Asphalt BUR Systems Description Koppers will warrant asphalt built-up roofing systems when Koppers Asphalt Glass Fiber Felts are used and when they are a part of an overall Koppers warranted coal tar roofing project, PROVIDED the coal tar portion is at least 80% of the entire warranted roofing project. Certain restrictions may apply to asphalt systems with regard to warranty type and/or term. All asphalt systems shall incorporate Koppers Asphalt Glass Fiber Felt as the reinforcement. Slope requirements are 1/4 inch (2%) per foot minimum and 6 inches (50%) per foot maximum. Koppers does not recommend asphalt built-up roofing systems be applied on slopes less than 1/4 inch per foot (2%), or where water ponds for more than 48 hours after a rainfall. Consult your Koppers representative for copies of asphalt specifications and details.  Return to Built Up Roofing Systems