements.However,asnewadhesivesaredeveloped,manufacturershaveexperimentedwiththeirusetoimprovebondstrengthandreducelaborcosts.Masonryadhesivesarepre-mixedandavailableinseveralpackagingformats,fromcaulktubesandsqueezebottlestopressurizedbulkcontainers.Severalbeadsofthemixcanbeappliedatthesametimewhenanapplicationwandisused.

Innovations:ConcreteWaterproofingSystems

Anyonewhohasexperienceddamagefromwaterseepageknowsthatrepairisacostlyandtime-consumingprocess.Onewaytohelpreducewaterseepageisbyusingcrystallineconcretewaterproofing.Thismethodusesacatalyticreactiontosealthepores,capillariesandshrinkagecracksthatoccurnaturallyinconcrete.Crystallinewaterproofingpenetratesintotheconcrete.Longavailableforindustrialapplications,crystallinewaterproofingisnowreadyforuseinresidentialapplications.ItconsistsofadrypowdercompoundofPortlandcement,veryfinetreatedsilicasand,andproprietarychemicals.Combiningtheproductwithwaterandapplyingittothesurfaceofconcreteresultsinacatalyticreactionthatformsnon-solublecrystallinefiberswithintheporesandcapillarytractsofconcrete.Thissealstheconcreteagainstmoisturepenetration.

Crystallinewaterproofingreplacestraditionalsolvent-basedwaterproofingonfoundationwalls.However,exteriorparging,bituminouswaterproofing,oradrainablelayermayberequiredbythebuildingcode.

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Waterpenetrationthroughbasementandcrawlspacefoundationwallsisusuallycausedbycondensationand/orfromanexteriorwatersourceduetoinadequategrading,rainwatercollection,and/orpoorfootingdrains.Thesourceofcondensationorexteriorwaterintrusionmustbecorrectedpriortotheapplicationofcrystallineconcretewaterproofing.

Water-ResistantPolyethyleneSub-FloorSystem

Polyethyleneflooringsystemsthatarespeciallydesignedforuseoverconcretefloorscanalleviatemoistureproblemsassociatedwithplacingwoodsub-flooringindirectcontactwithconcreteslabs.Thesystemsaremadeofamoldedpolyethylenebase.Thebasepreventsthemigrationofmoisture,whileitsundulating,raisedpatterncreatesanairspacebetweensub-floorandconcrete.Onetypeofpatternresemblesplasticcleats,whileanotheriszig-zag.

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FoundationDrainagePanels

Thefoundationisavulnerableplaceforwaterintrusion.Improperdrainagearoundthefoundationisamajorcauseofleakingfoundations.Whenadrainagesystemisusedinresidentialconstruction,itisusuallyacombinationofalayerofgravelfordrainagewithafoundationdrain,usuallyeitherdraintileorperforatedPVCpipe.Monthslater,asdrainageoccurs,smallsoilparticlescanfillthedrainagepath,resultinginreduceddrainageofgroundwater.Waterpressurethenbuildsupandeventuallycausesleakagethroughthefoundationwall.Engineered,prefabricatedfoundationdrainagepanelsaredesignedtofacilitatethemovementofgroundwater,whichreducesthestressofthewaterpressureonthefoundation'swaterproofing.Thedrainagepanelsprovideanunobstructedpathfromthesurfacegradetothefooting,allowingthefootingdraintocollectandmovewaterawayfromaroundthefoundation.Someofthesesystemsalsoprovidethermalresistanceandcanreduceinteriorcondensation.Foundationdrainagepanelsystemscombinewithwaterproofingmembranestoprovideprotectionfromgroundwaterinareaswherethereisahighwatertableand/orhydrostaticpressure.Thestandardgraveldrainagecourseandfoundationdrainswithdamp-proofingonthefoundationareapplicableinareaswithoccasionalornogroundwater.

Thetypicalfoundationdrainagesystemconsistsofawaterproofingmembraneatthefoundationwithapre-formedpath,suchasagridsystemorasolidporousboard,andafiltertokeepthedrainpathclearofsmallparticlebuildup.Thefilterisusuallyacourseofspecially-gradedaggregates,rangingfromcrushedstoneandgraveltocoarse,angularsand.Geotechnicalfabrics,commonlycalled"filterfabrics,"arenowfrequentlyusedtoallowtheflowofwaterwhilepreventingsmallparticlesfrompassingthrough.Thesefabricsuselessspace,aremorereliable,andarerelativelyeasytoinstall.Thedrainagepathcanbedesignedusingseveraldifferentmethods:

• asoliddrainageboardwithaporousstructure,allowingmoistureandwatertodrainverticallydowntothefoundationdrain.Theseboard-typesystemsprovideprotectionofthewaterproofmembraneandthermalinsulation;

• anairspacecreatedbyadimpledplasticgrid,or"geogrid."Condensationcanalsobecollectedinthisairspace;

• atraditionalgravelcourse,withfilterfabrictotheoutside,andaprotectionboardoverthefoundationwaterproofing.Washedpea-gravelandscreenedcrushedstoneworkwellforthisdrainagecourse;and

• panelswithanairspacetoquicklymovethewatertothedrains,reducinghydrostaticpressureagainstthefoundation.

