Built Up Roof System “BUR”
Built Up Roof Systems (BUR) are the oldest roof systems that are still being installed today, even though a new BUR roof installation is rare. They have been installed since the mid 1840’s and, like modified bitumen roofs, are typically installed in 2-5 plys. BUR roofs come in black and need to be covered by either gravel or granules to prevent cracking caused by heat from the sun.
BUR roofs are installed by hot-mopping. The product itself comes in a solid form, and needs to be broken down into smaller pieces. Once broken down, the pieces are thrown into a heated kettle, where it is cooked to 400 degrees. At 400 degrees, the product turns from a solid into a liquid, where it can be picked up by a mop or bucket, and spread across the roof. After the product is spread, felt or fiberglass based paper is applied over the liquid product which, as it cools off, turns back into a solid again. Once the felt paper is applied, another layer of liquid asphalt or pitch can be applied right over it. Note that the picture is of hot mopping a modified roof in, not a BUR.
Detail work is completed in the same fashion, with all details being completed 2-5 times based on the number of ply’s in the system.
Benefits of a BUR Roof
Some of the benefits of Built Up Roof Systems are:
- Proven system that has been installed for over 150 years.
- Proven performance of asphalt, which is known to go the distance.
- Excellent puncture resistance.
Drawbacks of a BUR Roof
Built Up Roof systems have a few disadvantages, which are:
- Very high cost, since there are 2-5 ply’s that require labor and materials to install.
- Asphaltic based roofs rely on gravel or granules for protection from the sun. Without them, Asphalt based roofs crack and break apart.
- Mop down installation methods are very unsafe to the workers.
- Asphalt products don’t last as long as they used to.
- Much heavier than comparable single-ply roof systems, since 2-5 plys of heavy product are installed.
- Very few contractors still have the required equipment to install a BUR Roof.