Can I substitute Fire-retardant-Treated Wood for Gypsum in a UL Design?

No. Fire-retardant-Treated Wood cannot be substituted for gypsum in any UL Design. Fire-retardant-Treated Wood may be added to a UL Design following the requirements for adding wood structural panels found in the UL BXUV Guide Information for Wood Structural Panels (General) and Wood Structural Panels in Wall Assemblies.