BUR: Built Up Roofing
What Is Built Up Roofing?
Built up roofing, or BUR, is one of the most popular materials use for covering low slope or flat roofs. These roofs have been widely used in the past century and are constructed of numerous layers of a reinforced fabric. Each layer is known as the “ply”. The layers are bound together with bitumen (a binding agent) to form a solid roof. The higher the number of plies there are, the more durable and long lasting the roof will be. Roofers in Omaha, for example, would advise a very high number of plies to withstand the harsh weather seen in Nebraska.
The two types of built up roofing most often used are categorized by the type of bitumen, or binding agent, that is used. They are coal tar, which is manufactured using the waste products from coal production, and asphalt, which is made from the by-products of manufacturing petroleum. When it comes to roofing, Omaha sees enough harsh weather to put any material to the test so coal tar, which is more durable than asphalt, would be a better choice for your flat or low sloped roof. Asphalt is sometimes chosen because it is less expensive than coal tar, but the use of either of these materials may be restricted by environmental laws or regional availability.
When installing built up roofing, the roofers begin by placing a waterproofing layer on the roof deck. They then nail two layers of rubber membrane or building paper to that surface. They are effectively making the roof waterproof before they add any additional BUR plies. The installers will then lay layers of either fiberglass or roofing felt with a layer of coal tar or asphalt applied between each layer. When the layering process is finished the installers will coat the entire surface with a top coat, usually clear glaze or gravel. Built up roofing usually consists of somewhere from three to five plies not including the membrane layers used in waterproofing. Roofers in Omaha may suggest more plies because of the severe weather that occurs in the area.
The main benefits associated with using built up roofing are the low cost of materials as well as installation when compared to the alternative materials such as rubber or metal. Built up roofs are also fairly low maintenance and can be patched quite easily should damage occur. The waterproofing layer with the addition of the plies creates a seal that will be reliably water –tight and free of leaks.
As with anything, built up roofing has its drawbacks as well as benefits. The main drawback is that in areas where the sun is likely to play a large part in the breakdown of roofing (Omaha being one of those areas) the materials used are prone to small cracks. If not repaired the cracks will become worse as time goes on and cause the roof to deteriorate. The materials used in this type of roofing also produce a very unpleasant odor when installing which deters some people.
Today it’s more common that roofers will be removing and replacing BUR roofing, but some people do still elect to have it installed.