New Haven, CT Accessory Structures: ADU Permits (2026)

An ADU project in New Haven sits at the intersection of city zoning, state statute, and state building/fire code. First, the New Haven Zoning Ordinance (eCode360 NE0810) governs use, dimensional, and parking standards across the city's residential districts (RS-1, RS-2, RM-1, RM-2, and the form-based BD districts in the downtown area). Two- and three-family use is permitted by-right in most RM districts, and ADUs are reviewed as accessory uses to a principal dwelling, subject to setback, height, and lot-coverage standards. The City Plan Department administers zoning review and the Board of Zoning Appeals hears variances under CGS Section 8-6. Second, Connecticut Public Act 21-29 (signed June 10, 2021), principally codified at CGS Section 8-1c and amending Section 8-2, requires every Connecticut zoning commission to allow one ADU as-of-right on each lot with a single-family dwelling, with state default standards (size, setbacks, height, parking) that the local commission may refine through objective criteria but may not restrict with owner-occupancy or family-relationship preconditions. The opt-out window closed January 1, 2023; New Haven did not opt out, consistent with its broader pro-housing zoning reforms. Third, the Connecticut State Building Code (CGS Section 29-252, adopting the 2021 IBC and 2021 IRC with state amendments) and the Connecticut State Fire Safety Code (CGS Section 29-291, adopting the IFC) govern construction. Permits issue through the New Haven Building Department (building, electrical, plumbing, mechanical), with the Regional Water Authority (RWA) handling water service and the Greater New Haven Water Pollution Control Authority (GNHWPCA) handling sewer connections.