Commercial buildings with a low slope or flat roof are good candidates for a built up roof membrane known as BUR. This style of commercial roofing has been used since the late 1800's quite successfully and offers many benefits. One positive benefit to using a built up roof is the fact that it is available as part of a fire, wind and hail related roofing system. Another added benefit is the roofing contractor that installs the BUR will generally offer the option of a long term warranty and the top surface option can include a cool roof which is great for conservation energy.
BUR is also known as a tar and gravel roof because it is made up of two to three layers of bitumen and reinforcing fabrics and layered off with gravel. Bitumen is a black, oily material that is an organic byproduct of decomposed materials. It is also known as asphalt or tar. It has been used throughout history as a sealant so its no wonder it has been used for so long as commercial roofing material.
This commercial roofing system uses alternating layers of bitumen, reinforced melt and a top covering of gravel to reflect UV rays, insulate and hold down the roofing material. The average life span of a built up roof is ten to twenty years. Many factors come into play that will determine how long your particular roof will last. The geographical location and weather conditions as well as the slope of the roof and the conditions that the roof was installed under will all will affect the life span of your built up roof membrane.
A three ply built up can last under the best of circumstances for up to fifteen years while a four ply BUR will last twenty years. Of course without the proper maintenance the lifespan of your roof will be shorter than these estimates. In order to extend the lifespan of the roof it is important to maintain the roof through annual inspections. Yearly inspections are a good way to ward off any undetected water damage since asphalt is unacceptable to penetration by water which can get into the building itself if left undetected. Blistering is another common problem brought on by pockets of air and moisture that lie between the layers of asphalt.
However flat roofs are by their very nature high maintenance and prone to leaks and easy penetration which is why they are not recommended for residential homes. Installing a tar and gravel roof is the best method to insulate and protect a flat roof and despite the problems of a flat roof and the maintenance needs of a tar and gravel roof, a BUR system still remains very popular as a commercial application because it is very cost effective and overall works wonderfully.