Modified Bitumen Roofing
Considered the most popular roofing system in North America, Modified Bitumen roofing is an asphalt-based product designed for buildings with low-slope or “flat” roof structures. Modified Bitumen roof systems can be installed by heat-welding, hot- asphalt, and cold-process adhesives.
Benefits of Modified Bitumen Roofing include:
- Proven track record of performance with long-term manufacturer warranties available
- High tensile strength for high traffic roofs with multiple penetrations
- Superior waterproofing characteristics for fluctuating temperatures and climates
- A wide choice of top-surfacing including mineral-surfaced products and “cool roof” coatings which are highly reflective to help achieve current energy codes and to keep buildings cooling costs low.
Enhancing Longevity and Performance
One way to enhance the performance and longevity of a low slope roofing system is by applying a modified bitumen roofing membrane. Modified bitumen is asphalt treated to become safer in application and more pliable in use.
A high-performance solution for commercial applications, low slope modified bitumen roofing membranes improve ease of application, increase safety and often promote a cleaner work environment.
Such membranes, developed in Europe in the 1960s and put to use in the U.S. since the 1970s, are influenced by one of two additive types: the APP (atactic polypropylene) and the SBS (styrene-butadiene-styrene).
APP (Atactic Polypropylene)
The advantage of applying an APP low slope modified bitumen membrane is its ability to lend strength while remaining flexible, even during Chicago’s coldest winters.
Applied with a roofing torch, the APP low slope modified bitumen roofing system is heat-welded, adhering to the substrate and sealing itself, resulting in a plastic-like, high-performance membrane.
APP low slope modified bitumen roofing systems resist cracking, blistering, oxidation and damage from the ultraviolet rays of the sun.
SBS (Styrene-Butadiene-Styrene)
The SBS low slope modified bitumen roofing system, applied using either hot asphalt or cold adhesive, results in a more rubber-like membrane.
Some SBS low slope modified bitumen roofing systems start with a base that must be nailed down before being covered with self-adhering membranes, mid-plys and cap sheets.
Unlike APP, SBS low slope modified bitumen roofing requires application of a coating that protects against UV rays.
Special Considerations
Low slope modified bitumen roofing is considered a single-ply rather than a built-up roofing system. However, a base sheet or underlayment still is recommended.
Use of a low slope modified bitumen roofing system also does not eliminate the need for proper drainage and insulation.