Modified Bitumen (MB) roofing is an asphalt-based, close cousin of the Built-up-Roof (BUR) designed for buildings with low-slope or “flat” roof structures. Engineered modified bitumen roofing membranes originated in Europe in the mid 1960’s and have been used successfully in the United States and Canada since approximately 1975.
Increased resistance to brittleness at cold temperatures, greater flow resistance at high temperatures, and increased elasticity can be achieved by blending synthetic rubberized polymers with asphalt in lieu of modification by the blowing process used for BUR asphalt. There are numerous surfacing options for this system which include a factory applied mineral surface, gravel surface, including “cool roof” coatings which are highly-reflective to save on building cooling costs. Mineral-surfaced MB products are typically furnished with white granules, but are also available in designer colors to match asphalt shingles or to otherwise compliment the building design.
MB gives designers and installers an even broader array of options than BUR. MB may be installed by the torch-application method, or “hot-mopped” like BUR, or applied with “cold-process” adhesives. The latest innovation with MB is the self-adhering sheet. Using special combinations of polymers to modify the underside of the MB sheet, the rolls are manufactured with a release paper. The installer removes the release paper and as the sheet is rolled out, it adheres itself to the substrate. This method eliminates the risks associated with the use of torches, hot asphalt, and is completely free of VOC (volatile organic chemicals) fumes during and after