Are Built-Up Roofing Systems Still Viable?
While single-ply systems have captured much of the recent press, bituminous roofing systems (including modified bitumen) still represent a significant share of all low-slope roofing activity. In new construction, hot BUR was reported at 13 percent of the market, cold BUR at 2 percent, and MB at 19 percent, according to the December 2006 issue of RSI magazine. With nearly 150 years of experience and proven performance, BUR systems are still preferred by many building owners and operators, especially if they have an inventory of BUR systems in place. Components of a BUR System Two basic components – felts and bitumen – are laminated in the field (built-up) to form a roofing membrane. The bitumen is usually asphalt (ASTM D-312) or coal tar pitch (ASTM D-450). The bitumen serves as both the system adhesive and the waterproofing agent. Reinforcing felts of glass fiber (ASTM D-2178), organic fibers (ASTM D-226), or non-woven synthetic fibers (ASTM D-5726) provide strength and stability to th