Mostofthesesystemsalsoprovideprotectiontothedamp-prooforwaterproofmembrane.Dimpledpolyethylenesheetscanbeusedintwoways:

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• withthedimplestowardthefoundationwall.Thisprovidesanairspaceforcondensation,usingthebacksideasanimperviousbarrier.Whenproperlysealed,thesystemresistsgroundwaterpercolatingthroughtothefaceofthefoundation,therebyprotectingitfromthemoisture.

• someproductshaveafilterfabricadheredtothedimple-sideofthepanel.Inthiscase,theflatsideofthepanelisplacedtowardthefoundation.Thedrainagepathiscreatedbythedimples,andprotectedbythefilterfabric.

Anothermethodforprovidingapathwiththefilterfabricistheuseofa"geogrid."Ageogridisatwisted-wireplasticmesh,oftenshapedintoadiamond-lathpattern,facedwithfilterfabric.Thesearenormallyratherthin,flatmembranesofferingeffectivedrainagecharacteristicsinaminimalspace.Enkadrain™employsafused,entangledpolymerfilamentgeomatrix,orplasticwiremesh,facedwithfilterfabrictoprovidethedrainagelayer.TheAmericanWickDrainCorporationmakesasheet-drainsystemconnectedtoastripdrainatthebottomofthefoundationwall.Thestripdraincanbeconnectedtopipingtoleadthewaterawayfromthefoundation.Form-a-DrainÒ,madebytheCertainteedCorporation,isarectangulardrainageconduitthatalsoactsasafootingform,savingseveralinstallationsteps.Foamplasticinsulatedpanelsmaybeusedoutsidefoundationwallstomovewatertodraintileorpipeatthebottomofthewall.Asmentionedpreviously,thesepanelsalsoprovidethermalinsulation.Panelsmayormaynotbefacedwithageotextilemembrane.Geotech™,forexample,isanun-facedboardofexpandedpolystyrene.Itallowswatertomovebetweenthebeadstructureofthematerial,andthepolystyreneoffersinsulatingvalue.Otherfoamfoundationpanelsaremadefromextrudedpolystyrene,groovedonthesoil-sideandcoveredwithfilterfabric.Thefilterfabricallowsthewatertoenterthegrooveswhich,inturn,transfersittothedraintile.Thepolystyreneinsulationhasalowpermeabilityrating,andprovidesinsulativevalue.Somedrainagepanelsarecomposedofrock(mineral),wool,andfiberglassmaterialorientedtoprovideverticaldrainagetothefoundationdrain.Nofilterfabricisnecessarywiththesematerials.

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FoundationFloodVents

TobeeligibleforfloodinsurancethroughFEMA'sNationalFloodInsuranceProgram(NFIP),foundationsmustbeconstructedwithcertainflooddamage-mitigationfeatures.Incoastalareasandriverinezoneswherehigh-velocityfloodwaterscanoccur,homesmustbeelevatedonopen-pilefoundations,andenclosuresbelowthelivingspacemustbelocatedatanelevationhigherthanthe100-yearbasefloodelevationandmustbedesignedtobreakawayinastormsurge.Homesbuiltinfloodplainswherefloodwatervelocitylevelsarelowerthancoastlinesandriverinezones(lessthan5feetpersecond),andonperimeter-typefoundations,shouldbedesignedsothattheexteriorwallsofthefoundationautomaticallyequalizehydrostaticfloodforcesbyallowingforthefreeflowoffloodwater.Thisminimizesstructuralflooddamagebyreducingthehorizontalhydrostaticforcethatunbalancedwaterlevelsimposeonfoundationwalls.FoundationdesignsmeetingNFIPrequirementsmustincludeprescribedopeningsoranengineer'scertificationthatthefollowingminimumcriteriahavebeenmet:

• Aminimumoftwoopenings(ondifferentfoundationwallelevations)havingatotalnetareaofnotlessthan1squareinchforeverysquarefootofenclosedareasubjecttofloodingshallbeprovided.

• Thebottomofallopeningsshallbenohigherthan1footabovegrade.• Openingsmaybeequippedwithscreens,louvers,valves,orothercoveringsor

devices,providedthattheypermittheautomaticentryandexitoffloodwaters.

