Built-up Roofing (BUR), as any expert roofing contractor will say, has been around for a long, long time and has an excellent record of long-term performance for property owners. This long-term performance is based on a few simple rules that most roof consultants and designers know but may overlook on occasion.

While these rules apply to built-up roofing, most low-slope systems are covered by several of them. This article reviews these rules and why they should be taken into account.

ASTM D312 Type III and Type IV

While ASTM D312 Type III and Type IV represent approximately 95% of the hot asphalt sold for use in today’s roofing industry and are acceptable for use in most of the country’s geographic areas, this rule still needs to be stated.

Generally speaking, the specifications and recommendations of manufacturers for commercial or residential roof installation state that a built-up roof with approximately 25 pounds is being constructed. This quantity of asphalt for each installed ply is equivalent to a cross-section about the thickness of a dime.

Expansion and Contraction

Built-up roofing systems also have sufficient strength to withstand normal expansion and contraction forces exerted on a roof; however, they typically have low capacity to accommodate excessive movement of buildings or substrates.

It seems elementary, but the roofs are not supposed to pond water to avoid a residential or commercial roofing repair. There are, of course, exceptions to this, such as limiting the run-off of precipitation to help antiquated stormwater systems that cannot handle rainwater. With low-slope roofing applications, however, ponding water should generally be avoided.

Timberline Roofing & Contracting is the company to call if you need help with your roof in Minneapolis, MN, and in other surrounding areas. Give us a call today at (612) 263-9700.