Built Up Roofing (BUR), also known as ‘tar and gravel’ is considered the original flat roof system for low-sloped structures. It is typically made of oxidized asphalt and organic felt in at least four off-set layers, with gravel on top to protect the membranes from fire, Ultra Violet light, and wind uplift. This roofing system was often warranted by the installing company.
The declining quality of organic felts and asphalt, lead to alternate products, such as fiberglass, polyester composite felts and rubberized asphalt. The flexible membrane roof systems, with better resistance to expansion and contraction, are the choice of many Government agencies and commercial building owners. These systems are offered with a manufacturer’s warranty.