AnyopeningsthatallowforthefreeflowoffloodwaterintooroutofafoundationwillmeetNFIPrequirements,subjecttominimumsizeandlocationcriteria.Evenvoidsinthecontinuityofablockfoundation(or"blocksturnedsideways,"asoneMarylandDepartmentoftheEnvironmenttechnicalnotereferstoit)willsuffice.Dependingontheirmethodofoperation,conventionalcrawlspaceventilationgrillsmayalsoservetoequalizewateraroundthefoundationduringaflood.However,someairventsthatarethermostaticallycontrolledmaynotdisengageincoldweathertoallowwaterentry.Ifcrawlspaceventswillalsobeusedasfloodwatervents,thenumberandlocationofventstobeusedshouldbespecified,basedonthefloodwaterventcriteria.Severalmanufacturershavedevelopedunitized,shutteredproductsthatmeettheminimumfloodventingrequirementsofNFIP.SmartVent,Inc.marketsseveraltypesofvents,includingtheSmartVENT®,whichautomaticallyopensandclosesasfloodwatersriseandfall.Italsofeaturestemperature-controlledlouverswhichopeninwarmweathertoprovide50inchesofnet-freeventilationarea,andthencloseincoldweather.EachSmartVENT®,sized8x16inches,iscertifiedtoprotect200squarefeetoffoundationarea.Anothermodel,FloodVENT™,isusedwhenfloodprotection,notventilation,isneeded.

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Thismodelhasanon-ventedinsulateddoorthatminimizesheatloss,airleakage,andpestintrusionwhenthedoorisclosed,butswingsopenduringaflood.Anothermanufacturer,Floodex™,hasobtainedpre-certificationofitsfloodwatervent.

SteelFoundationSystems

TheFastTrackFoundationSystem®isaseriesofstructuralcorrugatedsteelwallpanelspositionedalonganexistingin-placestructure,thencastintoplace,creatingafoundationwall.Thefoundationpanelscanbeusedfornewconstruction,foundationretrofits,andmodularandmanufacturedhomes.Thefoundationsystemcanalsobeusedinlow-costtornadoshelterapplications.FastTrackSystems®receivedrecognitioninthe2002InnovativeHousingTechnologyCompetition,whichisco-sponsoredbyPopularSciencemagazineandtheNAHBResearchCenter.Thepanelmaterialiscommerciallyavailablecorrugatedsteel,18-gauge,galvanizedG-90"B-deck"(1.5-inchthick).Thebottompaneledgesarecastintoaconcretefooting,providinganchorageandbearing.Withverticalflutes,panelsserveasabearingfoundationwall.Panelsarejoinedtogetherwithacaulkedjointalongthecontiguous-edge,andthentheyaretreatedwithaprotectivecoating.

Frost-ProtectedShallowFoundations(FPSFs)

Frost-protectedshallowfoundations(FPSFs)provideprotectionagainstfrostdamagewithouttheneedforexcavatingbelowthefrostline.AnFPSFhasinsulationplacedstrategicallyaroundtheoutsidewallstodirectheatlossfromthebuildingtowardthe

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foundation,andalsotousetheearth'snaturalgeothermalenergy.Traditionally,foundationsareprotectedfromfrost-heavingdamagebyplacingthefootingbelowthefrostline.BecauseFPSFsareprotectedfromfreezingbythermalinsulation,thebottomsoffootingscanbejust12to16inchesbelowgrade.Thisreducesexcavationcosts,makingFPSFsaneconomicalalternativeforprotectingfoundationsagainstfrostdamage.Insulatedfootingshavebeeninusesinceasearlyasthe1930sbyFrankLloydWrightintheChicagoarea.Therearenowmorethan1millionhomesinNorway,SwedenandFinlandwithinsulatedshallowfootings,recognizedbytheirbuildingcodesasstandardpractice.Itisestimatedthattherearemorethan5,000buildingsintheUnitedStatesthathavesuccessfullyusedfrost-protectedshallowfoundations.FPSFsaresimilartoconventionalfoundationsexceptininsulationplacementandfootingdepth.ThebottomsofFPSFfootingsareplacedabout12to16inchesbelowgrade.FPSFshaveverticalinsulationplacedattheoutsideedgeofthefoundation,extendingfromabovegradetothebottomofthefooting.

Whenrequiredincolderclimates,"wing"insulationextendsoutwardhorizontallyfromthefooting.Thecoldertheclimate,thefurtherthewinginsulationisextended.Winginsulationisunnecessaryinmoderateclimates.TheinsulationusedinFPSFsiscommonlyrigidexpandedorextrudedpolystyrenefoamsuitableforbelow-gradeapplication,anditmustbeincompliancewithASTMC578Standards.AnFPSFcanbeusedforbothheatedandunheatedportionsofabuilding.

