Hot-Applied Asphalt Performs Well in Severe Weather
Fully Adhered Built Up Roofs Withstand Hurricane Force Winds with Minor Damage
[Washington, DC] – According to the Quality Commercial Asphalt Roofing Council (QARC) of the Asphalt Roofing Manufacturers Association (ARMA), hot-applied BUR systems offer better protection in severe weather than synthetic roof membranes.
“A BUR system has substantially greater mass than a single-ply system,” says Reed Hitchcock, Executive Director of ARMA. “A four-ply BUR system provides about 280 mils of waterproofing thickness whereas most single-ply systems average 60 mils or less. The multiple layers of a BUR system result in a thick, heavy membrane that provides good protection against wind-uplift and penetration by wind-blown objects.”
In addition, when asphalt is applied directly to a structural concrete roof deck or a hot-applied asphalt roof system is applied to an insulated roof deck, it is considered to be a fully adhered system. An important benefit of fully adhered systems is they distribute typical building stresses (such as wind load, vibration and flexing) over an entire roof membrane.
“A properly installed, fully adhered BUR system has an excellent chance of surviving hurricane force winds intact,” says Hitchcock. “This claim is well-supported by the reports on wind-related damage from in the aftermath of severe storms such as Hurricanes Ivan and Charley.”
According to Hitchcock, single-ply systems that are not fully adhered have fasteners designed to hold a roof membrane in place. But events such as high winds can produce stress concentrations, or point loading, strong enough to compromise the integrity of the roof or tear apart the roof membrane. Appropriate fasteners spaced closely together are used successfully in many roof systems. Liquid asphalt also adheres well when applied directly to certain surfaces, eliminating the need for fasteners. For example, asphalt can be applied directly to a structural concrete roof deck after priming. It often can be hot-mopped to thermal insulations though manufacturers' recommendations should be followed. Of course, liquid asphalt adheres well to the felts and base sheets used in the construction of a multiple-ply roof system.
“Reports from heavily storm-damaged areas support the claim that BUR systems perform well in extreme weather,” says Hitchcock. For example, the Roofing Industry Committee on Weather Issues (RICOWI) Inc. reported on investigations of wind-related damage to low-slope roofs from Hurricanes Charley and Ivan. According to Hitchcock, case studies in the report include many examples of BUR systems withstanding severe weather. Wind speeds from Hurricane Charley, in particular, were in the 120-mph to 150-mph range, yet in many cases BUR systems sustained only minor damage. In some cases, metal flashings were damaged but the BUR membranes remained intact. (The complete report, titled "Hurricanes Charley and Ivan Wind Investigation Report, March 2006," is available on RICOWI's Web site, www.ricowi.com.)
For additional information concerning ARMA or QARC, their programming and activities, contact ARMA at (202) 207-0917; fax (202) 223-9741; or visit the ARMA web site at www.asphaltroofing.org or www.qualityasphaltroofing.org.
About the Asphalt Roofing Manufacturers Association
The Asphalt Roofing Manufacturers Association (ARMA) is the North American trade association representing the manufacturers and suppliers of bituminous-based residential and commercial fiberglass and organic asphalt shingle roofing products, roll roofing, built-up (BUR) roofing systems, and modified bitumen roofing systems.
The Quality Asphalt Roofing Council (QARC) is an initiative created to support and promote built-up and modified bitumen roof systems under the auspices of the Asphalt Roofing Manufacturers Association. The council is composed of roll goods producers, asphalt suppliers, equipment manufacturers, packaging suppliers and others.
-- # --