Modified Bitumen (MB) Roofing Membranes consist of layers of asphalt, modified with either atactic polypropylene plasticizer (APP) or styrene butadiene styrene rubber (SBS) for flexibility. These systems have been in use since the 1970's.

The modified asphalt is then reinforced with layers of a reinforcing fabric, felt or mat during manufacture at a factory. The reinforcing provides strength, stability and reinforcement while the modified asphalt provides flexibility at high and low temperatures. The modified bitumen membrane is available in several thicknesses and is applied over at least one ply a modified bitumen membrane or built up roof. The materials can be smooth surfaced and covered with granules at the factory or coated or graveled.

The APP modified bitumen membranes are torch applied where the SBS version is adhered with hot asphalt or cold adhesives. Some are self-adhesive modified bitumen membranes. Both versions are applied over a single or double layer of a base sheet or BUR. The modifiers provide flexibility through multiple plies of felt and flexible modified bitumen for weather resistance. The flexibility remains at very low and high temperatures.

Granules and coatings over MB membranes can provide reflectivity and also some fire resistance. The granules, smaller round, river washed gravel, when selected, is embedded in either hot asphalt or cold adhesive. This provides UV protection in addition to fire-resistance from flame spread or flying burning objects from other burning buildings. And, vegetative rooftop gardens and photovoltaic panels can be used over these roof membranes.

The system has to be installed to the manufacturers installation instructions, the listing, where applicable, and the building code.

Visit the specific build up membrane pages for more information.

Professional Chicagoland Roofing Council contractor roofing technicians understand the complexity of all types of roofing and get the installation done right the first time. Contact a CRC Contractor that has the equipment, workforce and technology to get your roof done right.

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The Chicagoland Roofing Council Professional Contractors lead the industry in rooftop installations. CRC Contractors work with Vegetative Garden Roofs, Light Colored Reflective Cool Roofs, Ballasted and Gravelled Roofs, Photovoltaic Solar Panel Installation, has protected Chicago Landmarks like McCormick Place, City Hall and more. CRC's main function is to promote the professionalism, culture of efficiency, safety, and productivity, expertise, and reliability of these dedicated contractors who provide the Best Value, Best Roofs, All Year Long.