Flat Roofing
Flat roofs--or Built-Up Roofs (BUR)--are the most economical choice. However, flat roofs may not be appropriate for all houses.
Flat roofs are most popular in low-rain areas, and the existing roof must have a low pitch or slope, or already be flat. Also, proper maintenance of a flat roof is of the utmost importance; homeowners should check their flat roofs twice a year as they can collect debris.
The process of installing a flat roof is different from that of other roofing systems. A built-up roof is just what it sounds like--a roof that is literally built layer by layer. Those layers are composed of roofing felt alternated with different materials such as coal tar pitch, asphalt, cold application adhesive and modified asphalt. BURs are also known as "tar and gravel" roofs since they're finished off with a layer of gravel, crushed rock or other mineral substance in order to minimize sun damage.
A modified bitumen roof (MBR) is another type of flat roof, and is made from fiberglass-based asphalt sheeting, which is applied in layers with mopped-on hot bitumen between each one.
Typical life expectancy for a BUR ranges from 15 to 25 years, depending on the ply of the roof. 4-ply is the most common, with an average life expectancy of 20 years.
Quick facts about flat roofing:
- Maintenance is key: neglect can cause leakage and water accumulation
- All flat roofs need an excellent drainage system
- Gravel reflects UV radiation
- Gravel also helps rainwater spread across the roof, increasing surface area for faster evaporation