5/10/2015 RoofWikipedia,thefreeencyclopedia

http://en.wikipedia.org/wiki/Roof 1/10

TheroofsofOlomouc,CzechRepublic

TheroofsofSanCristbaldelasCasas,Mexico

AroofscapeofAntananarivo,Madagascar

RoofFromWikipedia,thefreeencyclopedia

Aroof/ruf/ofabuildingenvelope,boththecoveringontheuppermostpartofabuildingorshelterwhichprovidesprotectionfromanimalsandweather,notablyrain,butalsoheat,windandsunlightandtheframingorstructurewhichsupportsthecovering.[1]

Thecharacteristicsofaroofaredependentuponthepurposeofthebuildingthatitcovers,theavailableroofingmaterialsandthelocaltraditionsofconstructionandwiderconceptsofarchitecturaldesignandpracticeandmayalsobegovernedbylocalornationallegislation.Inmostcountriesaroofprotectsprimarilyagainstrain.Averandahmayberoofedwithmaterialthatprotectsagainstsunlightbutadmitstheotherelements.Theroofofagardenconservatory,protectsplantsfromcold,windandrainbutadmitslight.

Aroofmayalsoprovideadditionallivingspace,forexamplearoofgarden.

Contents

1Designelements2Formofaroof3Partsofaroof

3.1Support3.2Outerlayer

4Functionsofaroof4.1Insulation4.2Drainage4.3Solarroofs

5Galleryofsignificantroofs6Seealso7References

Designelements

Theelementsinthedesignofaroofare:

thematerialtheconstructionthedurability

5/10/2015 RoofWikipedia,thefreeencyclopedia

http://en.wikipedia.org/wiki/Roof 2/10

ShackmadeofdatepalmbranchesatNeotSemadar,Israel

Terminologyofsomeroofparts

Thematerialofaroofmayrangefrombananaleaves,wheatenstraworseagrasstolamininatedglass,copper(see:copperroofing),aluminiumsheetingandprecastconcrete.Inmanypartsoftheworldceramictileshavebeenthepredominantroofingmaterialforcenturies.

Theconstructionofaroofisdeterminedbyitsmethodofsupportandhowtheunderneathspaceisbridgedandwhetherornottheroofispitched.Thepitchistheangleatwhichtheroofrisesfromitslowesttohighestpoint.MostUSdomesticarchitecture,exceptinverydryregions,hasroofsthataresloped,orpitched.Althoughmodernconstructionelementssuchasdrainpipesmayremovetheneedforpitch,roofsarepitchedforreasonsoftraditionandaesthetics.Sothepitchispartlydependentuponstylisticfactors,andpartiallytodowithpracticalities.

Sometypesofroofing,forexamplethatch,requireasteeppitchinordertobewaterproofanddurable.Othertypesofroofing,forexamplepantiles,areunstableonasteeplypitchedroofbutprovideexcellentweatherprotectionatarelativelylowangle.Inregionswherethereislittlerain,analmostflatroofwithaslightrunoffprovidesadequateprotectionagainstanoccasionaldownpour.Drainpipesalsoremovetheneedforaslopingroof.

Thedurabilityofaroofisamatterofconcernbecausetheroofisoftentheleastaccessiblepartofabuildingforpurposesofrepairandrenewal,whileitsdamageordestructioncanhaveseriouseffects.

Formofaroof

Theshapeofroofsdiffersgreatlyfromregiontoregion.Themainfactorswhichinfluencetheshapeofroofsaretheclimateandthematerialsavailableforroofstructureandtheoutercovering.

Thebasicshapesofroofsareflat,skillion,gabled,hipped,archedanddomed.Therearemanyvariationsonthesetypes.Roofsconstructedofflatsectionsthatareslopedarereferredtoaspitchedroofs(generallyiftheangleexceeds10degrees).[2]Pitchedroofs,includinggabled,hippedandskillionroofs,makeupthegreatestnumberofdomesticroofs.Someroofsfolloworganicshapes,eitherbyarchitecturaldesignorbecauseaflexiblematerialsuchasthatchhasbeenusedintheconstruction.