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WoodFoundations

Preservative-treatedlumberispressure-infusedwithchemicalstoresistinfestationanddecay,andtheprocessissoeffectivethatmanufacturersarenowrecommendingtreatedplywoodandlumberasanalternatematerialforcrawlspace,basementandstem-wallfoundations.Usingawoodfoundationsystemeliminatestheneedtocastandcureconcretefootings(althoughaslabfloormaybeincluded),andallowsconstructioninanyweatherbythesamecrewthatcompletesotherwoodframing.Woodfoundationsalsoresistcracking,andareeasytoinsulateandfinishforadditionalinteriorlivingareas.Morethan300,000U.S.homeshavebeenconstructedwithwoodfoundationsystems.Woodfoundationsystemswerefirstdevelopedinthe1960s,afterthedevelopmentofpreservative-treatedlumberandplywoodallowedwoodmaterialstobeusedinapplicationsforwhichitpreviouslywouldhavebeensubjecttodecay.Manufacturersthatproducepreservative-treatedlumberandrelatedapplicationshavedevelopedproceduresandguidelinesforconstructingwoodfoundations,whileothercompaniesspecializeincustom-designedandpanelizedsystems.Becausewoodfoundationsaresignificantlylighterthanconcreteandblockwalls,theymaybeplacedongravelbeds,eliminatingtheneedtocastandcureaconcretefooting.

Aconcreteslabmayformthefloorwithinthefoundation,butmostmanufacturerspromotetheuseofatreatedwoodfloorsystem.Thiseliminatesconcreteworkfromtheschedulealtogether,allowingconstructiontoproceedinanyweather,withworkcompletedbythesamecrewthatdoestherestofthewoodframing.

Typically,wallsareframedwith2x8treatedstudson16-inchcenters,orasspecifiedbythedesigners.Theexteriorfoundationsurfacesarecladwith1/2-inchor5/8-inchtreatedplywood,withpolyethylenefilmappliedbeforeback-filling.

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Forbasementsfinishedaslivingspace,thecavitiesofthewoodfoundationframingareeasilyinsulatedwithconventionalbattsorblowncellulose.Plumbing,wiringanddrywallareinstalledasforanyframedwall.Finishingconcreteandblockwallsmightrequirechaseconstruction,specialcuttingequipment,furringstrips,and/ormasonryadhesive.Manufacturersstatethatwoodfoundationsarealsomorethermallyefficientandelasticand,therefore,lesssubjecttocrackingandmoisturepenetration.Permanentwoodfoundationsmustbepreservative-treatedinaccordancewiththeAmericanWood-Preservers'Association(AWPA)StandardC22,titled"LumberandPlywoodforPermanentWoodFoundations:PreservativeTreatmentbyPressureProcesses."

ICFWalls:WoodFiberCompositeForms

Concretewallscanbeconstructedofcement-bondedrecycledwood-chipinsulatedconcreteforms(ICFs)thatholdconcreteinplaceduringcuring,andremaininplacetoprovidethermalandnoiseinsulation.Theblocksarelightweight,andareavailablewithmineral-fiberinsulationtoprovideanenergy-efficient,fire-andtermite-resistant,durablestructuralwallsystem.Thesystemisinherentlymoisture-regulating,capableofabsorbinghighlevelsofmoistureintheairwithoutdamage.Thewallform,however,doesnotsupportorpromotefungalormoldgrowth.Thematerialiscapableofbeinginstalledbothaboveandbelowgrade,andisavailableinvariouswidthsandinsulationthicknesses.Cement/woodfiberblocksaresimilartothenewerICFsystemscomprisedoffoaminsulationwithmetalorplasticjoinerties.Cement/woodfiberblocksareintendedtobedry-stacked,andaredesignedwithhorizontalandverticalcellsthatarefilledwithconcretetoformthestructuralportionofthewall.Verticalandhorizontalinterlockingchannelssimplifyalignment.Thewoodfiberusedinthemanufactureoftheblockmaybepartiallyorfullycomprisedofpost-industrialsoftwood,whichisthenmineralizedwithcement.Thebasicmaterial'sheat-resistanceisapproximately1.75perinchthickness.Theproduct'sR-valuerangesfromaboutR-8foran8-inchblockwithnoadditionalinsulation,toR-20fora12-inchblockwitha3-inchmineralwoolinsert.NobridgingoccurssincethesolidportionsofthematerialattheribshaveaninsulativevalueofaboutR-14.

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Thehygroscopicpropertiesofthematerialallowittoreadilytakeupexcessmoistureintheairandstoreitwithoutitbeingabsorbed,andwithoutdamagetothematerial.Thisattributehelpstobalancechangesintherelativehumidityoftheindoorenvironment.Ontheexterior,thematerialcanactasadrainageplaneifsubjectedtoliquidwater—adistinctpossibilityinabasement.Anairbarriermayberequiredforsomefinishes.Thethermal-massbenefitsoftheconcreteareenhancedwithcement/woodfiberblocks,sinceatleasttwo-thirdsoftheinsulationisontheexteriorofthemass.Thisproximityofthemasstotheindoorenvironmentservestostabilizetheindoorairtemperature,andtotakeadvantageofdirectsolargainsinheatingperiods.

