Durability of Bituminous Built-Up Roofing Membranes

This paper presents an analysis of an industry-wide survey conducted in the winter of 1977-1978 to develop a performance profile for a group of eight common roofing membranes. The analysis shows that: no type of roofing membrane has more than a 50 percent probability of lasting 20 years, membrane durability increases as the number of plies increase, and membranes composed of organic felts have greater durability than membranes composed of asbestos felts. No detectable differences in membrane performance were shown based on geographic differences. These estimates are valid only when the workmanship, flashings, surfacing, insulation, supporting structure, drainage, and other details are adequate.