General Contractor Houston Modified Bitumen Commercial Roofing
UNDERSTANDING LOW-SLOPE ROOFING SYSTEMS Very few people are experts on every kind of roofing system. However, the various types of low-slope roofing systems frequently considered for schools basically can be divided into two categories: multi-ply or single-ply. Multi-ply systems generally are bitumen-based (asphalt or coal tar), while single-ply includes polymer and metal systems. Several factors should be considered when selecting a roofing system. The installation design, its application and potential problems are important when determining the optimum system for a particular building. Another consideration is the environment. Although there are no nationwide programs to recycle roofing waste, some materials can be recycled or put to use in other ways.
MODIFIED BITUMEN Description: These roofing systems also use multiple layers of bitumen and reinforcement. However, the products come from the factory with a heavy coating of a polymer-modified bitumen on each side of the reinforcement. The polymers are added to modify the properties of bitumen so that it will be stable and flexible at a wide range of rooftop temperatures. Asphalt commonly is modified with either styrene butadiene styrene (SBS) or amorphous polypropylene (APP). These materials can be assembled into a completed roof by mopping (SBS), torching with a propane burner (APP or SBS), or using special cold adhesives designed for the specific system (SBS or APP). There also are some self-adhering systems available (SBS). The modified bitumen sheets are then assembled into the final roofing product, typically consisting of two or more plies. Some of the plies may be traditional BUR felts. Modified bitumen sheets are the most common type of flashing material in use today on all bituminous membrane systems.
Ideal Application: Modified roofs are very versatile. They can go onto most buildings that have adequate drainage. They are tough and, when damaged, not too difficult to repair using cold repair methods and products similar to BUR, or by torching a patch made of the same type of modified bitumen sheet.
Potential Problems: Open torches on a rooftop create fire risk. As with BUR, the odor of the hot bitumen can be a concern. Care and correct application is necessary, as with other roofing systems. Thus, the installation crews need to be knowledgeable about the type of system being installed.
