The felt is used in overlapping layers to form a barrier two to four layers thick. Then, a layer of finely crushed stone is embedded in hot tar over the top to make a really strong and impenetrable roof. A properly installed BUR roof can previous twenty to thirty decades. https://bizbytenews.com/local-roofing-company-in-oswego-your-trusted-partner-for-quality-roof-repairs-and-replacements/