Partsofaroof

Therearetwopartstoaroof,itssupportingstructureanditsouterskin,oruppermostweatherprooflayer.Inaminorityofbuildings,theouterlayerisalsoaselfsupportingstructure.

Theroofstructureisgenerallysupporteduponwalls,althoughsomebuildingstyles,forexample,geodesicandAframe,blurthedistinctionbetweenwallandroof.

Support

5/10/2015 RoofWikipedia,thefreeencyclopedia

http://en.wikipedia.org/wiki/Roof 3/10

TheroofofalibraryinSweden.

AbarkroofinKorea.Seealso:Birchbarkroof

Thesupportingstructureofaroofusuallycomprisesbeamsthatarelongandofstrong,fairlyrigidmaterialsuchastimber,andsincethemid19thcentury,castironorsteel.Incountriesthatusebambooextensively,theflexibilityofthematerialcausesadistinctivecurvinglinetotheroof,characteristicofOrientalarchitecture.

Timberlendsitselftoagreatvarietyofroofshapes.Thetimberstructurecanfulfilanaestheticaswellaspracticalfunction,whenleftexposedtoview.

Stonelintelshavebeenusedtosupportroofssinceprehistorictimes,butcannotbridgelargedistances.ThestonearchcameintoextensiveuseintheancientRomanperiodandinvariantformscouldbeusedtospanspacesupto140feet(43m)across.Thestonearchorvault,withorwithoutribs,dominatedtheroofstructuresofmajorarchitecturalworksforabout2,000years,onlygivingwaytoironbeamswiththeIndustrialRevolutionandthedesigningofsuchbuildingsasPaxton'sCrystalPalace,completed1851.

Withcontinualimprovementsinsteelgirders,thesebecamethemajorstructuralsupportforlargeroofs,andeventuallyforordinaryhousesaswell.Anotherformofgirderisthereinforcedconcretebeam,inwhichmetalrodsareencasedinconcrete,givingitgreaterstrengthundertension.

Outerlayer

Thispartoftheroofshowsgreatvariationdependentuponavailabilityofmaterial.Invernaculararchitecture,roofingmaterialisoftenvegetation,suchasthatches,themostdurablebeingseagrasswithalifeofperhaps40years.InmanyAsiancountriesbambooisusedbothforthesupportingstructureandtheouterlayerwheresplitbamboostemsarelaidturnedalternatelyandoverlapped.Inareaswithanabundanceoftimber,woodenshinglesandboardsareused,whileinsomecountriesthebarkofcertaintreescanbepeeledoffinthick,heavysheetsandusedforroofing.

The20thcenturysawthemanufactureofcompositionasphaltshingleswhichcanlastfromathin20yearshingletothethickestwhicharelimitedlifetimeshingles,thecostdependingonthethicknessanddurabilityoftheshingle.Whenalayerofshingleswearsout,theyareusuallystripped,alongwiththeunderlayandroofingnails,allowinganewlayertobeinstalled.Analternativemethodistoinstallanotherlayerdirectlyoverthewornlayer.Whilethismethodisfaster,itdoesnotallowtheroofsheathingtobeinspectedandwaterdamage,oftenassociatedwithwornshingles,toberepaired.Havingmultiplelayersofoldshinglesunderanewlayercausesroofingnailstobelocatedfurtherfromthesheathing,weakeningtheirhold.Thegreatestconcernwiththismethodisthattheweightoftheextramaterialcouldexceedthedeadloadcapacityoftheroofstructureandcausecollapse.

Slateisanideal,anddurablematerial,whileintheSwissAlpsroofsaremadefromhugeslabsofstone,severalinchesthick.Theslateroofisoftenconsideredthebesttypeofroofing.Aslateroofmaylast75to150years,andevenlonger.However,slateroofsareoftenexpensivetoinstallintheUSA,forexample,a

5/10/2015 RoofWikipedia,thefreeencyclopedia

http://en.wikipedia.org/wiki/Roof 4/10

slateroofmayhavethesamecostastherestofthehouse.Often,thefirstpartofaslaterooftofailisthefixingnailstheycorrode,allowingtheslatestoslip.IntheUK,thisconditionisknownas"nailsickness".Becauseofthisproblem,fixingnailsmadeofstainlesssteelorcopperarerecommended,andeventhesemustbeprotectedfromtheweather.

