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Roofing/Flashings/Chimneys

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THE HOME REFERENCE BOOK ©2

ROOFING, FLASHINGS AND CHIMNEYS

INTRODUCTION

1.0Roofing

SLOPEDANDFLAT Therearetwomaincategoriesofroofingsystems:slopedroofsandflatroofs.Roofingprofes-sionalscallthesesteeproofsandlowslopedroofs.Slopedroofingsystemsarenotwatertight;theyshedwaterwithoverlappingshinglesortiles.Flatroofs,ontheotherhand,arewater-tightmembranes.Flat roof isabadname,sinceroofsshouldneverbeperfectlyflat.Theyshouldslopetoallowwatertodrainoffthem,becausewaterstandingontheroofwilldam-agethemembrane,andtheweightofwatercandeflecttheroofstructure.

Thedifferencebetweenslopedroofsandflatroofsistheslope,orpitch,oftheroof.Theslopeisdescribedasaratiooftheverticalriseoverasethorizontalrun.Therunisalwaysdefinedas12feet.Therefore,a6-in-12roofwouldhaveaverticalriseof6feetoverahorizontaldistanceof12feet.Roofswithaslopegreaterthan4-in-12areconsideredsloped.Roofswithaslopebetween4-in-12and2-in-12areconsideredlowslope,androofswithaslopelessthan2-in-12areconsideredflat.

Justtomakeitconfusing,professionalroofersdescribeanythingwithaslopeofmorethan2-in-12assteeproofing.Anythinglessislowslopedroofing.

1.1AsphaltShingles(CompositionShingles)

DESCRIPTION Asphaltshingles(alsocalledcompositionshingles)arethemostcommonroofingmaterialusedtoday.Theshinglesconsistofasphalt-impregnatedfeltpaperorglassfibermats,coatedwithalayerofasphaltandcoveredwithgranularmaterial.

The primary purpose of a roof is to protect the building from rain, snow, sun and wind. Roofs also affect the appearance of a building. Roofs provide some mechanical protection against falling objects, although hail damage for example, is common. Roof coverings are not intended to keep out the cold. Most roofs are very poor insulators.

3THE HOME REFERENCE BOOK ©

ROOFING, FLASHINGS AND CHIMNEYSRO

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LIFEEXPECTANCY Asphaltshingleswerehistoricallyclassifiedbyweight.Today,asphaltshinglesareclassifiedby the manufacturer’s warranty. They are known as 15-year, 20-year, 25-year, 30-year or35-yearshingles.Modernshinglesareavailableinvarioustexturesandpatterns.Whileshingleswithlongerwarrantieswillgenerallylastlongerthanshingleswithshorterwarranties,thewarrantyperiodshouldnotbeconsideredaguaranteeofservicelife.

WEARFACTORS Regardlessofthetypeofshingleused,therearetwosignificantfactorswithregardtowear–exposureandslope.Sunlightisoneofthebiggestenemiesofasphaltroofsandinmanyareas,thesouthandwestexposureswearoutthefastest.Thesteepertheslope,thelongertheshingleswilllast.

Asasphaltshingleswear,theylosetheirgranularcovering.Thegranularmaterialprotectstheshinglesfromultra-violetlight.Asgranuleswearoff,theshinglesdryoutandbecomebrittle.Theycrack,buckle,andcurl.Shingleswearoutfirstwherethegranularmaterialislost.Thismay be due to heavy foot traffic, abrasion from tree branches, erosion from downspoutsdischargingontotheroofsurface,ormanufacturingdefects.

SELF-SEALING Mostasphaltshingleshaveself-sealingstrips,astripofasphaltrunningacrossthemiddleof SHINGLES theshingle.Theshingleaboveoverlapsthelowershingle,withthebottomedgecoveringthis

strip.Whenthesunwarmstheroofsurface,thetwoshinglessticktogether.Thisprotectstheshinglesfrombeingblownoffinaheavywind.Shingles installedincoldweatherdonotsealthem-selves until the weather warmsup. They are vulnerable to winddamageduringthisperiod.

SHINGLESAND Conventional asphalt shingles ROOFSLOPES can be used on a slope as low

as 4-in-12. Shingles can also beuseddowntoaslopeof2-in-12if the roof is first covered withnon-perforated, asphalt-satu-ratedfeltpapersorawaterproofmembrane. The felt papers areoverlapped by 50% and thesection at the eaves (from thebottom edge up to 24 inchesbeyond the exterior wall) iscemented in place to provideextra protection. After con-struction,youcan’ttellwhetherthis was done, especially sincetheshinglesthemselvesmaybecementeddown.

In the past, special shinglesweremadeforthisapplication.Thesearenolongerused.



RE-ROOFING Whileitisbettertoremoveoldroofingbeforere-roofing,asecondlayerofshinglescanbeinstalledoverone layerofshingles ifthe layerbeingcovered isrelativelysmoothandflat.Longernailsmustbeused.Iftherearealreadytwolayersofshinglesontheroof,allshinglesshouldberemovedbeforere-roofing.

Asphalt shingles are often installed over a single layer of wood shingles or slate shingles;however,thenewshingleswillperformbetterandlastlongeriftheoldroofingmaterialsareremoved.

1.2WoodShinglesandShakes

DESCRIPTION Woodshinglesaremachinecut.Theyaretypicallysmaller,thinnerandmoreuniformthanwoodshakes. Traditionally, wood shakes were hand split or mechanically split, although machine-sawnshakesarealsoavailable.Woodshakesarethickerandsplitshakeshaveamuchmoreunevensurface.Mostwoodshinglesarecedar;however,redwoodandpinearealsoused.

Woodshinglescanbeusedonroofswithaslopeaslow as 3-in-12; however, 6-in-12 or more is recom-mended. Wood shingles vary in length between16 inchesand24 inches.Onagoodquality instal-lation, no more than one-third of each shingle isexposedtotheweather.

