A class of commercial roof comprised of flexible sheets of compounded synthetic materials that are manufactured in a factory to strict quality control requirements. This is in contrast to built-up roofing, which utilizes hot asphalt and other hazardous components as the roof is constructed in place. Consistent product quality and versatility in attachment methods are two of the inherent attributes of prefabricated sheets. Single-ply roof systems provide strength, flexibility and durability. The two major categories of single-ply membranes are thermoplastics and thermosets.