Figure 6-43-A typical building paper and felt on five-ply built-up roof.three standard lengths: 16, 18, and 24 in. The16-in. length is perhaps the most popular. Woodshakes are applied in much the same manner aswood shingles.On flat roofs, the roof covering is usually builtup. BUILT-UP ROOFING consists of severallayers (plies) of felt, set in a hot binder of meltedpitch or asphalt. Built-up roofs are alwaysdesignated by the number of plies they contain.A five-ply built-up roof is shown in figure 6-43,Notice that aggregate surfacing materials,such as gravel, slag, marble, and other suitablematerials,are used in built-up roofing toprovide a good weathering surface and protectthe bitumens from sunlight and external heat.Exterior TrimBefore the installation of the roof sheathingis completed, the exterior finish at and just belowthe eaves of the roof, called CORNICE, can beconstructed. The practical purpose of a corniceis to seal the joint between wall and roofagainst weather penetration. Purely ornamentalparts of a cornice are called trim. Figure 6-44shows a simple type of cornice, used on a roofwith no rafter overhang. A roof with a rafteroverhang may have the “open” cornice shown inFigure 6-44.-Simple cornice.6-29
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