Hartford, CT Accessory Structures: ADU Permits (2026)

An ADU project in Hartford navigates three layers. First, the City of Hartford Zoning Regulations (substantially rewritten in 2016 to form-based and use-based hybrid standards under Article II zones and Article IV use standards) treat most of the city's residential fabric as N1, N2, N3, N4, or N5 neighborhood districts, with two-family and three-family uses already permitted by-right in most N3 through N5 neighborhoods. An accessory dwelling unit is treated as an accessory use to the principal dwelling, subject to lot, setback, and parking standards in Article III (Dimensional Standards) and Article V (Parking, Loading, and Driveways). The Planning Division within the Department of Development Services administers zoning review and the Zoning Board of Appeals (Article VII) hears variances. Second, Connecticut Public Act 21-29 (2021), codified principally at CGS Section 8-1c and amending Section 8-2, requires every Connecticut zoning commission to allow ADUs as-of-right on lots with single-family dwellings, with state default standards (one ADU per lot, no separate sale, owner-occupancy not required by state law) unless the municipality opted out by a two-thirds vote of its legislative body by January 1, 2023. Hartford did not opt out, so PA 21-29 supplies the floor for ADU permission. Third, the Connecticut State Building Code (adopting the 2021 IBC and 2021 IRC with state amendments under CGS Section 29-252) and the Connecticut State Fire Safety Code (CGS Section 29-291, adopting the IFC) govern construction. Permits issue through the City of Hartford Department of Development Services / Licenses and Inspections (building, electrical, plumbing, mechanical). MDC (Metropolitan District Commission) handles water and sewer connections.