The National Frame Building Association (NFBA) has successfully tested a post-frame 3-hour fire wall system that can now be incorporated into a post-frame building without having to seek out expensive traditional non-wood framing systems.
Full-scale testing of a 3-hour post-frame fire wall in December 2011 by Underwriters Laboratories (UL), Northbrook, IL, showed for the first time that a wood-constructed assembly is a viable alternative to a traditional block wall system.
The post-frame building system is categorized as a Type 5 structure under the International Building Code (IBC). An hourly rated wall— rated as high as 3 hours—is often required to separate building areas or occupancy types to meet the IBC requirement for life safety.
For architects, builders, and engineers, that traditionally has meant using a rated 8-inch or 10-inch concrete block wall on a concrete foundation, but with this recent test exceeding hour-rating expectations, that may no longer be the case.
“The post-frame assembly nearly made 4 hours (3 hours and 47 minutes), thus obtaining UL’s 3.5-hour rating,” said Leo F. Shirek, co-chair of NFBA’s Technical and Research Committee and a member of its 3-Hour Post-Frame Fire Wall Subcommittee. “It’s quite a testament to the quality of post-frame construction.”
The test assembly was a post-frame structure with four layers of 2 x 6 laminations in the columns, spaced 8 feet apart with 2 x 4 girts 16 inches on center applied horizontally on each side. The frame was then sheathed with four staggered layers of 5/8 type X drywall on both sides. All joints were untapped.
Post-frame wall assembly is an extremely economical alternative, Shirek says. “We began testing work for this project in early 2011 knowing that, from an industry standpoint, we could create a wall that was much more cost-effective than a typical block wall, which costs $12−$15 per square foot. We felt that a post-frame fire wall with drywall could potentially halve that cost.”
Sherik notes that a post-frame fire wall is faster to erect than a stud-wall system, a light-gauge steel-stud wall system, and particularly block walls, which generally require an expensive foundation. “A post-frame wall can be built and incorporated into the natural flow of the building process, possibly saving as much as a couple of weeks in completion time.”
“We are optimistic that this test will be a building block for other approvals and possibly for other future tests that can benefit the industry,” Shirek says. Testing, which follows the requirements of the UL 263 (ASTM E119) standard of ASTM International [formerly known as the American Society for Testing and Materials], included a fire test and a stringent water-pressure test.