A Guide to the Repair of Historic Roofs - Dublin City Council

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ROOFS A GUIDE TO THE REPAIR OF HISTORIC ROOFSCorrugated ironOther roofing materialsCorrugated-iron sheet was first patented in England in1828 and was used in Ireland for the cladding of bothroofs and walls from the 1860s onwards. By this datemost of the sheet was in fact galvanised corrugatedsteel rather than rolled sheet iron, but it is genericallyreferred to as iron.Historically, corrugated iron in Ireland had a regularwave pattern. Corrugated sheets allow for theoverlapping of individual sheets by as little as onecorrugation. The sheets were fixed to the structuralframework using washers and galvanised bolts or nailsdriven through every third or fourth wave crest. Thesheeting can tolerate low pitches and curved roofforms such as used on hay barns.While corrugated iron was used predominantly onindustrial and farm buildings, Ireland has an array ofcorrugated-iron building types, some of themlandmark structures such as churches, railwaybuildings and boat houses. Some structures wereconstructed entirely from corrugated iron imported asself-assembly kits, fitted onto a timber structure.Corrugated-iron sheeting was also used as a cover onolder thatched roofs to provide increasedweatherproofing of the roof.TIMBER SHINGLESTimber shingles are thinly sawn pieces of timber ofcedar, oak or chestnut, used in roofing or for claddinga feature such as a roof lantern or spire, andsometimes as an external wall cladding. The Romansintroduced timber shingles as a roofing material toBritain. References to their use in Ireland occur as earlyas the eighth century, with Queen Maeve’s palacedescribed as having a ‘roof of shingles’. It is probablethat difficulties in obtaining a ready supply of oak inIreland from the early eighteenth century led to thedemise of the use of timber shingles as a roofingoption. Today only a handful of buildings in Irelandhave shingled roofs.Now usually machine-sawn cedar, chestnut or oak,shingles were traditionally cleft or split. They can befound on the roofs of buildings such as a cottageorné or on decorative architectural features such asroof lanterns or lych gatesCorrugated buildings often came in kit form from asearly as the 1860s, and were used for a variety ofdifferent purposes. Corrugated-iron housing wasmore predominant in the mid-twentieth century.Often seen as temporary, these structures have, inmany cases, lasted over 100 years39
ROOFS A GUIDE TO THE REPAIR OF HISTORIC ROOFSGLAZINGPatent glazing set into the pitch of the roof was oftenused to light the interiors of industrial structures, but isfound on many types of building. It is formed by anarmature of timber or metal set onto the roofstructure on one or both sides of the ridge. Glazingbars extend the full length of each side, glazed inpanes fixed by gaskets. The glazing is weathered to theupper and lower edges of the framework with lead orzinc flashings. Similar construction methods are usedfor projecting roof lanterns.Fully glazed roofs, such as conservatory roofs, wereusually constructed using timber or iron armatures,with glazing bars extending the full length of eachpitch. The glass sat directly onto the framework inpanes of less than a metre long. Each was curved tothe lower edge to throw off water, and to lap over thepane below. The panes were puttied at the sides only.TARRED CLOTH, ASPHALT, CONCRETE ANDASBESTOSTarred cloth was used in the 1850s for cladding thelightweight curved pine ‘Belfast’ trusses constructedon the workers’ houses introduced by the Malcolmsonfamily in Portlaw.Hot rolled asphalt was available from the 1890s and,although used infrequently at that time, it becamemuch more prevalent in the twentieth century, whenflat roofs came into fashion. Asphalt shingles were alsoavailable from the late-nineteenth century andbecame prevalent from the early to mid-twentiethcentury as an economical substitute for natural slateand tiles.Glass roofs, using timber or iron structural elements,were used on conservatories and greenhouses andcan be extensiveSHEET MATERIALS AND METALSOther roofing materials include seamed zinc sheet,which is described as bluish-white in appearance andas a medium hard metal which is reasonably brittle,particularly at low temperatures. From the mideighteenthcentury it was used for roofing and in the1830s it began to be used for sculpture and decorativeelements. Today zinc is used to provide a protectivecoating on steel through processes such as galvanising,sheradising and zinc spraying, or as a fashionableroofing material for contemporary roof profiles.Asphalt shingles were introduced as early as 1890,although their use is more usually associated withbuildings dating from the 1930sConcrete tiles and asbestos sheeting becameprominent in Ireland from the 1930s onwards,particularly on local authority housing schemes.40
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A Guide to the Repair of Historic Roofs - Dublin City Council

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