Built Up Modified Roofing (BUR) Systems
Torch-down modified bitumen roofs are single-ply rolled roofs impregnated with a mineral-based wear surface. With torch-down systems the adhesive is heated as the material is unrolled.
BUR roofing offers distinct advantages over the previously common flat roofing method which utilized asphalt & gravel. Asphalt & gravel roofs were flat, which caused water to collect, whereas BUR roofing is sloped toward drains or scuppers for drainage. With asphalt & gravel application, it can be very difficult to create a proper seal at all seams and connection points; which can make a roof leak early in its lifespan, and cause it to require much more maintenance. When installed correctly, the newer materials are either seamless, or their seams are as strong as the body; eliminating many of the leakage concerns attributed to flat roofing systems. Repairs on asphalt & gravel roofs can be difficult, chiefly due to difficulty in locating the exact point of a leak. The newer systems can be patched with relative ease, plus breaks and leaks are easier to locate.
Asphalt roofing required a layer of gravel above it for two reasons:
- asphalt directly exposed to sunlight will degrade much more quickly due to the expansion & contraction throughout the day, in addition to damage created by UV rays.
- asphalt needs to be weighed down, because it sits atop a building, rather than being attached to it. The newer types of membrane roofing systems consist of materials that resist expansion and contraction. They also reflect the majority of UV rays. Finally, because these membranes are either seamless or have strong seams, any expansion and contraction that does occur won’t create leaks or breaks at these seams. They are also attached directly to the tops of buildings, and this eliminates the need for extra weight above.