A built up roof system is commonly referred to as a “tar and gravel” roof. It is called a built up roof because it is actually constructed on site by building up layers of organic felt paper with hot asphalt.
The function of the felt paper is to create a reinforcing mat that increases the roof’s resistance to tearing, stretching and being punctured. The function of the asphalt is to provide waterproofing to the roof system while the gravel acts as ballast and UV protection.
A 60 lb. coat is applied in a standard single layer after the reinforcing mats have been mopped together. If you would like a premium roof system that will last 30 to 35 years, a second coat or double-pour coat can be applied.
Advancements in the science & technology of non-organic reinforcement materials have produced two substitutes for the traditional organic felt paper: polyester and fiberglass. Polyester reinforced roof systems have better puncture resistance and tear strength than traditional felt paper reinforced roof systems. Fiberglass reinforced roof systems provide better tensile strength than the traditional organic felt paper reinforced roof systems.
Built up roof systems that incorporate non-organic reinforcing mats are more costly but add significant value to the customer looking for long-term waterproof performance.
At Westcoast we have years of experience designing and installing various types of 3 and 4 ply built up roof systems.