Lithonia

DeKalb County, GA (738,000 residents in suburban Atlanta) administers the DeKalb County Zoning Ordinance for unincorporated territory. The ordinance permits accessory dwelling units in specific residential districts subject to size, owner-occupancy, and setback conditions. Most of DeKalb is unincorporated (a notable contrast to Fulton); incorporated cities include Decatur, Avondale Estates, Brookhaven, Chamblee, Doraville, Dunwoody, Pine Lake, Stone Mountain, Stonecrest, Tucker, and parts of Atlanta. Each incorporated city sets its own rules.

• DeKalb County Zoning Ordinance

State-floor overlay: Georgia has not enacted statewide ADU preemption.

DeKalb County administers flood-hazard, and (where mapped) coastal, wildland-fire, historic, and airport overlays that shape ADU project feasibility. The most consistent overlay across the county is FEMA NFIP floodplain regulation; other overlays apply to specific geographies inside the county.

• FEMA NFIP Special Flood Hazard Areas in DeKalb County — A new ADU in a mapped SFHA must be elevated to or above the Base Flood Elevation; cost impact on the project is often material.
• Historic districts and individually-listed historic resources

DeKalb County issues building permits for parcels in unincorporated territory through its development services / planning department, with separate review tracks for zoning conformance, building-code compliance, on-site sewage where applicable, floodplain compliance, and addressing. Inside incorporated municipalities, city departments handle their own permits; the county's authority is geographically limited to unincorporated territory. An ADU permit application is typically processed as a residential building permit with a zoning verification step against the county's ordinance for the parcel's zoning district.