VaporBarriersCrawlspaceVaporBarriers

ThroughouttheUnitedStates,evenindesertareas,thereismoistureinthegroundfromgroundwaterbeingabsorbed.Eveninanapparentlydrycrawlspace,alargeamountofwaterisenteringthehome.Inadrycrawlspace,themoistureisdryingoutasfastasitisentering,whichcauseshighmoisturelevelsinthecrawlspaceandelsewhereinthehouse.Asolidvaporbarrierisrecommendedinallcrawlspaces,andshouldberequiredifmoistureproblemsexist.Thisvaporbarrier,ifproperlyinstalled,alsoreducestheinfiltrationofradongas.Ofcourse,ifthemoistureiscomingfromaboveground,avaporbarrierwillcollectandholdthemoisture.Therefore,anyabove-groundsourceofmoisturemustbefoundandeliminated.Thesourcemaybeasobviousassweatingpipes,ormaybemoredifficulttospot,suchascondensationonsurfaces.Thesolutioncanbeassimpleasapplyinginsulationtoexposedsectionsofthepiping,orcomplexenoughtorequirepowerexhaustfansandtheadditionofinsulationandvaporbarriers.Themorecommoncausesofmoistureproblemsinanewhomearemoisturetrappedwithinthestructureduringconstruction,andacontinuingsourceofexcessmoisturefromthebasement,crawlspaceorslab.Toresolvethispotentialproblem,6-milplasticsheetsshouldbelaidasvaporbarriersovertheentirecrawlspacefloor.Thesheetsshouldoverlapeachotherbyatleast6inches,andshouldbetapedinplace.Theplasticshouldextenduptheperimeterwallsbyabout6inches.Theplasticsheetsshouldbeattachedtotheinteriorwallsofthecrawlspacewithmasticorbattenstrips.Alloftheperimeterwallsshouldbeinsulated,andinsulationshouldbebetweenthejoistsatthetopofthewalls.Vents,whichmayneedtobeopenedinthelatespringandclosedinthefall,shouldnotbeblocked.Ifnotproperlymanaged,moistureoriginatinginthecrawlspacecancauseproblemswithwoodflooring,andcreatemanybiologicalthreatstohealthandproperty.Aproperlyplacedvaporbarriercanpreventorreduceproblemmoisturefromenteringthehome.Concretepaints,water-proofingsealersandcementcoatingsareatemporaryfix.Theycrackandpeel,andcannotstopgases,suchaswatervaporandradon.

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Dampbasementairspreadsmoldandradonthroughthehouse.Efflorescence(whitepowderstains)andmustyodorsaretelltalesignsofmoistureproblems.Basementremodelingtrapsinvisiblewatervapor,causingmoldandmildew.

Mostbasementsstartleakingwithin10to15years.Thebasementwallsandfloorsshouldbesealedandpreservedbeforetheydeteriorate.Thebasementfloorshouldbeconcretewhichhasbeenpouredonatleast6inchesofgravel.Thegraveldistributesgroundwatermovementundertheconcretefloor,reducingthepossibilityofthewaterpenetratingthefloor.Awaterproofmembrane,suchasplasticsheeting,shouldbelaidbeforetheconcreteispouredforadditionalprotectionagainstfloodingandinfiltrationofradonandothergases.Thebasementfloorshouldbegraduallybutuniformlyslopedinalldirectionstowardadrainoraseriesofdrains.Thesedrainswillpermitthebasementtodrainifitbecomesflooded.Waterandmoisturemarksonthefloorandwallsaresignsofineffectivewater-proofingormoistureproofing.Cellardoors,hatchwaysandbasementwindowsshouldbeweather-tightandrodent-proof.Ahatchwaycanbeinspectedbystandingatthelowerportionwiththedoorsclosed;ifdaylightcanbeseen,thedoorneedstobesealedorrepaired.

VaporBarriersforConcreteSlabHomes

Strip-flooringandrelatedproductsshouldbeprotectedfrommoisturemigrationbyaslab.Properon-gradeorabove-gradeconstructionrequiresthatavaporbarrierbeplacedbeneaththeslab.Moisturetestsshouldbedonetodeterminethesuitabilityoftheslabbeforeinstallingwoodproducts.Avaporbarrierequivalentto4-or6-milpolyethyleneshouldbeinstalledontopoftheslabtofurtherprotectthewoodproductsandtheresidentsofthehome.

