Modified Bitumen
Local Modified Bitumen
Modified bitumen is a durable roofing system option for flat roofs. It is flexible; expanding and contracting with temperatures, while maintaining weather resistance. It is easy to repair and install. It does not have gravel surfacing – making maintenance and repairs a much easier task. Although its surface typically does not require coating (reduced maintenance costs), an addition of coating may add years to the lifespan of the roofing system.
In the current manufacturing process of modified bitumen, there are two main modifiers that are added: APP (attactic polypropylene) and SBS (styrene-butadiene-styrene), increasing the flexibility and aging ability of the membrane, respectively.
Pros
Common flat roofing system
Asphalt with added modifiers, giving it a rubber-like quality
Surfacings can include mineral granules, copper, aluminum, or aggregate
Usually 1, 2, or 3-ply systems
Yes
Applied with by torch down (which means it is more likely to experience leaks when the proper moisture barrier is not installing underneath the coping cap on parapet walls)
Other problems: inadequate head laps & backwater laps (allow moisture infiltration)
Even cold-applied modbit systems (or ones with under-applied adhesive) can result in moisture infiltration.
Pros
Modified Bitumen is a long standing product in the commercial roofing market. MODBIT, when properly installed, can be an excellent roofing system providing years of performance. However, poor and inconsistent installation methods can often result in poor performance. MODBIT may see failure due to its susceptibility to hail, blistering from poor installation, and deterioration of the material due to ponding water.
MODBIT Weaknesses:
- Hail susceptibility
- Blistering from poor installation
- Deterioration due to ponding water
- Seam failure
