American Roofing & Metal
Commercial Roofing

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BUR & Modified Bitumen

Built-up Roofing (BUR)

These roofs are commonly referred to as "tar and gravel" roofs, but built-up roof membranes (BUR) actually alternate layers of bitumen and reinforced fabrics that create a finished membrane. These systems have been used for over 100 years.

These system layers are referred to as plies. So a "four ply" roof has four layers of roof membrane construction. Often a base sheet, which is the bottommost ply, will be mechanically fastened. Built-up roofs are considered fully adhered when applied directly to the insulation or roofing deck. 

Modified Bitumen

Modified bitumen (MB) roofing is an asphalt-based design used for commercial buildings with low-slope or “flat” roof structures. These roofing membranes were engineered in Europe in the 1960s, and have been successfully used in the United States and Canada since the mid-1970s. 

MB roofs are flexible, giving designers and installers far more options than just BUR roof. MB roofs may be installed by the torch-application method, "hot-mopped" like BUR or applied with "cold-process" adhesives. A self-adhering sheet is the latest innovation in these types of roofs. By utilizing combinations of certain polymers to modify the underside of a MB sheet, rolls are created with a release paper. As the installer removes the release paper, it adheres to the substrate. This process eliminates the risks associated with torches, hot asphault and is free of volatile organic chemicals (VOC) fumes. 

Learn if a BUR or modified bitumen roof is right for your commercial building by contacting our team.