PlasticDuctworkSystems

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Plasticductworksystemsarewell-suitedforundergroundapplicationsbecausetheyareresistanttorustandotherformsofcorrosion.Thesesystemsaremanufacturedwitheitherhigh-densitypolyethylene(HDPE)orpolyvinylchloride(PVC).Wheninstalledproperly,theyarewatertightandairtight,andcanwithstandtemperaturesupto150°F.Plasticductworkisavailableindiametersof4to24inches,withavarietyoffittings,includingTs,Ys,elbows,45-degreeelbows,registerboxes,saddleboots,saddleconnections,reducers,couplings,endcaps,andstartingcollars.Plasticplenumboxesarealsoavailableforundergroundinstallation.Whileitispreferabletoinstallductworkinconditionedspacestomaximizeenergy-efficiency,itisnotalwayspossible.InsomeareasoftheUnitedStates,placingductsundergroundmaybethenextbeststrategy,particularlyiftheslabedgeisinsulated.Inhotclimates,forexample,itismoreenergy-efficientforthecoolingductstobeundertheslabthanexposedinahotattic.Inareaswheregroundmoistureandwaterintrusionmaybeanissue,however,extracaremustbetakenwheninstallingtheundergroundductworktoprotectitfromexcesswater.HDPE

Theseundergroundairductsandfittingsystemswerefirstintroducedintothemarketin2003forusewithforced-airheatingandcoolingsystems.Theductsconsistofahigh-densitypolyethylene(HDPE)linercoveredwithalayerofair-entrainedpolyethylene.TheHDPEpipeshaveaK-valueequaltoPVCwrappedwithR5.Theductsandfittingsaretypicallyblueincolor.PVC

ConventionalPVCplasticpipecanalsobeusedinbelow-groundductapplications.Thepipeandfittingsaretypicallywhite,blackorgrayincolor.SunlightcontainsultravioletrayswhichdegradePVC,socaremustbetakenduringconstructiontoprotectthePVCfromexposuretotheelements.TheductworkismadefromthesamematerialasPVCplasticpipeusedinbelow-groundplumbingsystems,whichhavebeeninstalledsuccessfullyintheUnitedStatessincethe1950s.

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FlashingProducts:ManufacturedRoofandPan

Waterintrusioninbuildingwallsistheprimarycauseofprematurebuildingfailure,andtherootcauseofcostlyandtime-consuminglitigationnationwide.Continualwettinganddryingofwallcavitiesnotonlydestroyswoodfibers,butcanalsoprovideabreedinggroundformoldandmildew.Thesewillfoultheappearanceandairqualitysurroundingthemoistarea.Intrusioncanoccurinalltypesofbuildingsandinmostclimates,andtypicallywillinfiltrateatplanarandmaterialjunctionsinbuildings,suchasroof-walljunctions,doorandwindowopenings,andwherearchitecturalfeaturesmeetcladdingandveneer.Flashing,aredundantbarrieratthelocationsmostlikelytoadmitmoisture,haslongbeenthetraditionalapproachtosealingarchitecturalfeaturesandmaterialjunctions.Today,therearenumerousnewflashingproductsavailablethatareabletohandletheincreasingcomplexityofmoderndesigns,whilestillofferingoff-the-shelfconvenience.

RoofFlashingManyroofshavemultipleintersections,suchasvalleys,cricketsandabutmentstoadjacentwalls,whicharepronetowaterleakage.Pre-formedcomponents,suchasdripedges,stepflashings,kick-outdiverters,andspecialtypipeandchimneycaps,providesolutionsthateliminatetheguessworkforspecialtytrades--suchasroofersandsidinginstallers--andgenerallystreamlineconstruction.PanFlashing

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Windowanddoorsillspresentanotheropportunityforwaterleakagefromwind-drivenprecipitation.Industryexpertshavelongrecommendedthattheseareasbeflashedwithwaterdamsatthebackandupthesidesofthesillswithaforwardslopeforpositivedrainage.Therearemanymanufacturedsillpansystemsavailableonthemarkettoday.Oftenmadeofmoldedandsometimesrecycledplastics,theseproductsincludedrainagechannelstodirectwaterawayfromthewindowframe.Theseareavailableinstandardopeningwidthsandcanbecutandcustomizedonsite.Somesystemsincludetrimstripssothatanypartofthesystemvisibleafterinstallationcanbecoveredforaesthetics.

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Quiz3Polyethyleneflooringsystemsthatarespeciallydesignedforuseoverconcretefloorscanalleviate__________problems.

• moisture• vibration• noise

________________isamajorcauseofleakingfoundations.

• Improperdrainagearoundthefoundation• Theuseofpreservative-treatedwood• Sandysoil

TobeeligibleforfloodinsurancethroughFEMA'sNationalFloodInsuranceProgram(NFIP),_____________________.

• thehome'sfoundationmustbeconstructedwithcertainflooddamage-mitigationfeatures

• thehomemustbelocatedina100-yearfloodplain• theapplicantfamilymustqualifyaslow-income

Traditionally,foundationsareprotectedfromfrost-heavingdamagebyplacingthefooting_______thefrostline.

