Figure 3-29.-Layout pattern for hip and valley shingles.dependent on heat. Coal-tar pitch roofs are entirelyunaffected by water. When covered by mineralaggregate, standing water may actually protect thevolatile oils.CONSTRUCTION CONSIDERATIONS.—Laying rooting on a flat surface is a relatively easyprocedure. Correctly applying materials to irregularsurfaces, such as ridges, hips, and valleys, is somewhatmore complex.Ridge.— The most common type of ridge and hipfinish for wood and asphalt shingles is the Boston ridge.Asphalt-shingle squares (one-third of a 12- by 36-inchstrip) are used over the ridge and blind-nailed (fig. 3-28,view A). Each shingle is lapped 5 to 6 inches to givedouble coverage. In areas where driving rains occur, usemetal flashing under the shingle ridge to help preventseepage. The use of a ribbon of asphalt roofing cementunder each lap will also help.A wood-shingle roof should be finished with aBoston ridge (fig. 3-28, view B). Shingles, 6 incheswide, are altemately lapped, fitted, and blind-nailed. Asshown, the shingles are nailed in place so that theexposed trimmed edges are alternately lapped.Reassembled hip and ridge units for wood-shingle roofsare available and save both time and money.A metal ridge can also be used on asphalt-shingle orwood-shingle roofs (fig. 3-28, view C). This ridge isformed to the roof slope and should be copper,galvanized iron, or aluminum. Some metal ridges areformed so that they provide an outlet ventilating area.However, the design should be such that it prevents rainor snow from blowing in.Hips and Valleys.— One side of a hip or valleyshingle must be cut at an angle to obtain an edge thatwill match the line of the hip or valley rafter. One wayto cut these shingles is to use a pattern. First, select a 3foot long 1 by 6. Determine the unit length of a commonrafter in the roof (if you do not already know it). Set theframing square on the piece to get the unit run of thecommon rafter on the blade and the unit rise of thecommon rafter on the tongue (fig. 3-29). Draw a linealong the tongue; then saw the pattern along this line.Note: The line cannot be used as a pattern to cut a hipor valley.Built-up RootingA built-up roof, as the name indicates, is built up inalternate plies of roofing felt and bitumen. The bitumenforms a seamless, waterproof, flexible membrane thatconforms to the surface of the roof deck and protects allangles formed by the roof deck and projecting surfaces,Without the reinforcement of the felts, the bitumenswould crack and alligator and thus lose their volatile oilsunder solar radiation.3-25
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