Tar & Gravel Flat Roofs
Built-Up Roofing (BUR) or more commonly known to the layman as “tar & gravel” roofing, consists of several plies of #15 Asphalt felt paper (usually 4-5), adhered together with hot bitumen. Another layer of hot asphalt is poured on top and clean crushed stone is embedded into the hot asphalt. The stone is simply there to prevent the sun’s UV rays from deteriorating the asphalt. BUR is heavy and is the most rugged of flat roofing systems. It is not easy to damage a BUR system. Usually we have to take an axe to them to start the removal of and old BUR.
However, it has disadvantages too. Most modern BUR roofs are made of asphalt from crude oil rather than from coal tar as in the old days. Coal tar was a longer lasting product (up to 30 years) with some self-healing properties if damaged. BUR using asphalt from crude oil lasts only about 12-15 years. However, the fact that coal tar is so terribly irritating to the skin and eyes means it has long since passed as a product of any favour with roofers. Asphalt from crude oil is also a labour intensive roof system, and dangerous for the fact that one is working with cauldrons of a liquid that is heated to between 400F – 500F degrees. As such, its popularity is also waning. A disadvantage of going with a BUR system is that essentially the roofing contractor is the manufacturer of the roof system on site. There is no manufacturer warranty on the roof system, just on the component products. There is no manufacturer training or certification of the installers of BUR systems. So it is buyer beware. Typically, BUR warranties are from the roofing contractor and range from 2 to 10 years – but usually 5.