• below• above• at

Frost-protectedshallowfoundationsareprotectedfromfreezingby_________.

• thermalinsulation• aspecialchemicalbondingprocess• installingthembelowthefrostline

Awoodfoundationusingpreservative-treatedlumberresists________.

• allofthese• termites• decay• cracking

Thereismoistureinthegroundfromgroundwaterbeingabsorbed,_____indesertareas.

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• even• except• especially• only

_____________aretelltalesignsofmoistureproblemsinabasement.

• Efflorescenceandmustyodors• Termitesandinfiltrationoftreeroots• Dustandspiders

Avaporbarriercanreducetheinfiltrationof____________.

• allofthese• mold• radon• moisture

Wheninstalledproperly,plasticductworksystemsarewatertightandairtight,andcanwithstandtemperaturesupto______.

• 150?F• 85?F• 32?F

ModularBlockRetainingWallSystems

Modularblockorsegmentalretainingwallsemployinterlockingconcreteunitsthattiebackintotheearthtoefficientlyresistloads.Thesepre-engineeredmodularsystemsareanattractive,economicalanddurablealternativetostoneandpouredconcreteretainingwalls.Theinherentdesignflexibilitycanaccommodateawidevarietyofsiteconstraints,projectsizes,andaestheticpreferences.Individual(andusuallyidentical)precastconcreteunitsinterlock,offset-stack,orareplacedstructurallyindependentofeachotherandanchoredintothebackfill.Theseindependenttiersystemsareadvantageousforseismicareas.Thecomponentsofacompletesystemcanincludefoundationsoil,levelingpad,precastconcreteunitsofhigh-strengthconcrete,shearpins(ifunitsdon'tinterlock),multiple-

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depthwalls,andadditionalsoilreinforcement,suchasgeotextile,welded-wirefabric,anddead-mananchors(ifthewallisoveracertainheight),retainedsoil,anddrainagefill.

Somesystemshaverelativelyshallowunits,whileothershaveunitswithatailfordeepembedmentfortallerandmoreverticalwalls(wallsareneverperfectlyvertical).Thesoilreinforcementconsistsofhorizontallayersthatextendintothebackfill.Beinggravitystructures,thesesystemsrelyontheirownweightandcoherentmasstoresistoverturnandslidingforces.Thesegmentalfeatureaffordsthewallapermeabilitytorelievehydrostaticpressure,solessmaterialisrequiredforresistance.Becausetheyareconsideredflexiblestructures,thefootingsusuallyneednotreachthefrostline.Somesystemsallowforlandscapingofthewallbetweentiers(dependingonsiteconditions),whileothersaredesignedasstructuralframestobecoveredwithlandscaping.ThesesystemshavebeeninstalledallovertheU.S.;distributorlocationsvarypermanufacturer.

ManufacturedHousingGround-AnchorSystems

Manufacturedhomesarenotusuallyinstalledwithpermanentfoundations,butinsteadsitonshortpiersthatresistmostlygravityloads.Groundanchorsareplatesoraugersimbeddedinthesoilthatlimitlateralbuildingmovementdownthroughtensionmemberstiedbacktothehome'schassis.Inthisway,forcesfromhighwinds,earthquakesandfloodsareresistedthroughthecoherentmassoftheearthactingwiththeanchors.Properlyapplied,thesesystemsareacost-effectivewaytolimitstructuralfailurecomparedtoconventionalmanufacturedhousingfoundations,savinglivesandproperty.Inacompleteground-anchorfoundationsystem,thehouseissupportedbyseveralsteelI-beams,whicharesupportedbyanarrayofshortpiers.Tensilemembers,usuallydiagonal,connectthemainbeamswitheachanchorassembly.Ananchorconsistsofarodbetweentheanchorheadandanchorbase,whichisburied3to9feetintoterrafirma,andallowsthecombinedmassoftheretainedsoiltoresistupliftandlateralforces.Typesofgroundanchorsinclude"mantaray"plateanchors,"rockanchors"forrockembedment,single-anddouble-helixanchorsthatareaugeredintoplace,androdsorchainsthatanchorintoapouredstructuralfill.Tensionmembersmaybesteelrods,strapsorlinkchains.Most