Shakesmaybeupto24incheslong,withnomorethan half of the shingle exposed. Shakes typicallyhave heavy building paper interwoven with theshakes to prevent wind driven rain and snowgettingintotheroofbetweentheshakes.



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LIFEEXPECTANCY The life expectancy of good quality wood shingles is generally 30 to 40 years; however,lowqualityshinglesdeterioratebadlyin15to20years.Therateofweardependslargelyonexposure(theamountofshinglewhich isexposedtotheweather), theslope(thesteeperthebetter),thegradeofshingle(therearefour),andtheamountofsunandshadetheysee.Sunlight dehydrates the shingles, resulting in splitting and cupping of the shingles. Someshingles‘burnthrough’,withholesdevelopingasaresultofexposuretothesun.

Toomuchshadeandmoistureallowsmosstogrow.Thiscanleadtorot.Woodshinglesandshakesmaysuffermechanicaldamagefromtreebranches,foottraffic,snowshovelling,etc.Anotherfactoraffectingthelifeofwoodshinglesistheirabilitytodryquickly.Woodroofingoverspacedsheathingboardshaslotsofairmovementonthebackoftheshinglesorshakes,promotinguniformdrying.Thishelpsextendthelifeoftheroof.Woodroofingappliedoverplywoodsheathingdoesnotdryasquicklyoruniformly.Someexpertssaytheuseofplywoodwillhalvethelifeofwoodshingles.

ROOFTUNE-UP The shakes or shingles may deteriorate at different rates. The roof’s life can be extendedbyseveralyearsbycarryingoutarooftune-up.Thistypicallyinvolvesspotreplacementofdamagedshakesorshingles(oftenlocatedonthehipandridgecaps)aswellastheadditionofmetalshimsunderanysplitshakesorshingleswherethesplitislocateddirectlyoveranadjacent keyway (the vertical joint between individual shakes or shingles). The tune-upshouldalsoincludearoofcleaningifthereismossand/oralgaegrowth.

Itisimportanttokeepwoodroofingclearoforganicdebris,mossandalgaebuilduptoextendits life. High pressure washing is not recommended as it may damage the roofing. Lowpressurewashingmaysuccessfullyremoveloosematerialwithoutdamagingtheroof.Theroofingcanthenbesprayedwithacombinationmosskillerandnon-toxicdetergenttokillanymoss,algaeorfungus.Aheavyrainwillusuallyremovethedeadmoss.

Themajorityofwoodroofingiswesternredcedarwhichcontainsnaturaloilsthatresistdecay. There are various treatments available that claim to increase this natural decayresistance.Theseclaimsandtheircostshouldbecarefullyevaluated.

RE-ROOFING Woodshinglesorshakescanbeinstalledoverasinglelayerofasphaltshingles;however,itisbettertoremoveexistingshinglestoallowthewoodroofsystemtobreathe.Woodroofingshouldneverbeinstalledoveranoldwoodroof.

1.3SlateShingles

DESCRIPTION Slateisanaturalsedimentaryrockthatisquarried;thequalitycanvary.Highqualityslateroofscanlast200years.Low-qualityroofsmayfailinlessthan20years.Slateroofsareheavy,weighingthreetofivetimesasmuchasconventionalasphaltshingles.Aslopeofsix-in-twelveormore isrecommendedand,slatesareusually installedwithlessthan50%ofeachslateexposedtotheweather.Theslateabovecoversmorethanhalfoftheslatebelow.



WEARFACTORS Whilesomeslatesareoflowqualityandtendtoflakeandshale,thebiggestproblemwithslateroofsisoftenthenailsholdingtheslatesinplace.Withtime,thenailsrustandallowtheslates to slide out of position. Copper and stainless steel nails last longer than galvanizednails.Onceoneslatehascomeloose,waterruststhenailsholdingnearbyslatesinplace.Goodmaintenanceisimportantonanolderslateroof.Whileitisnotcommonpractice,slateroofsshouldbeinspectedandrepairedatleastannually.Slatesthathaveslippedarere-secured,andslatesthathavecrackedorsplitasaresultofmechanicaldamagearereplaced.Asageneralrule,roofreplacementmakessensewhenmorethan10%isinneedofrepair.

FLASHINGS Theflashingmaterialsdonotlastaslongastheslatesthemselves.Metalflashingsareusedwherevertheroofchangesdirectionormeetsanobstructionsuchasachimney.Whentheflashingsrust,asectionoftheroofmayhavetoberemovedtoinstallanewflashing.Thisisanexpensive proposition. Copperand leadflashingsareexpensive, but last longer thangalvanizedsteeloraluminumflashings.

REPAIRWORK Anotherdifficultywithslateroofsisfindingqualifiedpeopletorepairthem.Sinceslatehasnotbeenusedcommonlyforthepast50years,theirinstallationandrepairisavanishingart.Manyslateroofsthatcanbesavedarereplacedwithmodernroofingmaterials,morefamiliartothemodernroofer.

RE-ROOFING Slateroofsshouldneverbeinstalledoveranotherlayerofroofing.Newslateroofsonhomesarerarebecausetheyaresoexpensive.Installingslateonabuildingnotdesignedforslateoftenrequiresstructuralmodificationstotherooftocarrytheweightoftheslates.



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1.4ConcreteandClayTiles

DESCRIPTION These are high quality roofingsystems with life expectanciesof 50 to 100 years. Like slate,these roofs are heavy, weigh-ing four to five times as muchas asphalt shingles. Modifica-tionstotheroofstructuremayberequiredifreplacingasphaltshingleswithconcrete.

Concrete and clay tiles can beusedonaslopeaslowas4-in-12but as with most roofing sys-tems, steeper is better. Manycurrent standards recommend6-in-12 as a minimum. Theamountofoverlap(exposureofthe tiles) varies depending onthe roof system. Systems witha limited overlap are prone toleakage during wind-drivenrains. Many loose-fitting con-crete and clay tile roofs havea watertight membrane suchas built-up roofing below, toact as a backup. The tiles pro-vide protection against fire,ultravioletlightandmechanicaldamage.



