Membrane roofing is a type of roofing system for buildings and tanks. It is used to create a watertight roof covering to protect the interior of a building. Membrane roofs are most commonly made from synthetic rubber, thermoplastic (PVC or similar material), or modified bitumen. Membrane roofs are most commonly used in commercial application, though they are becoming increasingly common in residential application.
Synthetic Rubber (Thermoset) – This type of membrane roof is made of large, flat pieces of synthetic rubber or similar materials. These pieces are bonded together at the seams to form one continuous membrane. The finished roof’s thickness is usually between 30 and 60 mils(thousandths of an inch) (0.75 mm to 1.50 mm). The most commonly used thermoset membrane is EPDM. Other types of related materials are CSPE, CR, and ECR. Thermosets are widely used roofing materials due to their ability to withstand damaging effects of sun-rays and chemicals found on roofs.
Thermoplastic Membrane – This is similar to synthetic rubber, but the seams are typically heat-fused (welded) to form a continuous membrane. The 'lap' seams can also be fused with solvents instead of heat, and can be as strong as the rest of the membrane. Other related materials are CPA, CPE, EIP, NBP, PIB, and TPO. Thermoplastic membranes include a reinforcement layer that provides more strength and stability. The most common thermoplastic membranes are PVC (polyvinyl chloride) and TPO (thermoplastic polyolefin).
Modified Bitumen – This type of roofing is an evolution of asphalt roofing. It is made from asphalt and a variety of rubber modifiers and solvents. There are several ways of connecting pieces of this material. In a heat application process the seams are heated to melt the asphalt together and create a seal. There is also hot-mopped application, similar to how conventional built-up roofs are installed. Cold-applied adhesives and self-adhesive membranes are two of the more recent options. Copolymers commonly used to modify asphalt include atactic polypropylene (APP), styrene-butadiene-styrene (SBS), styrene-butadiene rubber (SBR), and styrene-ethylene-butylene-styrene (SEBS).
Advantages Over Asphalt Flat Roofing Systems
These three application types of membrane roofing show distinct advantages over the previously more common flat roofing method of asphalt and gravel. In asphalt and gravel application, it can be very difficult to create a proper seal at all seams and connection points. This can cause a roof to leak early in its lifespan, and require much more maintenance. When installed correctly, newer materials are either seamless, or have seams as strong as the body. This eliminates most of the leakage concerns associated with flat roofing systems.
Repairs for asphalt and gravel roofs can be problematic, largely because it is difficult to locate the exact point of a leak. Newer systems can be patched relatively easily because breaks and leaks are easier to locate.
Originally asphalt roofing required a layer of gravel above it for two reasons. First, asphalt with direct exposure to sunlight degrades much faster, mainly due to the expansion and contraction throughout a day, and also the damage created by UV rays. Secondly, asphalt needs weight above to hold it down, because it sits on the top of a building, instead of being attached to it. Each of the three newer types of membrane roofing systems contain materials that resist expansion and contraction, as well as reflect much of the UV rays. Also, because these membranes either lack seams or have strong seams, what expansion and contraction does occur does not create leaks and breaks at these seams. These newer roofing systems are also attached directly to the top of a building, which eliminates the need for excess weight above.