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G:\BDP Policies\BDP 14 Shower-Bath Backing Material.docx Page 1 of 1 Community Development Department Building & Safety Division Policy No.: BDP 14 Original Effective Date: May 1, 1990 Revised Date: January 1, 2020 Initiated By: Vic Taugher, Building Official Approved By: Gregory A. Shreeve, Sr., Chief Building Official Subject: Backing Material in Shower and Bathtub Enclosures for All Occupancies Code References Sections R702.3.7 and R702.3.7.1 of the 2019 California Residential Code The code addresses the limitations of water-resistant gypsum backing board where in direct exposure to water or in areas subject to continuous high humidity. The City of Dublin has determined that water-resistant gypsum board is adversely affected by moisture and as such, does not allow direct glue-on-tile applications. Greenboard will only be allowed under solid panel wall covering fiberglass or marble) as joints occur only in the corners. The backing material to be used for all occupancies shall be cementitious material or gypsum board approved for this installation. The National Evaluation Service (NES) has provided evaluation reports on various products allowed for these uses. If a product evaluation report is not provided to the Building & Safety Division, the applicant shall provide the Division with a listing/testing report which shall be reviewed and approved by the Chief Building Official. Similar 2019 California Building Code sections which address limited installation methods are: Section 2509.2 - Base for tile. Regular gypsum wallboard is permitted under tile or wall panels in other walls and ceiling areas when installed in accordance with GA-216 or ASTM C 840. Section 2509.3 - Limitations. Water-resistant gypsum backing board shall not be used in the following locations: 1. Over a vapor retarder in shower or bathtub compartments. 2. Where there will be direct exposure to water or in areas subject to continuous high humidity. The Building & Safety Division has determined that greenboard is not a moisture-resistant material.