FASTENING Somesystemsarenailedinplacewhileothersusespecialclipsorwireties.Insomeregions,thetilesaremortaredintoplace.Inareaspronetohighwindsandhurricanes,theseheavytilescanbetornoffroofs,becomingdangerousprojectiles.

WEARFACTORS Likeanybrittleroofingsystem,concreteandclaytilesaresubjecttomechanicaldamage,andlike any long-lasting roof system, the fasteners may wear out before the tiles. Dependinguponthedesignoftheroofsystem,theycanbeverydifficulttorepair.

Concreteandclaytilesthatarenotflataremoredifficulttoflash.

RE-ROOFING Concreteorclay tilescannotbe installedoveranother roofingsystem,withtheexceptionofasingle layerofasphaltshinglesoroverabuilt-uproof.Theroofstructuremayrequiremodificationtohandletheadditionalload.



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1.5FiberCementShingles

DESCRIPTION Fibercementshinglesconsistofa mixture of Portland cement,water and fibers. Traditionally,asbestos fibers were used, butsince the 1970s asbestos hasbeen replaced by fiberglass or,more commonly, wood fibers.The type of fiber used in shin-glesisnotdeterminedduringahomeinspection.

LIFEEXPECTANCY Theseshinglestraditionallyhadalifeexpectancyof30to50years,although some newer shinglescarrywarrantiesaslongas60years.Somefibercementshinglesaremadetolooklikewoodshingles.

Fibercementshinglesarebrittleandaresusceptibletomechanicaldamage.Oldershinglesoftendiscolorandpromotethegrowthoffungusormoss.Theyaredifficulttorepairandreplacementshinglesmaybehardtoobtain.

RE-ROOFING New fiber cement shingles are rarely installed. Ideally, existing asbestos cement shinglesshouldberemovedpriortore-roofing.Becauseoftheasbestoscontentofoldshingles,specialprovisionsshouldbemadeforhandlinganddisposingofthematerial.

1.6MetalRoofing

DESCRIPTION Therearemanytypesofmetalroofs.Copper,galvanizedsteel,pre-paintedorcoatedsteel,terneandtinarecommon.Somemetalroofshaveagranularsurfaceembeddedinthefinish.Most metal roofs (particularly copper) are expensive systems, but they last longer thanasphaltshingles.Theycanbeinstalledassheetsorshingles.Sheetsandshinglescanbeusedonslopedroofs;however,flatroofsareonlycoveredinsheets.Sheetmetalroofscanhavedifferenttypesofseamsincludingsolderedandcrimped.



WEARFACTORS Likeanyroofingsystemtherearedisadvantages;seamsmaysplitorbedamaged.Allmetalroofsexceptcopperandpre-paintedorpre-coatedroofsshouldbepaintedonaregularbasis.Metalroofsshouldneverbecoveredwithtarbecausemoisturetrappedbelowthetarcausesrusting.Tarcoveredmetalroofsareusuallyneartheendoftheirlife.Metalroofsaredifficulttorepairandreplacementisoftenthemostpracticalalternative.

Leaksaroundthefastenersarecommon,andfailedfastenersmaymaketheroofingvulner-abletoblowingoffinhighwinds.

RE-ROOFING Moisturetrappedintheoldroofingsystemmaycauseprematuredeteriorationofthenewrooforofthesheathingbelow.Bestpracticeistoremoveoldmetalroofingbeforereroofing.

1.7CorrugatedPlasticRoofing

DESCRIPTION Corrugatedplasticisaspecialtytypeofroofing.Itisasingleply,translucentroofsurfacethatisgenerallyusedoverpatiosandlightstructures.Itshouldneverbeusedoverlivingareasasitisnotconsideredtobetrulywatertight.Corrugatedplasticroofsareweakandshouldneverbewalkedon.Theyaregenerallyconsideredtobelowqualityroofingsystemsthatareeasilydamaged,discolorwithsunlightandleakatthejoints.

RE-ROOFING Thisroofinghastoberemovedbeforeapplyinganewroof.

1.8Built-upRoofing

DESCRIPTION Built-up roofs are commonlycalled tar-and-gravel roofs,even though most modernsystems use asphalt instead oftar.Theyareamulti-plyroofingsystem,consistingoftwo,three,fourorevenfivepliesofroofingfelts with a mopping (coating)of asphalt between layers. Afloodcoatofasphaltisthenap-plied over the top and coveredwithgraveltoreflectultravioletlightandprotecttherooffrommechanicaldamage.Theseroofsarestillcommoncommercially,butarebeingreplacedresi-dentiallywithnewersystemsthatarefasterandeasiertoinstall.

SLOPE Built-uproofsaredesignedforflat(lowslope)applicationsandshouldnotbeusedwithaslopeofgreaterthan3-in-12,unlessspecialasphaltisused.

LIFEEXPECTANCY Two-plybuilt-uproofshavealifeexpectancyoffivetotenyears,whilefour-plyroofsnormallylast15to20years.Sincetherooftypicallyhasafloodcoatoftarandgravel,itisnotpossibletodeterminehowmanypliesexist.Itisalsodifficulttodeterminetheconditionofthemem-braneduetothegravelontop.



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WEARFACTORS Built-uproofsrequireskilltoinstallproperly.Ifmoistureistrappedbeloworwithinthemem-brane,blistersandbubbleswillformandreducethelifeexpectancyoftheroofsignificantly.Alackofgravelcausesrapiddeteriorationoftheroofsurface.Aconditionknownasalligatoringoccursasthesurfacebreaksdownandcracksduetoexposuretosunlight.

DRAINAGE Waterpondingonaflatroofcanshortenthelifeexpectancybyasmuchas50%.Rigidinsu-lationorwooddeckingcanbeusedwhenre-roofingtosculpttheroofsurfacetopromotegooddrainage.Asanalternative,additionaldrainscanbeinstalled.Goodpracticeincludesasecondarydrainforflatroofs.Drainsmaybeguttersorscuppersattheperimeter,orcentraldrainsrunningdownthroughthebuilding.

