EPDM roofs are the most popular in the Thermoset Category. These roofs are “rubberlike” and are actually made of large pieces of synthetic rubber. When welded together, the rubber pieces are chemically bonded, forming a single-layer membrane. When stretched, they will elongate, but will return to their original shape when released. EPDM (Ethylene Propylene Diene Monomer) has a typical lifespan of 12-15 years. Hypalon (CSPE) is another Thermoset membrane, with a typical lifespan of 15-20 years.