Asbestos,usuallyinbondedcorrugatedpanels,hasbeenusedwidelyinthe20thcenturyasaninexpensive,nonflammableroofingmaterialwithexcellentinsulatingproperties.Healthandlegalissuesinvolvedintheminingandhandlingofasbestosproductsmeansthatitisnolongerusedasanewroofingmaterial.However,manyasbestosroofscontinuetoexist,particularlyinSouthAmericaandAsia.

Roofsmadeofcutturf(modernonesknownasGreenroofs,traditionalonesassodroofs)havegoodinsulatingpropertiesandareincreasinglyencouragedasawayof"greening"theEarth.Adoberoofsareroofsofclay,mixedwithbindingmaterialsuchasstraworanimalhair,andplasteredonlathestoformaflatorgentlyslopedroof,usuallyinareasoflowrainfall.

Inareaswhereclayisplentiful,roofsofbakedtileshavebeenthemajorformofroofing.Thecastingandfiringofrooftilesisanindustrythatisoftenassociatedwithbrickworks.Whiletheshapeandcolouroftileswasonceregionallydistinctive,nowtilesofmanyshapesandcoloursareproducedcommercially,tosuitthetasteandpocketbookofthepurchaser.

Sheetmetalintheformofcopperandleadhasalsobeenusedformanyhundredsofyears.Bothareexpensivebutdurable,thevastcopperroofofChartresCathedral,oxidisedtoapalegreencolour,havingbeeninplaceforhundredsofyears.Lead,whichissometimesusedforchurchroofs,wasmostcommonlyusedasflashinginvalleysandaroundchimneysondomesticroofs,particularlythoseofslate.Copperwasusedforthesamepurpose.

Inthe19thcentury,iron,electroplatedwithzinctoimproveitsresistancetorust,becamealightweight,easilytransported,waterproofingmaterial.Itslowcostandeasyapplicationmadeitthemostaccessiblecommercialroofing,worldwide.Sincethen,manytypesofmetalroofinghavebeendeveloped.Steelshingleorstandingseamroofslastabout50yearsormoredependingonboththemethodofinstallationandthemoisturebarrier(underlayment)usedandarebetweenthecostofshingleroofsandslateroofs.Inthe20thcenturyalargenumberofroofingmaterialsweredeveloped,includingroofsbasedonbitumen(alreadyusedinpreviouscenturies),onrubberandonarangeofsyntheticssuchasthermoplasticandonfibreglass.

Outerlayer

Slate,Jersey.

Terracottatiles,Hungary.

Thatch,usingricestraw,Japan.

Bananaleaves,Cameroon.

5/10/2015 RoofWikipedia,thefreeencyclopedia

http://en.wikipedia.org/wiki/Roof 5/10

Metalsheeting,Namibia,

repairingthatch,Gasshozukurifarmhouse,Japan.

StoneusedasroofingmaterialinHimachalPradesh,India.

TurfroofinNorway.

Functionsofaroof

Insulation

Becausethepurposeofaroofistoprotectpeopleandtheirpossessionsfromclimaticelements,theinsulatingpropertiesofaroofareaconsiderationinitsstructureandthechoiceofroofingmaterial.

Someroofingmaterials,particularlythoseofnaturalfibrousmaterial,suchasthatch,haveexcellentinsulatingproperties.Forthosethatdonot,extrainsulationisofteninstalledundertheouterlayer.Indevelopedcountries,themajorityofdwellingshaveaceilinginstalledunderthestructuralmembersoftheroof.Thepurposeofaceilingistoinsulateagainstheatandcold,noise,dirtandoftenfromthedroppingsandliceofbirdswhofrequentlychooseroofsasnestingplaces.

