roofing materials that require continuous supportshould be laid closed (without spacing); however,when wood shingles or shakes are used indamp climates, it is common to have spaced roofboards (fig. 6-39). When plywood roof sheathingis used, it should be laid with the grainperpendicular to the rafter (fig. 6-40).Roof covering materials used for pitched roofsare wood, asphalt shingles, tiles and slate,galvanized iron (GI) sheets, and several other sheetmaterials. For flat or low-pitched roofs, abuilt-up construction is also used. An asphalt-saturated felt underpayment called ROOFINGFELT is applied over the roof sheathing beforethe roof covering is installed. The roofing feltserves three basic purposes: It keeps the roofsheathing dry until the shingles can be applied,it acts as a secondary barrier against wind-drivenrain and snow, and it protects the shingles fromany resinous substance that may be released fromthe sheathing.The method of laying an asphalt-shingle roofis shown in figure 6-41. The roofing rolls areusually 36 in. wide with a 2 in. to 4 in. overlap.The shingles are usually laid with 5 in. exposedto the weather. Figure 6-42 shows installation ofwood shingles. Wood shingles are available inFigure 6-40.-Application of plywood roof sheathing.Figure 6-41.-Application of asphalt shingles: A. Commonmethod with strip shingles; B. Metal edging at gableend.Figure 6-42.-Installation of wood shingles.6-28
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