LEAKS Becauseoftheconstructionofbuilt-uproofs,leaksaredifficulttoisolateandrepair.Awaterstainonaceilingdoesnotnecessarilyindicatealeakimmediatelyabove.Watercantravelasignificantdistancethroughthepliesofaroofbeforeemergingontheinterior.

Becauseofthecomplexityofbuilt-uproofs,itisimportantthatareputableroofer,offeringameaningfulguarantee,beused.

RE-ROOFING While it is common practice to install new built-up roofs over existing built-up roofingsystems,moisturetrappedintheoldroofingsystemmaycauseprematuredeteriorationofthenewmembrane.Bestpracticeistoremoveoldroofingbeforeapplyinganewmembrane.

1.9RollRoofing

DESCRIPTION Rollroofingissometimesknownasselvageroofing.Ittypicallycomesin18or36inchwiderolls.Itconsistsofthesamematerialasasphaltshingles(asphaltimpregnatedfeltscoveredwithgranules).Thesurfacemaybe completely covered withgranules or only 50% covered(designed for two-ply applica-tion).Thematerialismostofteninstalled as a single ply withverylittleoverlap.

LIFEEXPECTANCY This low quality roof coveringhasalimitedlifeexpectancyoffivetotenyears.Thereisanex-ceptiontothisrule.Sometimes,roll roofing is used to protecta built-up roof covering as analternative to gravel. From avisualinspectionitisimpossibletotell.Modifiedbitumenroofingcanbeverysimilartorollroofinginappearance.Thehomeinspectormaynotbeabletodeterminetheroofingmaterial.



WEARFACTORS Becauserollroofingmaterialisinstalledinlongstrips,andbecausethematerialexpandsandcontractswithchangesintemperature,itmaybuckleorwrinkle.Thegranularcoveringbreaksdownquicklyinthewrinkledareas,resultinginlocalizedwearandshortlife.

The material is used on bothsloped roof and flat roofs. It issometimes installedwithafulllayer of roofing cement but ismostoftensimplysealedattheseams or nailed at the edges.Where there is no protectionfor the nails, leaks often occuraroundnails.

RE-ROOFING Moisture trapped in the oldroofing system may cause pre-mature deterioration of thenew membrane. Best practiceis to remove the old roofingmaterialbeforeapplyinganewmembrane.

1.10ModifiedBitumenRoofing

DESCRIPTION Modifiedbitumenmembranesareanalternativetobuilt-uproofs.Polymer-modifiedasphaltisbondedtofiberglassorpolyesterreinforcingtoformsheetsofroofingmembrane.Rollsofthisrubberizedasphaltmembranearetypicallytorchedontotheroof,bonded(moppedin)totheroofwithhotasphalt,oradheredtotheroofusingapeel-and-stickbacking.Thesurfaceof the membrane may be protected from ultraviolet rays by a coating of granules, foil, orpaint.Thesheetsareapproximately40incheswideandusuallyoverlapeachotherbyfourinches.Modifiedbitumenroofsmaybeinstalledaseitherasingleordoublelayersystem.



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LIFEEXPECTANCY Alifespanof15to20yearsistypical.

WEARFACTORS Roofs with ultraviolet protection last longer than those without. Two-ply installations aremoredurablethansingle-ply.Sometypesofmembranesperformbetterinacoldorawarmclimate.Thereisnowaytodeterminethetypeduringahomeinspection.

Seamfailureandinstallationproblemsarethemostcommonissues.Regularfoottrafficcanshortenthelifeexpectancysignificantly.

RE-ROOFING Moisturetrappedintheoldroofingsystemmaycauseprematuredeteriorationofthenewmembrane.Bestpracticeistoremoveoldroofingbeforeapplyinganewmembrane.

1.11Single-PlyMembranes(PlasticandRubber)

DESCRIPTION Anotheralternativetobuilt-uproofingisasingle-plymembrane.Thereareanumberoftheseproductsavailable,oftenusedforhigh-endorcommercialapplications.Thesecanbebrokendownintoplastic-basedmaterialsandrubber-basedmaterials.

Plastic,orthermoplastic,membranesincludepolyvinylchloride(PVC)andthermoplasticpoly-olefin(TPO).Rubberorthermosetmembranesincludeethylenepropylenedienemonomer(EPDM)andbutylrubber(polyisobutylene–PIB).

LIFEEXPECTANCY Thereareawidevarietyofmembraneswithevolvingchemicalcompoundsandanumberofinstallationmethods.Alifespanof15to20yearsiscommon.

LEAKS Seam,flashingandinstallationproblemsarethemostcommonissues.Sincemanyofthesemembranesshrink,properattachmentiscritical.Somesystemscanbedamagedbycontactwithincompatiblematerials,includingasphalt.

RE-ROOFING Whilesomemanufacturersofsingleplymembranesclaimtheirproductcanbeinstalledoverexisting materials, most recommend stripping theold roofoff. Most plasticandsyntheticrubberroofmembranesarenotcompatiblewithasphalt.Theseshouldnotbeinstalledoverbuilt-uproofs.



1.12PolyurethaneFoam(PUF)Roofing

Sprayed-in-placePUFisatwo-partfoammixturesprayedontoroofstructurestoformasingleplyroofingmembrane.ThePUFisprotectedfrommechanicaldamage,ultravioletlightandmoisturebyanelastomericrubbercoating.PUFsystemswerefirstinstalledinthelate1960s.Numerousproblemsinthe1970sgavePUFroofingabadreputationinsomeareas.

LIFEEXPECTANCY Lifeexpectanciesofupto20yearsarenowprojectedforPUFsystems,althoughmanyhavehadprematureproblemsandfailures.

WEARFACTORS CommonproblemswithPUFincludedeteriorationofthePUF,crackingorsplitting,delamina-tionorblistering,pondingduetounevenapplicationandcoatingproblems.

