Built up roofing systems, often referred to as BUR, have been utilized in the U.S. for over 100 years. These systems are an incredibly reliable waterproof membrane that is field fabricated with layers of bitumen alternated with reinforcing felts. Commonly referred to as "tar and gravel" roofs, built-up systems redundant layers give it exceptional resistance to water and weather. Johns Manville has been a leader in BUR with 150 years of experience, and offers a complete line of fiber glass felts, including ply and base felts, and mineral surfaced cap sheets.
The bitumen typically used in built-up roof systems is asphalt, coal tar or cold-applied adhesive. The asphalt or coal tar is heated in a kettle or tanker and then applied by mop or mechanical spreader. Cold-applied adhesives do not have to be heated to be applied since these adhesives are solvent-based asphalts.
There are options for built-up roof surfacings that include aggregate, such as gravel, slag or mineral granules, as well as glass-fiber or mineral surfaced cap sheets. Other options are hot asphalt mopped over the entire surface, aluminum coatings or elastomeric coatings.