Asphalt shingles possess an overwhelming share of the U.S. steep-slope roofing market and can be reinforced with organic or fiberglass materials. Although asphalt shingles reinforced with organic felts have been around much longer, fiberglass-reinforced products now dominate the market.
Organic shingles consist of a cellulose-fiber (i.e., wood) base that is saturated with asphalt and coated with colored mineral granules.
Fiberglass shingles consist of a fiberglass mat, top-and-bottom layers of asphalt, and mineral granules. Asphalt shingles' fire resistances, like most other roofing materials, are categorized by Class A, B or C. Class A signifies the most fire-resistant; Classes B and C denote less fire resistance. Generally, most fiberglass shingles have Class A fire ratings, and most organic shingles have Class C ratings.
A shingle's reinforcement has little effect on its appearance. Organic and fiberglass products are available in laminated (architectural) grades that offer a textured appearance. Zinc or copper-coated ceramic granules also can be applied to organic or fiberglass products to protect against algae attack, a common problem in warm, humid parts of the United States. Both types of shingles also are available in a variety of colors.