{"data":{"id":"us-nyc/n.y.c.-admin.-code-bc-u203","jurisdiction":"us-nyc","citation":"N.Y.C. Admin. Code § BC U203","heading":"Section BC U203: ADU Separated by a Fire Wall from a Two-Family Primary Dwelling","body":"U203.1 Scope.\n\nAn ADU separated from the primary two-family dwelling by a fire wall that is constructed of concrete or masonry in accordance with Section 706 shall be constructed in accordance with all applicable requirements of a Group R-3 occupancy of this code, except as provided by in Section U103 and Sections U203.2 through U203.7.\n\nU203.1.1 Occupancy classification.\n\nWhere the ADU is separated from the primary two-family dwelling by a fire wall, both the ADU and the primary dwelling unit shall be classified as Group R-3 occupancy and shall comply with all applicable requirements of Group R-3 occupancy in this code.\n\nU203.2 Subgrade space limitation.\n\nThe ADU shall be located above the grade plane. The finished ground level of an under-floor space below the story above the grade plane shall be level with or higher than the outside finished ground level on at least 1 side.\n\nU203.3 Separate building required.\n\nThe ADU shall be constructed as a separate building from the primary dwelling. Both the ADU and the primary dwelling shall provide:\n\n1. All vertical circulation and exit systems required by this code without entering the other building.\n\n2. All fire protection systems required by this code without reliance on the other building. A shared water supply in accordance with Section U103.5.4 shall be permitted.\n\nU203.3.1 Construction class.\n\nThe construction class of an attached ADU shall not be lower than the primary dwelling.\n\nU203.4 Exterior walls.\n\nConstruction, projections, openings and penetration of exterior walls of an ADU shall comply with Sections 602 and 705.\n\nU203.5 Maximum building height.\n\nThe maximum building height of the ADU shall be determined in accordance with Section U103.8.\n\nU203.6 Type V construction in fire districts.\n\nNotwithstanding Section D105.1, an ADU completely or partially located inside the fire districts, as established in Section D101.2, is permitted to be constructed as Type V in accordance with Section U103.8.\n\nU203.7 Flood mitigation.\n\nThe department may promulgate rules relating to requirements for flood mitigation applicable to an ADU in the coastal flood risk area or 10-year rainfall flood risk area.\n\n(L.L. 2024/127, 12/18/2024, eff. 6/16/2025)","path":["New York City Administrative Code","Title 28","Chapter 7: New York City Building Code"],"source_url":"https://files.amlegal.com/pdffiles/NewYorkCity/Admin/XML.zip","current_through":"Local Law 2026/135 (enacted August 31, 2026)","vintage":"","retrieved_at":"2026-09-06T02:48:57Z","sha256":"4024882eea6af370676e400ee532e24f116d0b88afd2ed49106a6da4bf7207c1","source_id":"us-nyc","stale":false,"prev":"us-nyc/n.y.c.-admin.-code-bc-u202","next":"us-nyc/n.y.c.-admin.-code-bc-u204"},"notice":"GroundRules: Original legal text. Not legal advice."}