What is Modified Bitumen Roofing?
What is Modified Bitumen Roofing?
Modified bitumen is thought of as the evolutionary cousin of the built-up roofing systems (BUR) that have been used on low-slope roofs for more than 100 years. It is made of asphalt combined with polymerized rubber or plastic, then reinforced with fiberglass to create a rugged-yet-flexible waterproof membrane.
Modified bitumen roofing is primarily used on flat or low-slope commercial roofs. Depending on the type and material, these membranes may be installed as part of a two-layer system or as part of a multi-ply system.
History of Modified Bitumen
Modified bitumen first appeared in commercial roofing in the mid-1960s in Europe. Before that time, the conventional roofing system used on most commercial structures was built-up roofing (BUR), a complicated system of alternating layers of asphalt and fabric with a top layer of gravel.
While BUR was a tried-and-true method, it was heavy, costly to install, difficult to repair, and often had trouble holding up against extreme temperatures. By integrating the bitumen with polymers and fiberglass into a simple membrane, the developers of modified bitumen hoped to simplify the roofing process while resolving some of the most common issues with BUR.
Overall, the efforts were successful. Modified bitumen proved to be easier to install while providing enhanced protection compared to BUR systems, even in very cold temperatures. By 1975, modified bitumen was in wide use here in the United States, and today, it has all but replaced BUR as one of the most reliable roofing materials on the market.
Application Methods for Modified Bitumen
Modified bitumen typically comes in membrane form, in rolls that are installed directly onto the substrate via an adhesive. The material may be heat welded, cold-adhered, or in some cases, self-adhered (as with many of Polyglass’ top products that feature ADESO® self-adhering technology).
Some modified bitumen membranes may also be mechanically attached. Most applications call for at least two layers (a base layer and a cap layer), but in some cases, it may be installed in a multi-ply system of three or more layers.
Where and When to Use
With three different types of asphalt roofs how do you decide which one to choose?
BUR
Roofs of essential buildings that need to stay open and operational at all times
BUR is a solution that has been used for over 100 years. The redundant applications allow for increased protection against damage and leaks.
APP
Roofs that need the reliability of a redundant asphaltic system without the odor and labor required for hot mopping.
APP is often used in smaller commercial roofing jobs, especially in urban areas. APP sheets are torched on to the surface below, therefore there is no need for a kettle, buckets or the inconvenience of getting asphalt onto the roof. In addition, APP systems typically consist of fewer plies than BUR jobs, allowing them to be installed faster and with a smaller labor force. Switching from a hot mopped application to a torch application will also reduce the odor around the work location allowing for more comfortable conditions for the workers and building occupants. A CERTA (Certified Roofing Torch Applicator) certification is required for a roofer to use a torch.
SBS
For roofs requiring the reliability of asphalt with more flexible application methods and labor availability.
Like APP, SBS can also be applied utilizing a torch (heat-welding). A CERTA (Certified Roofing Torch Applicator) certification is required for a roofer to use a torch. Many local ordinances also restrict the use of torches on roofs due to their risk as a potential fire hazard. Unlike APP, SBS can be applied in a variety of other ways including hot-mopped, cold-applied or self-adhered. Cold-applied applications are popular because they don’t produce as much odor as hot-mopped and do not require professional certifications like torching. Self-adhered is also a popular method because there is virtually no odor and it is typically faster to install.
EnergyCap™
For buildings that require ENERGY Star® certification or to be LEED® certified.
Utilize an EnergyCap™ sheet with any BUR, APP, and SBS system for projects that require the reliability of asphalt roofing and Energy Star® and LEED® certified solutions.
Tested in the field for decades, GAF asphaltic roofing materials provide durability and performance
Time-Tested
GAF has been selling asphaltic roofing products since 1892 when they created ready-to-lay asphalt roofing rolls which they called “RU-BER-OID roofing.” Ruberoid® as a brand is still around today and GAF’s Mod-bit (SBS and APP) line of products are still sold under this brand name.
Meets Third Party Standards
It is not enough that the products look great. They have to perform great too. This is why GAF thoroughly tests recommended roof assemblies both internally and externally at 3rd party labs such as UL and FM global. So whatever standards are required for a roofing job, GAF has a solution.
Reliable Manufacturer
GAF is a leading manufacturer of protective roofing systems and coatings for the construction industry. Our dedicated teams are positioned to provide guidance and support to the industry. GAF provides roof systems and coating solutions that meet the most rigorous industry standards.
Commitment to Quality
GAF asphalt roofing solutions are specifically formulated with durability in mind. Using only the high-quality raw materials, GAF's products are thoroughly tested to ensure performance.