RE-ROOFING AlthoughPUFroofingisofteninstalledoveranoldmembrane,manydonotrecommendthisapproach.Moisturetrappedintheoldroofingsystemwillcauseprematuredeteriorationofthenewmembrane.

1.13OtherRoofCoverings

Therearemanytypesofroofcoveringsonthemarkettoday.Examplesincludecomposite,hardboardandrubbershingles.

1.14CommonProblemswithRoofingSystems

1.14.1ProblemsthatAffectAllRoofs

LEAKS Roofingsystemsconsistofseveraldifferenttypesofmaterialsandflashings.Leaksaremostcommon at joints, seams and intersections with other materials. Water leakage may becausedbyanumberoffactorsoperatingtogetherorindependently.Insomecases,thefailurewillbesignificantenoughtowarrantreplacementoftheroofingmaterials. Inothercases,minorrepairsorimprovementsareallthatarenecessary.

DAMAGE Worn,cracked,split,loose,ormissingcomponentsoftheroofcanresultinleakage.Roofingmaybedamagedbyfoottraffic,hail,raccoonsorotheranimals.Missingshingles/tilesmaybetheresultoffastenerfailure.Localizedrepairsareoftenanoption,butasageneralrule,whenmorethan10to15%oftheroofrequiresrepair,itisbesttoreplacetheroofcovering.

OLD/WORNOUT Asroofingmaterialsgrowold,theylosetheirabilitytokeepwaterout.Asphaltandwoodroofingcracks,curlsandshrinks.Woodroofingrotsorburnsthroughfromthesun.Shinglesortilesmayfalloffasthematerialsorfastenersdeteriorate.Built-uproofingdriesoutandcracks,sometimesreferredtoasalligatoring,becauseoftherandomcrackpattern.Membraneroofsoftenfailatseams.Metalroofsrust.Slatemaydelaminate,andconcretemayspall.

BLISTERS Blisteringisacommonproblemwithasphaltbasedroofs,slopedandflat.Itisusuallycausedbymoisturetrappedintheroofmembrane,androofsoftenleakasblistersbreak.



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LOSSOF Gravelorstonesurfacingprot- GRANULAR ects asphalt-based roofs from MATERIAL the sun. Loss of this material

can lead to quick deteriorationoftheasphaltroofingmaterial,and early failure. This may becausedbywind,downspoutdis-charge,foottrafficoramaterialdefectandisanissueonslopedroofsandflatroofs.

POOR When roofing systems are not INSTALLATION installed properly, the prob-

ability of failure increases.Installationdefectsincludeexposedfasteners,pooralignmentofmaterials,incorrectmateri-als,andtoomanylayersofroofing.

TOOMANY Therearelotsofgoodreasonstostripoldroofingbeforeaddingnew–Thenewroofingoften LAYERS lastslongerandthereisanopportunitytoidentifyandrepairdamagetotheroofsheathing.

Strippingoldroofingaddstothecostofre-roofingandasecondroofisoftenaddedoverafirst.Thisworksbetterwithsomematerialsthanothers,butathird layershouldneverbeaddedoversecond,nomatterwhatroofingmaterialisused.

Asphaltshinglesoverasphaltoroverwoodshinglesarecommondoubleapplications.Longerfastenersareneeded,andthelifeexpectancyofthenewroofmaybereduced.

MANUFACTURING Defectivematerialscanfailearlyintheirlife.Thesedefectsincludecracking,blisteringorpre- DEFECTS matureagingoftheroofsurface.Somedefects,suchascolorvariations,aresimplycosmetic

innature.

VULNERABLE Thetypicalvulnerableareasarewheretheroofchangesdirectionormaterial(forexample, AREAS wheretheroofmeetsachimneyorawall).Onaproperlyinstalledroof,theseareasareflashed.

Particularlyvulnerableareasexistwheretwoormoreflashingsintersect,forexamplewhereachimneyoccursinavalley.

Thingsthatobstructtheflowofwateroffslopedroofsincreasetheriskofleaks.Skylights,chimneysanddormersareexamples.Roofpenetrationsforplumbingstacks,electricalmasts,etc.arealsoweakspots.



FLASHINGS Flashingsareperhapsthemostvulnerableareasoftheroof,asthey represent an interruptioninthesurfaceoftheroof.Theseareaddressedinmoredetail inSection2ofthischapter.

PATCHED/ Areas that have been repairedPREVIOUSREPAIRS arevulnerable.Previousrepairs

indicatepriorproblems.

UNSUITABLE Roofingmaterialsthataresuit- MATERIALS able for one application are

sometimes used for another.Metal shingles designed fora slope of at least 3-in-12, aresometimes used on a flat roof.Built-up roofing is sometimesused incorrectly on a slope of4-in-12. It fails by sliding downtheroofsurfaceovertime.

TREEBRANCHES Trees should be kept trimmed away from roof and wall surfaces. The abrasive action of CONTACTING branchesrubbingagainsttheroofcandamagetheroofsystem.Treelimbstouchingbuildings ROOF alsoprovideeasyaccesstothehomeforpests.

SEVEREWEATHER Weathercancauseanew,perfectly-installedrooftoleakundertherightconditions,includingawind-drivenrainfromanunusualdirection,oraheavysnowfollowedbywarmertempera-turesandrain.Strongwindscandamageroofs,blowingshinglesortilesoffslopedroofsanderodinggravelfrombuilt-uproofs.Hailcandamagemostroofsurfaces.



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1.14.2ProblemsUniquetoSlopedRoofs

ICEDAMMING Icedammingoccurswhensnowandicecollect,oftenattheeaves.MeltingsnowontheupperINCOLDCLIMATES portionoftheroof,warmedbytheattic,cannotdrainproperlyasitistrappedbehindthestill-

frozendamatthecoldeaves.Ifthedamislargeenough,waterwillbackupundertheshinglesandleakintotheeaves,exteriorwallsorbuildinginterior.