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systemsofferstabilizerplatestolimittheanchorheads'horizontaldisplacement.Themostcommongroundanchorsareauger,orhelix-type,systems.Theyareapplicabletoseveraltypesofpiers,andfeatureanchorswithasingle-ordouble-helixbase,andanoptionallateralstabilizerneartheanchorhead.Thehelixisa4-or6-inchcircularplateintheshapeofashortspiral.Steelstrapsholdthehome'schassistotheanchorheads.Variationsincludesteelrodanchors,whichmaybeencasedinapouredstructuralfillcollar,or"rockanchors,"whichmaybeinstalledinsolidrock.Earth-LokÒisa"mantaray"-typeanchorsystemdesignedforearthquakes.Itfeaturesalargeanchorplate(upto6x6inches)thatcanbedrivenupto18feetintotheground.Theplateisthenrotatedwithagad,orsecondsteelrod,andpulledbacktolock.Agalvanizedthreadedrodholdstheplatetothehome'schassis,whichisclampedtoaseriesofsteelpyramidalsupports.Onlycertifiedcrewscaninstallthesystem.Anothersystem,Ground-LocÒ,makesuseoflinkchainsorall-threadrodstyingthehome'schassisintoananchoringmaterialpouredintoexcavatedcavitiesintheearth.Workingwithpiersmadebyothercompanies,themanufacturerprovidespier-to-chassisclampsandall-threadrodstotiethecarryingbeamstogether.Onemodelconvertsthefoundationtoapermanentfoundation,thusqualifyingthehomeasrealproperty,enablingalow-interestmortgage.

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ManufacturedHousingDisaster-ResistantPier

Agoodfoundationgiveshomeownerspeaceofmind.Formanufacturedhomes,oneoptionisadisaster-resistantpiersystem--stoutmembersrigidlyconnectingthehome'schassistoaslab,gradebeam,orarrayofpads.Somesystemsincorporatelateralordiagonalbracingforgreaterresistance.Althoughoftenreferredtoasearthquake-resistantbracing(ERB)systems,manyalsoresisthighwinds,frostheaves,andfloods.Notonlyarethesesystemscost-effectiveinreducingstructuralmovement(comparedtoconventionalmanufacturedhousingfoundations),theycansavelivesandproperty.

Inacompletedisaster-resistantpiersystem,severalrolledsteelbeams(thechassis)aresupportedbyanarrayofstoutadjustablesteelpierswhichareconnectedtoboththechassisandtheconcreteslab,orbasepad,withhigh-strengthbolts.Individualpieradjustmentusuallyconsistsofthreadedrods,oraverticalseriesofholesforacross-bolt.Severalmanufacturersofferasecondarysupportsystem,orseismicisolator,topreventthehomefromdroppingtoolow,shouldthepiersfail.Thiscanbeinstalledseparatelyasaneconomicalretrofit.Optionalbracketsconnectingthepierheadstothefloorjoistshelppreventpiersfromtiltingfromaverticalposition.Piersoverturningfromwindorearthquakeloadsisoneofthemostcommontypesoffailure,andthereisavarietyofremedies.Manysystemsusepyramidalpierssecuredtopadsatthebaseandtolockingdevicesatchassisbeams.Thepierismadeofsteelanglesthatmeetatacollarholdinganadjustingbolt.Onesystemembedsthepierbaseinaconcrete"foot"pouredintoageotextileformbag.Anothersystemsubstitutesrecycledplasticpierpadsforpermanent,pressure-treatedwoodorconcretepads.Othersystemsinstallpiersonprecastgradebeamsandbroadpads.Thepierbaseissecuredtoawidehorizontalsteelplateorframetodistributethepier'sbaseloadoverabroaderarea.Thepierhasasquarecross-section.Somesystemsfeaturerigidsteelanglestrutsandcross-bracingtostabilizeadjacentpiers,triangulatingtheloads.Piersystemretailerstendtospecializeinretrofitting,whilewholesalerstrytodealexclusivelywithnewconstruction.Distributorlocationsvarybymanufacturer.Manypier

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unitsareshippedatleastpartiallyassembled,soshippingcostsmaybehigh.Leadtimevariesfromtwodaystoabouttwoweeks.

PrefabricatedStormShelters

Stormshelterscanhelpreducetheriskofinjuryanddeathcausedbytornadoesandhurricanes.Prefabricatedshelters,designedtowithstandthehighwindandflyingdebrisofCategory5hurricanesandF5tornadoes,areavailableforin-homeandexteriorinstallation.Ready-to-installexteriorconcrete,metalandfiberglassstormsheltersareavailableforlow-profilein-groundinstallationonflatandslopedterrains.In-homesheltersareanchoredtothehome'sfoundation,andcomeinavarietyofmaterialsandconfigurations.Mostin-homeunitscandoubleasfunctionallivingspace.Stormsheltersvaryinsize,withatypicalsizeabout6x8feet.FEMA,theFederalEmergencyManagementAgency,recommends6squarefeetofareaperperson,andameansofventilatingthespaceisrequired.Handicap-accessiblemodelsareavailable.Manufacturersoffervarioussizes,accessmethods,andelementswhichcanincludecarpeting,seating,andanemergencyjacktoremoveexitdoorobstructions,amongotherfeatures.

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