BUR or built-up roofing got its name from the process of building up a roof. The laying of rigid insulation boards followed by a heavy base sheet material that is topped by multiple plies of fiber glass felts, each layer being applied with a mopped coating of hot melted asphalt. There are several ways used to top this system off for completion of the process. One method is to mop a heavy layer of asphalt and embed in it a spreading of different gravels. Another is to mop a granulated cap sheet for the top covering. The last is to coat the top layer with a cold asphalt emulsion that dries to an aluminum reflective surface.
This built-up roofing system is the traditional method of installing an adequate system for flat roofs. They are hot. They
are dirty. And they fail to provide as a long lasting system due to the costs of increasing the number of felt plies. They do work however, but the typical system consists of one base sheet ply with two felt plies and a layer of gravel. The life expectancy for this described roof is ten to twelve years.
The best way to extend the life of this type of flat roof is to add a couple of additional felt plies during installation. You should insure that there is adequate and positive drainage and eliminate the possibility of “ponding”. The NRCA (National Roofing Contractors Association) stipulates that there should be no more “ponding” of water on a flat roof’s surface after a forty-eight hour time period. Finally, it is important to provide for the addition of walk pads placed across the traffic paths for easy maintenance access to mechanical equipment and drainage portals or any other area suspected of frequent maintenance repairs.