Someroofsaremorepronetoicedammingproblemsthanothers.Icedamsaremostcommononlowsloperoofsorroofsthatchangefromahighslopetoalowslope.Thelargestdamstendtoformoverunheatedareas,suchaseaves,porches,andattachedgarages.Icedamsarealsocommonabovepartywallsinattachedhouses.

Icedammingproblemsdonotnecessarilyoccureverywinter.Theynormallyoccurafterperi-ods of heavy snowfall when daytime temperatures are at or slightly above freezing whilenighttimetemperaturesarebelowfreezing.

SOLUTIONS Effectivesolutionstoicedammingproblemsareincreasedattic insulationandventilation.Thesetwomeasuresreducetheattictemperaturesosnowovertheheatedportionsofthehousedoesnotmeltsoquickly.

Heatmayalsoleakintotheatticthroughopeningsintheatticfloor.Potlights,exhaustfans,plumbingstacks,chimneysandatticaccesshatchescanallowheatedairintotheatticunlesstheyarewellsealed.Thisisakeyelementincontrollingicedams.

Heatingductsintheatticshouldalsobewellsealedandinsulatedtoavoidwarmingtheatticandmeltingthesnowabove.



EAVEPROTECTION Whenre-roofing,eaveprotect-ion should be provided alongthelowerpartoftheroof,fromtheedgeuptoroughlytwofeetbeyond the exterior wall. Eaveprotectionisoftenawaterproofrubberized asphalt membrane.Inextremeclimates,metalroof-ing is sometimes used on thelowerpartoftheroof.Themetalis watertight and allows snowand ice to slide off the roof. Ametalorvinyldripedgeflashingwillhelpprotecttheloweredgeoftheroofsheathinganddirectwaterintothegutter.

AVALANCHE Small metal devices that pro- GUARDS trude above roof surfaces

(usually on the lower sectionof roof) are designed to holdsnow on the roof and preventavalanches.Thesearecommononslateroofsandlargerhomesand commercial buildings.Somesaythesemayworsenice-dammingconditions.

HEATINGCABLES Electric heating cables alongroofedgesmaybeusedtopre-vent icedams.Theyhavetobeturned on before snow and iceaccumulate to be effective. Insomecases,theycanaggravateratherthanimproveasituationiftheyareturnedonaftertheicedamhasformed.Heatingcablesarenottestedduringaninspection.



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NOKICKOUT Thisflashingshouldbeprovided FLASHING at the bottom of the roof that

is against the side wall. Wherethe flashing is omitted, watermay get in behind the sidingand cause damage to the wallaround and below the bottomoftheroof.

1.14.3ProblemsUniquetoFlatRoofs

PONDINGON Pondingwateronflatroofsreducesthelifeexpectancybyasmuchas50%.Flatroofsshould FLATROOFS notreallybeflat;theyshouldhaveenoughslopetodrainwater,usuallydescribedas1in50or

2%.Wethinkthatiscuttingitprettyfine,andrecommendmoreslopewherepossible.

Whilepondingismostoftencausedbyinadequateroofslope, itmayalsobetheresultofmissingorcloggedroofdrains.Whenleaksdooccur,theydomoredamageifthereisalargevolumeofwaterpondedontheroof.



BUCKLING, Buckling,wrinklingandopen WRINKLING, seams in membranes may be OPENSEAMS caused by poor installation,

membrane slippage, thermalexpansion or contraction, andmoisture trapped in the roof.These conditions can lead toleaks as the membrane opensupordevelopsholes.

Wrinkles or ridges that createopenings at seams are some-timescalledfishmouths.

2.0Flashings

DESCRIPTION Flashings are designed to keep water out. They are used where dissimilar materials meet,where a material changes direction, at roof penetrations and at joints in materials. Flash-ingsareoftengalvanizedsteel;however,theycanalsobetin,terne(steelcontainingcopper,coatedwithalead-tinalloy),aluminum,leadorcopper.Invalleys,rollroofingmaterialmaybeusedasaflashing.Rollroofingissimilartoasphaltshingles,exceptthatitcomesinrolls,roughly18or36incheswide.

LOCATION Whenarooflinechangesdirection,aridge,avalley,orahipiscreated.Ridgesarehorizontalandarefoundatthepeak.Hipsandvalleysarehighspotsandlowspotsrespectively.

2.1ValleyFlashings

DESCRIPTION Allvalleysshouldhaveflashings.Metalvalleyflashingsarebetterbutmoreexpensivethanrollroofing.Wheretheflashingisvisible,itisknownasanopenvalley.Metalvalleyflashingsaretypically24incheswide;however,muchofthematerialishiddenbytheshingles.Whenroll roofing is used, two layers are installed; one being 18 inches wide, and the top one36incheswide.



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Sometimesavalleyflashingisinstalledandthencoveredwithshingles.Thisiscalledaclosedvalley.Thesemaybeclosedcutorfullywoven.

2.2HipandRidgeFlashings

Flexibleshingles(suchasasphalt)aresimplycutandbentoverhipsandridgestomakethemwatertight.Metal flashings are often used with brittle roof-ing materials (wood shingles, slate, and asbestoscement)attheridgesandhips.Flashingsmayalsobemadefromtheroofingmaterial.Onsomeroofs,theflashingiscoveredbyalayerofshingles.



2.3SlopedRooftoFlatRoofFlashings

Whentheflatroofisbelowtheslopedone,theflatroofingmaterialistypicallyappliedfirstandextendeduptheslope.Theslopedroofingcoverstheflatmembrane.Theremaybemetalflashingusedatthechangeindirection.Whentheflatroofisabovetheslopedroof,ametalflashingprotectsthetopoftheslopedroofingmaterial.Themetalflashingextendsontotheflatroofandiscoveredbytheflatroofmembrane.

