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What is Membrane Roofing?

B. Turner
B. Turner

Membrane roofing is a type of roofing system designed to reduce the leaks and pooling associated with other roofing materials. This system is gradually replacing the traditional asphalt roof found on many homes and businesses. It is often used on roofs that are flat or very slightly sloped. There are three basic types of membrane roofing systems: thermoset membrane, thermoplastic membrane, and modified bitumen.

With a thermoset membrane roof, sheets of rubber are laid across the surface of the roof with their seams overlapping. The seams are heated, which causes the rubber layers to melt together. Due to the types of rubber used with this system, the heat causes the sheets to form a chemical bond, making the seams as strong as the sheets themselves. The rubber is between 45 and 60 mils (1.14 1.52 mm), making it virtually impenetrable when it comes to water leaks.

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Thermoplastic membrane systems are similar to thermoset systems, but are comprised of PVC or similar materials instead of rubber. The PVC sheets do not bond chemically when heated, but do form a tight seal that keeps water from getting into the seams. These systems are usually not as expensive as thermoset membranes, but may require more frequent maintenance and repairs.

Modified bitumen systems are the most affordable type of membrane roofing, and the most common for residential applications. Rubber compounds and other modifiers are added to traditional asphalt roofing compounds, which is heated with a torch so that it melts and forms a tight seal over the roof. New modified bitumen systems are applied without heat. The asphalt and rubber compounds are applied to sheets in the factory, allowing the installer to simply lay the self-adhesive sheets onto the roof, overlapping the seams to create a watertight seal.

There are several important benefits to using a membrane roofing system instead of traditional roofing materials. A classic asphalt roof is prone to leaks simply due to its construction. Seams are not tightly sealed, and water can seep into the home. Membrane roofing, on the other hand, is virtually seamless, leading to far fewer leaks.

Another advantage to membrane roofing is that there is no need to add a gravel topcoat, which is typically required with asphalt roofs. The gravel is used not only to hold the asphalt in place, but to keep the sun from heating the asphalt too much. Membrane roofing systems are fastened directly to the roof structure, eliminating the need for gravel. In addition, these roofs are often white or light in color, which helps reflect the sun's rays and keep the home cool.

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Discussion Comments


Is it recommended to place playfall decking material directly on the membrane roof vs. a wooden deck? What about maintenance requirements? Where can I find information sheets?

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