This ageless roofing system has been in use in the U.S. for over a 100 years. These roofs are commonly referred to as "Tar and Gravel" roofs. Built-up roofs are composed of alternating layers of bitumen and reinforcement fabrics (or plies) that create the finished membrane. Bitumens used in the built-up roof application are either asphalt, coal-tar or with cold applied adhesives. Many surfacing options are considered on built-up roofing, including gravel, mineral surfaced cap sheets, aluminum and elastomeric coatings or smooth surfaced.