2.4RooftoWallFlashings

DESCRIPTION Specialflashingisusedwhenaroofintersectsawall.Theflashingdependsontheconfigura-tionandtheroofingmaterial.Ifthetopoftheroofmeetsawall,acounterflashingcanbeinstalledovertheroofingmaterial.Thismetalskirtcoversthetopoftheroofingmaterialandextendsupthewallbehindthesiding.Onmasonrywalls,themetalflashingislet(embedded)into a mortar joint or sealed to the masonry surface with caulking (the less desirableapproach).



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Whenthesideofaroofendsatawall,twosetsofflashingsareused. L-shaped step flashingsareinstalledbetweeneachlayerofshingles.Theverticalpartex-tendsupthewallandiscoveredby siding or a metal counterflashing. Counter flashings areused on masonry walls, andthetopmaybe let intomortarjoints or sealed to the face ofthe masonry with caulking (alesspermanentapproach).

We looked at kickout flashingsonPage19.



2.5ChimneyFlashings

DESCRIPTION Theflashingsusedonthesidesand downhill portion of thechimneyaresimilar to thewallflashings described above. Theweakest part of a chimneyflashing is the high side, fac-ing up the roof. Water runningdowntheroofmustbedivertedaroundthechimney.Theflash-ings on the high side typicallyextendupatleastsixinchesorone-sixth of the width of thechimney, whichever is greater.Theflashingshouldcontinueupunder the roofing to an equalheight.

When a chimney is more than30 inches wide, a saddle (orcricket)shouldbeusedtodivertwateraroundthechimney.Thisis a small peaked roof that di-rectswateraroundthechimney.

LOCATION Thelocationofachimneyaffectshowproneitistoflashingleaks.Achimneynearthepeakofaroofisbetterthanachimneyatthebottomofaroof,whichisbetterthanchimneyinavalley.

2.6ParapetWallFlashings

The exterior house wall may protrude above theroofline, forming a parapet wall. Where the roofmeetsthewall,typicalwall/roofflashingsareused.Acapflashingshouldalsobeprovidedoverthetopof the wall to prevent water penetration into thewallsystem.



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2.7PlumbingStack/ElectricalMast/ExhaustFlueFlashings

Ametalorrubberflashingisprovidedwhereanythingpenetratestheroof.

PITCHPANS Onflatasphaltroofs,pitchpans (PITCHPOCKETS) are sometimes used. A sheet

metal pan around the stack ormast is filled with pitch or tartoadepthofoneortwoinches.Some experts consider this apoorflashing.



2.8SkylightFlashings

Skylights should be flashed much like chimneys. A skylight should be installed on acurb or box that protrudes above the roof surface (unless the skylight comes with a pre-manufactured flashing assembly). This allows for the installation of proper flashings andlimitssnowaccumulationontheskylightincoldclimates.

2.9DripEdgeFlashings

Thismetalflashingisprovidedalongtheloweredgeofsomeslopedroofs.Itisintendedtoprotecttheroofsheathingandfasciafromwaterdamage.

2.10GravelStopFlashings

On most built-up flat roofs, agravel stop flashing made ofmetalisusedattheperimeters.This metal flashing typicallyhas a low profile and performsseveral functions, includingsecuringandprotectingtheroofmembrane at the edge of theroof,preventingthegravelfromsliding off the roof, and form-ing a drip edge to keep waterrun-off from damaging thewoodfascia.



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2.11RoofVentFlashings

Flashingsarebuiltintomostroofvents.Theflashingslidesundertheshinglematerialonthesidesanduphillportionofthevent.Onthedownhillside,theflashingisexposed,overlappingtheroofingmaterial.Theamountofoverlapofshinglesandflashing,aswellasthequalityoftheinstallationdeterminestheeffectiveness.

CommonProblemswithRoofFlashings

Roofsleakwhenflashingsdon’tdotheirjobproperly.Flashingproblemsareoneofthemostcommonsourcesofroofleaks.Whenre-roofing,werecommendflashingsbereplacedeveniftheyarenotwornout.Itisexpensivetoreplaceflashingspartwaythroughthelifeofaroof.

MISSING,POORLY Themostcommonproblemswithflashingsarethat that theyaremissingornotproperly INSTALLED installed.Poorinstallationincludeslooseormissingcomponents,poorfastening,inadequate

heightorlengthandpoorsealingatthetop.Theillustrationsbelowshowagoodwayandaninferiorwaytoattachaflashingtoabrickwall.

DAMAGED/ Flashingsdeteriorateovertime–rustedmetalandtornmembraneflashingsarecommon. DETERIORATED/ Patchesindicatepreviousissuesandmaysuggestfutureproblems. PATCHED

VALLEY Valleyflashingsareoftendamagedbyfoottrafficorobstructedwithleaves,twigsandpine FLASHINGISSUES needles,forexample.Valleysmaysuffericedamproblemsincoldclimates.Valleysthatare

toolongatthebottommayallowwatertoovershootthegutter.Thisallowswatertocollectagainstthefoundationwall,andmayleadtowetbasementsorcrawlspaces.

ROOF-TO- Where wood siding is used as a counter flashing, it should stop roughly two inches SIDEWALL abovetheroofsurfacesothatthewoodisnotconstantlywet.Woodclosetotheroofsurface FLASHINGS– ispronetorot. INADEQUATE CLEARANCE



SADDLEMISSING Saddles(orcrickets)shouldbeprovidedforchimneyswiderthan30inchestodivertwater aroundthechimney.Amissingsaddlemayresultinroofleaksatthechimney.

PITCHPANS Pitchpansshouldbekeptfullofpitchorasphalttoavoidcollectingwater,whichcausesleak- (PITCHPOCKETS) age.Thesehighmaintenanceflashingsareoftenneglected. ONFLATROOFS

PARAPET Parapetflashingsshoulddrainwaterquickly.Whenwateraccumulatesonthetopsurface, FLASHINGS– prematurerustingandleakagemayoccur. PONDING

SKYLIGHT Leaks are common where there are no curbs or very short curbs. Other common problems FLASHINGS includeincompleteorimproperflashingdetailsaroundtheskylight.

