Vapor Retarder over Water-Resistant Gypsum Board – GA-230-2025 (PDF Download)
Water-resistant gypsum board (as defined in ASTM C1396, Standard Specification for Gypsum Board) is used as a base for the application of ceramic or plastic wall tile or plastic finished wall panels for use in areas with elevated levels of humidity or incidental water exposure (See Notes 1 and 2). Water-resistant gypsum board shall not be used where there will be direct exposure to water or continuous high humidity conditions. Such areas include but are not limited to saunas, steam rooms, gang shower rooms, and indoor pools.