Built up Roofing
Built-Up Roofing (BUR) is one of the oldest and most reliable commercial roofing systems for buildings with low-slope or “flat” roof structures. Sometimes called “tar and gravel” roofs. BUR is multiple plies of asphalt roof felts laminated together with bitumen. BUR is made of bitumen-saturated organic-fiber, fiberglass, or polyester felt, with a top coat of asphalt and aggregate. BUR has a very competitive lifecycle cost.
BUR roof systems range from basic to high end. Manufacturer provide longer warranties to property owners based on specific design criteria. Some qualify for decades of “full-value” labor and materials coverage. BUR roofs are not the cheapest option out there for low-slope structures, but the warranty usually puts it as a forerunner. BUR is available as part of a fire, wind, and/or hail rated roofing system.
Ply sheets, the fabrics/layers used on BUR are reinforced with either fiberglass or organic mats. Of the BUR options available, roofs may be as smooth Asphalt built up (Hot or Cold) or ballasted asphalt built up. Ballasted asphalt has been gaining popularity because it gives an excellent finish surface and the materials are a better fire retardant agent. Cold BUR, spray applied or applied with a large squeegee, performs better than hot BUR and is not restricted to weather climates.
Modified Bitumen (MB) roofing has increased resistance to brittleness at cold temperatures, greater flow resistance at high temperatures, and increased elasticity when blending synthetic rubberized polymers with asphalt in lieu of modification by the blowing process used for BUR asphalt.
MB has a number of surfacing options that include “cool roof” coatings (highly-reflective to save on building cooling expenses), factory applied mineral surface, and gravel surfaces. Mineral-surfaced MB products are usually have white granules, but can come in designer colors to match shingles and siding. Long-term warranties are available with several MB manufacturers.
MB is installed with either the torch-application method, or “hot-mopped” like BUR, or applied with “cold-process” adhesives. MB self-adhering sheets use a special combination of polymers to modify the underside of the MB sheet, the rolls are manufactured with a release paper. This method is completely free of VOC (volatile organic chemicals) fumes during and after application.