Is Drywall a WUI-Approved Product? Find Out Today

Learn why drywall is not WUI approved alone but as part of tested fire-rated assemblies for compliance.

By Brooke Fishel, Director of Stewardship and External Affairs, Gypsum Association

A cover of the IWUIC manual — International Code Council

Question: I'm designing a project in a wildfire-prone area. Is drywall considered a WUI-approved product, or does it have to be part of a tested assembly?

Answer: This is a common question among architects, contractors, and code officials working on projects subject to the International Wildland-Urban Interface Code (IWUIC or WUI). The short answer is that gypsum panels are not "WUI-approved" products by themselves. Rather, they are components of tested assemblies that may be used to satisfy WUI code requirements.

Part of the confusion stems from terminology. The IWUIC uses terms such as fire-resistance-rated construction, ignition-resistant construction, and noncombustible materials. Although these terms may sound similar, they have distinct meanings. As explained in the Gypsum Association article, Fire-Related Terms in the IWUIC: Clearing Up Definition Confusion, understanding the difference between these terms is important because they describe the performance of an assembly or system, not the attributes of an individual product.

The IWUIC and similar state and local regulations establish requirements intended to reduce a building's vulnerability to wildfire. Compliance is based on the performance of the complete assembly rather than any single material.

For example, a one-hour exterior wall assembly may include 5/8-inch type X gypsum board or gypsum sheathing, along with framing, insulation, fasteners, and exterior cladding. These components work together as a system to achieve the required level of fire resistance. Substituting or omitting components could affect the assembly's performance and its ability to comply with applicable code requirements.

This distinction is similar to another common misconception in the industry: there is no such thing as "one-hour drywall." Fire-resistance ratings are assigned to complete assemblies tested in accordance with ASTM E119, not to individual gypsum panels. Likewise, no gypsum panel by itself can be considered "WUI approved."

Gypsum panels contribute to the fire performance of these assemblies because they are noncombustible and contain chemically combined water that is released when exposed to heat. This process helps slow heat transfer and delays the spread of fire. As a result, gypsum panels and gypsum sheathing are frequently incorporated into fire-resistance-rated wall and ceiling assemblies used in WUI construction.

When designing or constructing in a WUI area, architects and contractors should focus on selecting complete, tested assemblies that satisfy the requirements adopted by the local jurisdiction. Resources such as GA-600, Fire Resistance and Sound Control Design Manual, along with a clear understanding of IWUIC terminology, can help ensure that code requirements are properly interpreted and applied.