Case Study: OSB Approved For Use in Hurricane Zones

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 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.

Objectives

In particular, the Galveston City Council wanted to know which material was best for roof decking and exterior wall sheathing in a hurricane zone. Additionally, council members were concerned about the ecological impact of the manufacturing of each product. To get straight answers from an unbiased source, the council turned to APA–The Engineered Wood Association, which represents manufacturers on both sides of the debate—both plywood and OSB.

Implementation

The city council and Galveston Mayor Joe Jaworski hosted a 30-minute Q&A session, with senior APA engineer Bruce Cordova taking the bulk of the questions. Well armed with technical data to back his expert opinion, Cordova informed the council that “when used as intended, the two products are interchangeable” in roof decking and exterior wall sheathing. According to Cordova, 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 fastener withdrawal and structural performance tests under wet and dry conditions. OSB products meet the same performance requirements of roof decks and exterior sheathing as plywood when properly designed and installed.”

Although the APA acknowledges that OSB can have greater thickness swelling in wet conditions than plywood when exposed to prolonged moisture exposure, APA testing shows that this swelling does not affect panel structural performance in roof decking and exterior wall sheathing. Additional independent testing by Western Roofing shws 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, 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—including third party-certified forestry practices, the use of young trees that are quickly replenished, and a manufacturing process that uses 100% of the log.

Outcome

The Galveston City Council voted unanimously to approve the use of OSB for roof decking and exterior wall sheathing for new home construction. Homebuilders working in the area can freely choose between OSB and plywood based on their own personal preference, comfort level, availability, pricing, professional relationships, or other reasons. In the eyes of the city and its building codes, the two materials are interchangeable.


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Comments (2)


  1. Robert

    OSB may still be able hold nails after it get wet, but not it’s shape. When OSB gets wet it strtches out a little bit like plywood, but the difference comes when they dry. OSB doesn’t return to it’s original shape like plywood does. I have done this test myself and know it is true. Also, the amount of adhesives used to create OSB is far more than plywood. The glues or bonding agents r affect some people very sensitive to chemicals so I only use plywood for interior walls. This comparison or any comparison for indoor use was neglected, why?


  2. Engineered Wood

    Hi Robert, thanks for reading the article! In response to your comment, we wanted to let you know that OSB panels will expand slightly in length and width when they get wet, however OSB is not intended to stay wet and the panels will return back close to their original size after they dry to a typical in-service moisture content. LP does require 1/8″ spacing during installation to accommodate this expansion and contraction that may occur. Although indoor use is beyond the scope of this article it is important to note that all of LP’s Engineered Wood products use only low emitting, safe resins.

    If you have any further questions, please contact LP at 1-888-820-0325. Thanks!