Gwinnett County, GA Accessory Structures: ADU Rules (2026)

10 sets both a location rule and a checklist of standards for detached accessory dwellings in unincorporated Gwinnett County. The unit must sit in the rear yard, with side and rear setbacks scaled to the base district: 20 feet side and 40 feet rear in RA-200 and R-LL, 10 feet side and 20 feet rear in R-100, 10 feet side and 15 feet rear in R-75, R-60, R-SR and TND, and 5 feet side and 10 feet rear in R-IF. Before anyone can occupy the unit, the owner of the principal dwelling has to apply for a Certificate of Occupancy specifically for the accessory dwelling and pay the fee the Board of Commissioners sets, and the Director arranges an inspection to certify the standards are met.

Those standards limit the project to one accessory dwelling per primary home, require the primary dwelling to be owner-occupied, cap the accessory unit at 50% of the principal residence's heated floor area, and require it to match the principal home's exterior style, materials, roof type, windows, color and trim if it's a separate building. The unit itself needs a full kitchen and at least one full bathroom, cannot exceed the principal dwelling's height if detached, gets excluded from the household's occupancy count under the UDO's definition of family, and needs its own paved off-street parking space plus a separate electrical meter, main disconnect, backflow preventer and shut-off valve on the water line.