Roofing Work

the covering of buildings and structures with roofing materials. In modern construction the most commonly used roof coverings are those made of roll materials. Coverings made of mastic and piece materials are also used. Roofing work using roll and mastic materials includes vapor insulation of the basic structure by the application of roofing mastics or by cementing one or two layers of roll material (per-gamyn, Ruberoid, glass Ruberoid, or tar paper) to hot or cold mastics; thermal insulation (made of plate, cast, or bulk heat-insulation materials); an intermediate layer; and a roof covering with a protective layer. These operations may be performed at the construction site or at the place of manufacture; in the latter case, all except the uppermost roofing layer are laid out on prefabricated roof structures.

Roof coverings made of roll and mastic materials are applied to smooth, strong concrete, asphalt-concrete, or gypsum-concrete foundations. The material is cemented to the foundation and the layers are glued to one another by bitumen-based and tar-based roofing mastics, depending on the type of impregnation of the roll material used. Roofing mastics are usually prepared at a central location in jet mixers and transported by pumps through piping to the roof. After priming the base, the roll sections are laid out across the slope of the roof (for a roof pitch of up to 15 percent) or along the slope (for a pitch of more than 15 percent). The number of layers of material and the methods of gluing them are determined by the plan. The sections of the roofing carpet are glued in layers in an arrangement of transverse connecting seams 100 mm wide and longitudinal seams 70–100 mm wide. In the case of roof pitches of up to 10 percent, the cement may be applied and the roll materials laid and glued by roofing machines. A protective roofing layer is applied by sprinkling crushed stone (gravel) or other frost-resistant mineral materials (with a coarseness of 3–15 mm) on a layer of tarred or disinfected bituminous mastic.

Roof coverings made of mastic materials are installed in layers on prime-coated bases by means of pneumatic paint spray guns. The mastic is usually applied in four layers, each with a maximum thickness of 5 mm, after the previous layer has dried. Aluminum paint or crushed stone is used for the protective layer.

The most widely used roof coverings made of piece materials (asbestos-cement sheets and slabs, tile, and roofing iron) are roofs made of corrugated and semicorrugated asbestos-cement laid out on a wooden lathwork or on reinforced-concrete, steel, or wooden beams, with the corrugations arranged along the pitch of the roof. The sheets are fastened to the lathwork with galvanized wood screws and nails and to the beams with hooks; each sheet is overlapped by another for one corrugation and for 200–250 mm by a sheet of the row above it. Roofs made of flat asbestos-cement slabs have more seams than roofs made of corrugated sheets, which necessitates a steeper pitch of the roof.

Tile roofing is installed on roofs with a pitch of 45–60 percent. The tile is laid on a continuous lathwork, beginning with the cornice rows, hooking with a slot from the rear side and attaching by wire to nails fastened to the lathwork. Roofs made of sheet steel have little dead load and comparatively low pitch. However, steel roofs are not usually installed in new buildings because of the high consumption of steel and the high cost of maintenance.