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MBMA Announces New UL Design Number W447 Interior Fire-Rated Wall Assembly Listing

Cleveland, OH -The Metal Building Manufacturers Association (MBMA) announces a new fire-rated wall assembly listing, UL Design No. W447. The new fire resistance-rated, non load-bearing metal building interior wall assembly will be acceptable where one or two-hour ratings are required by building codes.

 Vincent E. Sagan

“UL W447 is a result of applying previous testing for an exterior wall assembly to a new interior wall assembly. This innovation provides required fire protection more efficiently in metal building systems,” said Vincent E. Sagan, PE, Senior Staff Engineer at MBMA.

MBMA submitted the design proposal to UL, a global independent safety science company that certifies materials, systems and assemblies used for structural, fire resistance, and safety purposes. UL performed an engineering study based on UL V421 and subsequently generated UL W447, which is now listed in the UL Fire Resistance Directory.

Dan Walker

“As time goes on, MBMA continues to improve upon its fire-rated assemblies to make them more metal building friendly. It’s a natural progression for us to continue to develop new systems using metal building components and fewer outsourced materials. This new design will help designers and contractors to meet building codes, which helps grow the market for metal buildings,” said Dan Walker, PE, Associate General Manager of MBMA.

The UL fire-resistance design listings enable higher occupancy for commercial, institutional, and governmental uses and can increase allowable floor area. The new UL W447 design consists of horizontal girts clad with furring channels and gypsum board on both sides of the wall. The girts are connected to columns or adjacent wall framing, and insulation can be added in the wall cavities.

Eighteen existing UL-rated assemblies for metal building applications are available on the Fire Protection page of the MBMA website, An additional resource is MBMA’s “Fire Resistance Design Guide for Metal Building Systems,” available at

The MBMA is comprised of metal building system manufacturers and their suppliers who fabricate or manufacture materials for its member companies, and also architecture and engineering firms and service providers. The association is dedicated to educating industry professionals about best practices for metal building design and construction.

For additional questions or inquiries about fire-resistance ratings in metal buildings, please contact Vincent Sagan at

About The Metal Building Manufacturers Association

mbma-logoFounded in 1956, MBMA serves manufacturers and suppliers as it works to promote the metal building systems industry. Its membership supplies high-quality buildings for use in commercial, retail, office, industrial, institutional and other end-uses. The association provides a wealth of information on its website for anyone who works with or is interested in metal building systems. It includes technical materials and design guides. For more information, visit

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