Single-ply roofing membranes encompass a large range of roofing products and manufacturers which have proliferated in the roofing industry over the past 20 years. Generally, single-ply membranes are large, flexible, factory-manufactured sheets, usually of a homogeneous material, which may or may not include a reinforcing fabric. These large pieces (4 to 50 ft wide and up to 100 ft long) are then spread out and field-spliced together at the job site to form a continuous sheet of material over the entire roof area. Single-ply membranes can be fully adhered to the substrate with adhesives, mechanically attached with various fastening systems, or laid loose and ballasted in place with 10 to 15 lb/ft2 of concrete pavers or round river rock. Generally, the fully adhered and mechanically attached systems do not require field-applied surface coating.

Single-ply membranes are generally grouped into three categories as defined by their chemical nature:

1. Vulcanized elastomers include EPDM (ethylene propylene diene terpolymer), neoprene (polychloroprene), and epichlorohydrin membranes. They are thermoset materials which cure during the manufacturing process and generally do not include reinforcing fabrics within the membrane. Vulcanized materials cannot be heat- or solvent-welded and therefore use bonding adhesives or tapes to adhere the material to itself.
2. Nonvulcanized elastomers include CSPE (chlorosulfonated polyethylenes, Hypalon, Dupont), CPE (chloronated polyethylene), PIB (polyisobutylene), and NBP (butadiene-acrylonitrile polymer) membranes. They are uncured elastomers that may cure or vulcanize naturally with exposure to weather. Nonvulcanized membranes may or may not include a reinforcing fabric within the membrane. In their uncured state, most nonvulcanized membranes can be heat-welded together. As the membranes cure, bonding becomes more difficult, and only bonding adhesives will work.
3. Thermoplastics include PVC (polyvinyl chloride), modified PVC, and EIP (ethylene interpolymer) membranes. Thermoplastic membranes can be heat- or solvent-welded together and may or may not include a reinforcing fabric within the membrane.