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Commercial Roofing Options: Modified Bitumen


Up until not too long ago, modified bitumen roofs were a very high-risk roofing system when it came to installation. The system had to be rolled out, like many single-ply systems, and then had to be heat welded to the roof. This usually included using a blowtorch to heat up the rolled material and the roof surface, and then sticking the material to the roof.

modified bitumen
Modified Bitumen being rolled out on a roof.

This became a problem because, as you can imagine, a blow torch would occasionally be held in one spot for too long, and catch the roof on fire. According to inspectapedia.com, “The main drawback of modified bitumen roofing is the risk of fire during installation. While the risk of fire is low in the hands of trained installers, care must be taken when using torchdown on a wood-frame structure. A number of fires have started with sawdust that has accumulated in empty cavities, such as crickets and parapets. Inspection of the roof for sawdust pockets while it is being framed is advised.”

However, thanks to new developments in the roofing system, the newer materials use a “peel and stick” method which eliminates the need for a blow torch and thus makes the system far safer.

Cons of Modified Bitumen

While modified bitumen roofs can provide some energy savings thanks to their reflectivity, they have one major drawback: they are susceptible to tears and scuffs from just about anything, so the roof needs to be pretty intentionally avoided to make sure that it stays in good shape. With the newer, safer installation methods, this is one of the only drawbacks of the system, overall it is a great roofing option.


Modified bitumen roofs have come a long way in recent years, and they have truly become a great roofing option. There are drawbacks, and they may not provide such robust benefits as spray foam, but they are certainly the right choice in some situations.

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