Asphalt shingle roofing (often called “composite roofing”) is made of a “composite” of materials that include a base mat, asphalt on both sides, and granules on top. Asphalt roofs are the most common type of roof found in residential homes due to their versatility, easy installation, and low cost. Early versions were made with an organic base mat of felt, paper, or wood pulp, which was then coated in asphalt and topped with a layer of ceramic granules.
Today, these shingles have been replaced with fiberglass which begins with a fiberglass base reinforced with synthetic resin, coated with asphalt, and topped with granules. The resin and asphalt make the shingle waterproof and hold the granules in place, while the granules protect the shingle from UV damage and add color. It can also help resist algae and fungus growth depending on what additives are added by the manufacturers.