The Built Up Roof, also referred to as a B-U-R, has a storied history dating back well over 100 years. There are many buildings that have BUR's that are 40+ years old and are still working today. The BUR system originally consisted of cloth rags covered in tar. Over the years there has been many changes to the BUR system. The system now consists of three to five alternating plies of fiberglass felts and hot asphalt or coal tar with a gravel surface adhered in a coating of asphalt or coal tar. Variations with different ply sheets, specialty bitumens and smooth surface coatings are also available. This system is a common and accepted system and many roofing contractors are familiar with the application of the BUR system.