Gwinnett County, GA Accessory Structures: ADU Owner Occupancy (2026)

10 of the Unified Development Ordinance, detached accessory dwellings in unincorporated Gwinnett County may only sit in a rear yard, with setbacks that scale to the base zoning district: 40 feet in RA-200 and R-LL, 20 feet in R-100, 15 feet in R-75, R-60, R-SR and TND, and 10 feet in R-IF. Before anyone occupies the ADU, the owner of the principal dwelling must apply for a separate Certificate of Occupancy and pay the fee set by the Board of Commissioners; the Director of Planning and Development then inspects the unit to confirm it meets the standards.

The core rule is owner-occupancy: the primary dwelling unit on the lot must be owner-occupied, not just the ADU. Only one accessory dwelling unit is allowed per primary dwelling unit, and it cannot exceed 50 percent of the principal residence's heated floor area. The ADU may be attached with its own entrance or fully detached, but a detached unit's height cannot exceed the principal dwelling's height, and its exterior style, materials, roof, doors and windows must match or be compatible with the main house. Every ADU must include a full kitchen and at least one full bathroom, at least one dedicated paved off-street parking space beyond what the primary home already provides, its own electrical meter and main disconnect, and a backflow preventer and shut-off valve on the water line.

Occupants of the ADU are not counted toward the primary dwelling's occupancy under the UDO's definition of family. These standards were adopted as part of the county's UDO rewrite, Ord. No. UDOA2023-00002, effective September 26, 2023.