These roof systems are commonly referred to as "tar and gravel" roofs. BUR systems generally are composed of alternating layers of asphalt and reinforcing fabrics that create a finished membrane. Sometimes a roll with a granulated surface on top is used.
Membranes are hybrids of the built up system, only pre manufactured in the factory. The products come in rolls, and are modified asphalt or coal tar systems with a rubber added for low temperature and elongation characteristics. They can be applied with hot tar, torch, cold adhesives or self adhered with a peel of backing.
Single-ply roofing systems are just that, a single ply of a roofing material made from several types of polymer plastics and rubbers. These three are the most common: TPO, PVC, EPDM.
SPF-based roof systems are constructed by mixing and spraying a two-component liquid that forms the base of a roof system.
Liquid applied coatings are typically made of high-tech polymeric resins such as urethanes, acrylics, silicones, or bitumens which have been modified with polymers. These roofs are applied as a liquid and may or may not rely on reinforcing material, but cure to form a tough, rubber-like membrane. Liquid applied coatings are monolithic (no seams) and are typically considered self-flashing.