Steep-Slope Roof Coverings

These differ from low-slope roof coverings in that on steep-slope roofs water flows rapidly over exposed units to eaves. Many of the low-slope roof coverings described in Art. 12.4 can be successfully used on steep slopes. Many of the low-slope materials, however, become slick when wet. This should be taken into account before they are specified for steep slopes.

Asphalt Shingles

These are composed of a reinforcing mat (organic or glass fiber), a specially formulated asphalt coating, and mineral granules. (Glass-fiber reinforced shingles are sometimes referred to as fiberglass shingles. Organic-reinforced shingles are sometimes referred to as asphalt shingles, which is confusing, for this term properly applies to both the organic and glass-fiber reinforced products.) Most asphalt shingles are manufactured with a self-seal adhesive for wind resistance.

Asphalt shingles are available in a variety of weights. (Weight, however, is not necessarily an indicator of product performance.) Also, they are available in a variety of styles and colors, including three-tab strip shingles (Fig. 12.7), strip shingles, shingles without cutouts, and laminated (architectural) shingles. Laminated shingles have a heavy texture. Shingles that enhance the three-dimensional look by adding shadow lines or shading through use of colored granules are also available.
Glass-fiber reinforced asphalt shingles are specified in ASTM D3462. Organicreinforced asphalt shingles are specified in ASTM D225. Shingles are also available which utilize a polymer-modified bitumen in lieu of the more traditional coatinggrade asphalt.