Posted in Building Codes
Along the coast and in hurricane zones, homebuilders have unique concerns about the quality of their building materials, such as the ability of fasteners to stay in place in winds up to 150 miles per hour. These concerns add a new dimension to the age-old debate over which is better, plywood or OSB. The city of Galveston, Texas, recently jumped into the debate, bringing the matter to an official vote before the city council.
The Galveston City Council wanted to know which material was best for roof decking and exterior wall sheathing. To get straight answers from an unbiased source, the council turned to APA–The Engineered Wood Association, which represents both manufacturers of plywood and manufacturers of OSB products.
APA engineer Bruce Cordova took the bulk of the questions from the council members and Galveston Mayor Joe Jaworski during a 30-minute Q&A session. According to Cordova, who was well armed with technical data to back APA’s recommendations, “when used as intended, the two products meet the same building code requirements and can be used interchangeably” in roof decking and exterior wall sheathing. It’s a fact that holds true even in hurricane-prone areas like Galveston, which sits on an island along the Texas coast in the Gulf of Mexico.
“Both products, although different in composition and appearance, are manufactured according to a set of standards that have similar performance requirements,” said Cordova. “Those standards include structural performance tests under wet and dry conditions. ”
The APA acknowledges that OSB can have greater thickness swelling than plywood when subjected to prolonged water exposure, but extensive APA testing shows that this swelling does not affect panel structural performance in these applications once panels are able to dry out.
Additional independent testing by Western Roofing shows that both OSB and plywood meet the same standards for nail withdrawal strength at 60 psf and 90 psf—even when soaked under running water for 24 hours, dried, and then soaked under running water for another 24 hours.
The Galveston City Council was not only concerned about performance but also environmental sustainability. Rick Crawford from LP Building Products was able to provide the mayor and the council members with an explanation of the environmental advantages of OSB.
Given the facts, the Galveston City Council voted unanimously to approve the use of OSB for roof decking and exterior wall sheathing for new home construction.
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