Asphalt Shingle

An asphalt shingle is a thin, flexible roofing unit made from a reinforcing mat that is soaked or coated with asphalt (bitumen) and topped with crushed mineral granules. Shingles are nailed to a solid deck in overlapping rows so that each course sheds water onto the one below. They are among the most widely used roof coverings on houses in North America, and similar products are sold in Europe under the name bitumen shingles.

The product grew out of "asphalt prepared roofing", a rolled material that appeared in the United States in the 1890s. Slate granules were added in 1897, the material was first cut into strips in 1901, and individual shingles were in use by 1903.

Construction

A modern shingle has four parts:

• Mat: originally organic felt (rag, paper or wood fibre); since the 1980s mostly a glass-fibre mat.
• Asphalt coating: often filled with powdered minerals; some products use polymer-modified (SBS) asphalt for flexibility.
• Granules: ceramic-coated stone that blocks ultraviolet light, adds colour and improves fire resistance.
• Back surfacing and sealant: sand, talc or mica on the underside, plus a heat-activated adhesive strip that bonds each course to the next.

Main types

• Three-tab (strip) shingles: single-layer, flat, with two cutouts forming three tabs.
• Architectural (laminated or dimensional) shingles: two or more layers bonded together for a thicker, textured look.
• Designer or luxury shingles: heavier multi-layer products that imitate slate or wood shake.

Weights range from roughly 190 lb per square (about 9 kg/m²) for basic strip shingles to more than 450 lb per square (about 22 kg/m²) for heavy designer products. A "square" is 100 sq ft (9.29 m²) of roof.

Performance and standards

In the United States, the International Building Code requires glass-mat shingles to meet ASTM D3462 and sets a minimum slope of 2:12 (about 9.5°) on a solid deck. Wind resistance is classified under ASTM D3161 and ASTM D7158 (classes D, G and H, up to 90, 120 and 150 mph respectively). Fire performance is tested to ASTM E108 / UL 790, and hail resistance to UL 2218, where Class 4 is the highest rating.

Ageing and lifespan

Heat is the main cause of ageing. Sun and temperature swings drive volatile oils out of the asphalt, the shingle becomes brittle, granules wash off and the mat is eventually exposed. Good attic ventilation and lighter colours slow this process. Typical service lives are commonly given as about 15-18 years for three-tab shingles and 24-30 years for architectural shingles, depending heavily on climate.

End of life

Old shingles are a large waste stream: a 2007 study linked to the US EPA estimated about 11 million short tons of shingle waste per year in the United States. Some is recycled as reclaimed asphalt shingles (RAS) in road paving, although many US states restrict that use.