Concretetilescanbeusedasinsulation.Wheninstalledleavingaspacebetweenthetilesandtheroofsurface,itcanreduceheatingcausedbythesun.

Formsofinsulationarefeltorplasticsheeting,sometimeswithareflectivesurface,installeddirectlybelowthetilesorothermaterialsyntheticfoambattinglaidabovetheceilingandrecycledpaperproductsandothersuchmaterialsthatcanbeinsertedorsprayedintoroofcavities.SocalledCoolroofsarebecomingincreasinglypopular,andinsomecasesaremandatedbylocalcodes.Coolroofsaredefinedasroofswithbothhighreflectivityandhighthermalemittance.

Poorlyinsulatedandventilatedroofingcansufferfromproblemssuchastheformationoficedamsaroundtheoverhangingeavesincoldweather,causingwaterfrommeltedsnowonupperpartsoftherooftopenetratetheroofingmaterial.Icedamsoccurwhenheatescapesthroughtheuppermostpartoftheroof,andthesnowatthosepointsmelts,refreezingasitdripsalongtheshingles,andcollectingintheformoficeatthelowerpoints.Thiscanresultinstructuraldamagefromstress,includingthedestructionofgutteranddrainagesystems.

Drainage

Theprimaryjobofmostroofsistokeepoutwater.Thelargeareaofaroofrepelsalotofwater,whichmustbedirectedinsomesuitableway,sothatitdoesnotcausedamageorinconvenience.

5/10/2015 RoofWikipedia,thefreeencyclopedia

http://en.wikipedia.org/wiki/Roof 6/10

Flatroofofadobedwellingsgenerallyhaveaveryslightslope.InaMiddleEasterncountry,wheretheroofmaybeusedforrecreation,itisoftenwalled,anddrainageholesmustbeprovidedtostopwaterfrompoolingandseepingthroughtheporousroofingmaterial.

Similarproblems,althoughonaverymuchlargerscale,confrontthebuildersofmoderncommercialpropertieswhichoftenhaveflatroofs.Becauseoftheverylargenatureofsuchroofs,itisessentialthattheouterskinbeofahighlyimpermeablematerial.Mostindustrialandcommercialstructureshaveconventionalroofsoflowpitch.

Ingeneral,thepitchoftheroofisproportionaltotheamountofprecipitation.Housesinareasoflowrainfallfrequentlyhaveroofsoflowpitchwhilethoseinareasofhighrainfallandsnow,havesteeproofs.ThelonghousesofPapuaNewGuinea,forexample,beingroofdominatedarchitecture,thehighroofssweepingalmosttotheground.ThehighsteeplypitchedroofsofGermanyandHollandaretypicalinregionsofsnowfall.InpartsofNorthAmericasuchasBuffalo,USAorMontreal,Canada,thereisarequiredminimumslopeof6inchesin12inches,apitchof30degrees.

Thereareregionalbuildingstyleswhichcontradictthistrend,thestoneroofsoftheAlpinechaletsbeingusuallyofgentlerincline.Thesebuildingstendtoaccumulatealargeamountofsnowonthem,whichisseenasafactorintheirinsulation.Thepitchoftheroofisinpartdeterminedbytheroofingmaterialavailable,apitchof3/12orgreaterslopegenerallybeingcoveredwithasphaltshingles,woodshake,corrugatedsteel,slateortile.

Thewaterrepelledbytheroofduringarainstormispotentiallydamagingtothebuildingthattheroofprotects.Ifitrunsdownthewalls,itmayseepintothemortarorthroughpanels.Ifitliesaroundthefoundationsitmaycauseseepagetotheinterior,risingdampordryrot.Forthisreasonmostbuildingshaveasysteminplacetoprotectthewallsofabuildingfrommostoftheroofwater.Overhangingeavesarecommonlyemployedforthispurpose.Mostmodernroofsandmanyoldoneshavesystemsofvalleys,gutters,waterspouts,waterheadsanddrainpipestoremovethewaterfromthevicinityofthebuilding.Inmanypartsoftheworld,roofwateriscollectedandstoredfordomesticuse.

