Built-Up Roofing Systems have been in use in the U.S. and Canada for over 100 years.
Early composition or built-up roofing (BUR) often featured layers of heavy paper covered with pine tar and sprinkled with sand. Documented use of asphalt for roofing, in preference to coal tar, began in the 1870s. However, its use became prevalent as petroleum refining technology improved in the early twentieth century. Asphalt gained preference because it was easier to handle and had a wider functional temperature range than coal tar.
The 20th Century
During the last two decades of the 20th century, a variety of other types of low-slope roof systems began to compete with traditional built-up roofs (BUR). These newer systems included modified bitumen, single-plies, sprayed polyurethane foam, metal panels, and reinforced liquid-applied roof membranes. Liquid-applied roofing was added to the International Building Code, 2012 Edition (IBC 2012) in Section 1507.15. The NRCA has a section and details for this type of roofing in The NRCA Roofing Manual: Membrane Roof Systems.
Built-Up roof systems are commonly referred to as “tar and gravel” or “BUR” roofs. Built-up systems are installed by alternating layers of asphalt or tar and supporting fabrics directly onto the roof. You can choose the number of layers (or plies) that are installed. The final layer of a built-up roofing system consists of a flood coat of asphalt with embedded stone or gravel.
While the modified bitumen systems are related to BUR, the other low-slope alternatives are radically different. Along with new choices of membrane materials, plastic foam roof insulations also emerged in the 1970s. The abundance of materials and applications from which to choose has created a complex and challenging subject matter.
Application Method of BUR
Alternating layers of reinforcing plies of roofing felts bound with asphalt or bitumen are applied to build up the roofing system to the desired level of plies. In a conventional system, gravel or other surface material is then embedded into the top layer of asphalt. In an inverted system, the insulation and ballast protect the membrane. A surface coating can be applied to the roofs surface to help reduce UV effects and lower the buildings heating and cooling costs.
Pros and Cons of Built-Up Roofing
Built-up roofs tend to provide excellent waterproofing and ultra-violet protection. They’re low- maintenance and this means low life cost maintenance. They last longer and stand up better to weather inclemency.
But the process has some drawbacks as well. Installation is slower and with the exception of cold built-up, there can be hazard fumes and vapors involved when it’s being installed. Overall, installation costs are higher and some types of this roofing can be susceptible to wind and water damage.
Built-up roofs can become damaged as time goes by, and proper maintenance should be given to restore these areas.
Proper Installation and Maintenance are Critical
Regardless of the roofing system you choose, proper installation and regular maintenance (including regular inspections) is a must. When searching for a roofing contractor, make sure the company you hire is experienced and trained to install and maintain a Built-Up roofing system. Using a qualified roof consultant can significantly help with the process and help eliminate problems. Contact SMC Group for more information at (416) 731-7737