Single-ply roofing is a term that describes any roof system that is composed of one ply of roof membrane. This membrane can be any one of a number of different materials that may be adhered, mechanically fastened, or ballasted to create your roof system. The application method varies depending on the membrane material. The majority of the materials in single-ply roofing systems did not see application as a roofing membrane as early as the more traditional BUR and mod-bit systems. Single ply roofing now holds an increasing market share of existing and new roofs in North America.