Areaspronetoheavysnowbenefitfromametalroofbecausetheirsmoothsurfacesshedtheweightofsnowmoreeasilyandresisttheforceofwindbetterthanawoodshingleoraconcretetileroof.

Insulation,drainageandsolarroofing

SnowontheroofsofhousesinPoland.

TheflatroofsoftheMiddleEast,Israel.

Steeplypitched,gabledroofsinNorthernEurope.

TheoverhangingeavesofChina.

5/10/2015 RoofWikipedia,thefreeencyclopedia

http://en.wikipedia.org/wiki/Roof 7/10

Greenroofwithsolarpanels,Findhorn,Scotland.

Solarroofs

Newersystemsincludesolarshingleswhichgenerateelectricityaswellascovertheroof.Therearealsosolarsystemsavailablethatgeneratehotwaterorhotairandwhichcanalsoactasaroofcovering.Morecomplexsystemsmaycarryoutallofthesefunctions:generateelectricity,recoverthermalenergy,andalsoactasaroofcovering.

Solarsystemscanbeintegratedwithroofsby:

integrationinthecoveringofpitchedroofs,e.g.solarshingles.mountingonanexistingroof,e.g.solarpanelonatileroof.integrationinaflatroofmembraneusingheatwelding,e.g.PVC.mountingonaflatroofwithaconstructionandadditionalweighttopreventupliftfromwind.

Roofshapes

Pitchedroofwithdecoratedgable,ChangMai,Thailand.

Sateriroof(withverticalbreakinpitch),Sweden

Mansardroof,countyjail,MountGilead,Ohio.

Conicalroof,NanhaiAcademyinTaipei.

5/10/2015 RoofWikipedia,thefreeencyclopedia

http://en.wikipedia.org/wiki/Roof 8/10

Flatroofs,HaikouCity,Hainan,China.

Flatroof,house,WesternAustralia.

Roundflatroofwithoverhang,Mnster,Germany.

Gradedroofwithasparedspotusedasaroofgarden,Mnster

Galleryofsignificantroofs

ThepolychrometilesoftheHospicesdeBeaune,France.

TheglazedceramictilesoftheSydneyOperaHouse.

ThedomeoverthemihraboftheGreatMosqueofKairoun,Tunisia

ImbrexandtegulatilesonthedomeofFlorenceCathedral.

ThemarbledomeoftheTajMahal.

ThecopperroofofSpeyerCathedral,Germany.

TheleadroofofKing'sCollegeChapel,England.

TheglassroofoftheGrandPalais,Paris.

5/10/2015 RoofWikipedia,thefreeencyclopedia

http://en.wikipedia.org/wiki/Roof 9/10

ConicalroofoftheChteaudeChteaudun'skeep(France,Centre,Chteaudun)

Seealso

AutomobileroofBituminouswaterproofingBuildingconstructionBuildingenvelopeGreenroofCopperroofsMembranestructureMetalroofMetalRoofingAllianceRoofcleaningRoofgardenRooferRoofingfeltSodroofSolarpanelTensilearchitectureTentedroofThinshellstructureTile

History

ListofGrecoRomanroofs

References1. Whitney,WilliamDwight,andBenjaminE.Smith.TheCenturydictionaryandcyclopedia,vol6.NewYork:

CenturyCo.,1901.5,221.Print.2. C.M.Harris,DictionaryofArchitecture&Construction

5/10/2015 RoofWikipedia,thefreeencyclopedia

http://en.wikipedia.org/wiki/Roof 10/10

WikimediaCommonshasmediarelatedtoRoofs.Retrievedfrom"http://en.wikipedia.org/w/index.php?

title=Roof&oldid=660982765"

Categories: Roofs Structuralengineering Structuralsystem

Thispagewaslastmodifiedon5May2015,at18:16.TextisavailableundertheCreativeCommonsAttributionShareAlikeLicenseadditionaltermsmayapply.Byusingthissite,youagreetotheTermsofUseandPrivacyPolicy.WikipediaisaregisteredtrademarkoftheWikimediaFoundation,Inc.,anonprofitorganization.