The History of Built Up Roof Systems
Built Up Roof Systems are the oldest type of roof system which is still installed nowadays – even thought it isn’t done too often. They have been used since the 1840s, and are usually installed in two to five plys, like modified bitumen roofs. BUR roofs tend to come in black, and they have to
be covered by either granules or gravel in order to prevent them from cracking due to the sun’s heat.
Built Up Roofs are installed by hot-mopping. They come in a solid form which has to be broken down in smaller pieces. Once they’re broken down, pieces need to be thrown into a heated kettle, where they get cooked to about 400 degrees. At that temperature, the product turns into a liquid, which will in turn be picked up by a bucket or mop, and then spread across the entire roof. After spreading
the product, it’s important to apply either felt or fiberglass-based paper over it. When the liquid product cools off, it becomes solid again. After the application of the felt paper, it may be a good idea to apply liquid asphalt or pitch over it. The picture represents hot mopping in a modified roof, not in a BUR.
Detail work tends to be completed the same way – details are completed from two to five times based on how many plys there are in the system.
Advantages of BUR Roofs
Here are some of the benefits associated with Built Up Roof Systems:
-Proven system which has been installed for more than 150 years.
-Great puncture resistance
-Proven asphalt performance, since it’s known to go the distance
Disadvantages of BUR Roofs
-High cost, considering two to five plys are needed, which require lots of maerial and labor to install
-Asphalt based roofs will crack and break apart without granules or gravel to protect them from the sun
-Asphalt products don’t last as long as they would a few years ago
-Mop down installations are unsafe for workers and pose serious risks
-Much heavier than single-ply roof systems, due to the fact that two to five plys are applied instead of one