GRAVELSTOP Gravelstopflashingsaresometimesloose,rustedormissingaltogether.Itiscommontofind FLASHINGS theroofmembranepullingawayfromthegravelstop.Thiscanleadtoleaksattheroofedge.

3.0Chimneys

MATERIAL Chimneysaretypicallymasonryormetal.Masonrychimneyscanbebrick,blockorstoneandaresometimesstuccoedorparged.Insomeareas,asbestoscementchimneysarecommon.

FLUES Chimneysoftenhavemorethanoneflue.Eachflueisaseparatechannel for the smoke. Eachappliance has a separate flue,with a few exceptions. Twogasfurnacesonthesamefloorwithinahousecanshareacom-mon flue, as can a gas furnaceand a gas hot water heater onthesamelevel.



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FLUELINERS Some flues have masonry exposed on the inside. Unlined chimney flues are common inhousesbuiltbefore1940.Theseunlinedmasonryfluesoftenworkwellforfireplacesandoil-firedfurnaces.Gas-firedfurnacesusually require a liner becausethe cooler exhaust condenses,producing slightly acidic waterthatcandamageunlinedflues.

Flues are typically lined withclay tile, metal, or asbestoscementpipe.Formoreinforma-tiononchimney liners, refer totheHeatingchapter.

VERMINSCREENS Raccoons, birds and squirrelsmay nest in chimneys. Verminscreensonthetopofthechim-neyfluescanbeusedtopreventthis.

CHIMNEYCAP– Thepurposeofachimneycapistoprotectthetopsurfaceofamasonrychimneyfromwater. MASONRY The chimney cap should not be confused with the rain caps that cover chimney flues to

prevent water from enteringthe flues. Chimney caps areusually concrete; however,somearestoneormetal.Acapnormally overhangs the chim-ney sides at least one inch toprotectthechimneyfromwaterdrippingoffthecap.

CHIMNEYCAP– Capsonmetalchimneysarede- METAL signedtokeeprainoutandhelp

promotegooddrawbyprevent-ingdowndrafts.Capsforwoodburning appliances often in-cludeascreentopreventsparksand embers escaping from thechimneytop.



HEIGHT Chimneysshouldbeaminimumofthreefeetabovethepointofpenetration through the roofand two feet higher than any-thingwithintenfeetofthemtohelp ensure good draft. Minorlibertiescanbetakenwiththisrule when considering singleflue metal chimneys for fur-naces. A common solution forfireplaces that draw poorly istoextendthechimneyordivertdowndrafts.

MUTUAL Manyattachedandrowhousessharechimneys.Onechimneymayhaveoneormorefluesfor CHIMNEYS eachhouse.Priortoworkingonamutualchimney,co-ordinationwiththeneighbormakes

sense.Sharedfluespresentasafetyconcern.ThisisdiscussedintheInteriorchapter.

REMOVED Many idle chimneys are re-moved down to below rooflevel during re-roofing. Thiseliminatestheneedforflashing,acommonsourceofproblems.



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CommonProblemswithChimneys

WATERDAMAGE Chimneysoftendeteriorateasaresultofwater.Metalchimneysrust,andmasonrychimneyssufferdamagetomortar,brick,stucco,etc.Thesourceofthewatercansometimesbewind-drivenrainorcondensationwithinthechimney.

Oneoftheby-productsofburn-ing fossil fuels is water vapor.As exhaust gases travel up thechimney, they cool, sometimesreachingthedewpoint,formingcondensation. The water is ab-sorbed into masonry chimneysandsitsontheinteriorofmetalchimneys.Thesomewhatacidicwater droplets cause corrosioninmetalfluesanddeteriorationwithinmasonryflues.

FREEZE/THAW Damagemayoccur inmasonrychimneys because of cyclicalheating in cold climates. Themoisture absorbed into themasonry freezes and expandsas the temperature drops. Thiscauses mortar to deteriorate,bricks to spall and stucco toloosen.Smallamountsofloosemortarcanbereplaced,butex-tensive damage to the mortarorthemasonryusuallyrequiresre-buildingoftheaffectedpor-tionofthechimney.



GAPINLINER Somemasonrychimneyslinedwithclaytilehaveagapintheliner.Thetopfluetileshouldprotrudetwotofourinchesbeyondthetopofthechimney.Ifthetopsectionofclaytilewastooshorttoprotrude(two-footlengths are common), somemasons simply raised the toptile, leavingagapbetweenthetoptwotiles.Aringofdeterio-ration may show up on theexterior of the chimney, corre-spondingtothegapintheclaytileliner.

MISSING In many cases, a proper cap is CHIMNEYCAP– not provided. Bricklayers often MASONRY put a thin coat of mortar over

thetopsurfaceof thechimneyaround the flue. This cementwash has no overhang to keepwaterawayfromthechimney.Overtime,thiscracksandeventuallybecomesloose.Therateofdeteriorationtothetopofachimneythatdoesnothaveacapdependslargelyuponthetypeofmasonryusedtobuildthechimneyandthequalityofthemortar.

CRACKED A cracked cap allows water to CHIMNEYCAP– penetrate the chimney caus- MASONRY ing premature deterioration

and in cold climates, freeze/thawdamage.

DEBRIS Debris can accumulate in thebottomofthechimneyandmayblock off the appliance vent ifnot cleared. Many chimneyshave a clean-out door to allowremovalofaccumulateddebris.



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MISSING Amissingcaponametalchim- CHIMNEYCAP– neycanleadtowaterdamageto METAL thechimneyinterior.Itmayalso

leadtodowndraftproblems.

DRAFTPROBLEMS Short chimneys are prone todowndraft problems, depend-ing on the chimney location,roofshapeandprevailingwinds.

BRACING Tallchimneys,masonryormet-al,shouldbebracedtostabilizethem. The requirements forbracing are not only based onthe height of the chimney butalsoonthewidthanddepthofthechimney.

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