Roof Cements

course. This waterproofs the joint between a sloping roof and vertical wall. This is generally called step flashing. As each course of shingles is laid, a metal flashing shingle is installed and nailed at the top edge as shown. Do not nail flashing to the wall; settling of the roof frame could damage the seal. Wall siding is installed after the roof is completed. It also serves as a cap flashing. Position the siding just above the roof surface. Allow enough clearance to paint the lower edges. Roof Cements Roofing cements are used for installing cave flashing, for flashing assemblies, for cementing tabs of asphalt shingles and laps in sheet material, and for repairing roofs. There are several types of cement, including plastic asphalt cements, lap cements, quick-setting asphalt adhesives, roof coatings, and primers. The type and quality of materials and methods of application on a shingle roof should follow the recommendation of the manufacturer of the shingle roofing. Exterior Basically, exterior roof treatment consists of applying various products, including shingles, roll roofing, tiles, slate, and bituminous coverings. Treatment also includes specific construction considerations for ridges, hips, and valleys. SHINGLES.— The two most common shingle types are asphalt and fiberglass, both of which come in various strip shapes. Asphalt.— Asphalt (composition) shingles are available in several patterns. They come in strip form or as individual shingles. The shingles are manufactured on a base of organic felt (cellulose) or an inorganic glass mat. The felt or mat is covered with a mineral-stabilized coating of asphalt on the top and bottom. The top side is coated with mineral granules of specified color. The bottom side is covered with sand, talc, or mica. Fiberglass.— Improved technologies have made the fiberglass mat competitive with organic felt. The weight and thickness of a fiberglass mat is usually less than that of organic felt. A glass fiber mat maybe 0.030 inch thick versus 0.055 inch thick for felt. The popularity of fiberglass-based shingles is their low cost. The mat does not have to be saturated in asphalt. ASTM standards specify 3 pounds per 100 feet. The Figure 3-22.-A typical 12- by 36-inch shingle. Figure 3-23.-Special shingle application. combination of glass fiber mats with recently developed resins has significantly lowered the price of composition shingles. Strip.— One of the most common shapes of asphalt or fiberglass shingles is a 12- by 36-inch strip (fig. 3-22) with the exposed surface cut or scored to resemble three 9-by 12-2- inch shingles. These are called strip shingles. They are usually laid with 5 inches exposed to the weather. A lap of 2 to 3 inches is usually provided over the upper edge of the shingle in the course directly below. This is called the head lap. The thickness of asphalt shingles may be uniform throughout, or, as with laminated shingles, slotted at the butts to give the illusion of individual units. Strip shingles are produced with either straight-tab or random-tab design to give the illusion of individual units or to simulate the appearance of wood shakes. Most strip shingles have factory-applied adhesive spaced at intervals along the concealed portion of the strip. These strips of adhesive are activated by the warmth of the sun and hold the shingles firm through wind, rain, and snow. Strip shingles are usually laid over a single thickness of asphalt-saturated felt if the slope of the roof 3-18