Built Up Roof Systems
Traditional built-up roofing (BUR) derives its name from the building of a roof on-site using layers of base sheet, interply sheets and cap sheet or other surfacing such as gravel or liquid coating. Hot asphalt (bitumen) is the bonding and waterproofing agent between layers. The use of asphalt in waterproofing applications dates back centuries, making BUR the oldest and most time-proven waterproofing method known. BUR is suitable for most low slope roofing applications.
APP and SBS Modified Bitumen
APP (atactic polypropylene) and SBS (styrene-butadiene-styrene) are modifiers that when added to unblown (unoxidized) asphalt, impart either plastic (APP) or rubber (SBS) characteristics. These additives provide enhanced performance characteristics to traditional asphalt. When coupled with reinforcements, such as polyester (superior elongation abilities) or fiberglass (high tensile strength), they create high-performance roof membranes.
APP modified bitumen membranes are self-adhering when heated using a roofing torch. SBS modified bitumen membranes can be formulated for torch application, but are more commonly applied using hot asphalt or cold SBS modified bitumen adhesive. The result is a BUR system with significantly enhanced performance capabilities. Continuing improvements in technology have also resulted in self-adhering SBS roof membranes.
When a SBS or APP cap sheet is combined with traditional BUR base sheets and interply sheets, the result is a hybrid roof offering the best of each system, multiple plies and superior performance and longevity. All of these systems are excellent roofing choices for industrial, commercial, institutional and residential low-slope roofing.
SBS can be formulated for hot asphalt, cold adhesive, self-adhesive or torch application; APP membranes are typically torch applied only.