The short answer
In the City of Atlanta you can build one detached ADU of up to 750 square feet on a lot zoned R-4, R-4A or R-5, without a rezoning. It can be up to 20 feet tall, needs no extra parking, and must sit beside or behind the main house. Lots zoned R-1, R-2 and R-3 don't allow an ADU today.
| Rule | R-4 and R-4A | R-5 |
|---|---|---|
| ADU allowed by right? | Yes, one detached ADU | Yes, one ADU (two units total on the lot) |
| Maximum size | 750 sq ft, and accessory buildings are also limited to 30% of the main house's floor area | |
| Maximum height | 20 ft | |
| Side setback | 7 ft | 4 ft |
| Rear setback | 15 ft | 4 ft |
| Location on lot | Beside or behind the house, not in the front yard | |
| Lot coverage cap | 50% | 55% |
| Extra parking | None required | |
| Sell the ADU separately? | No, it stays on the same lot as the house | |
| Short-term rental | Only when the owner lives on the property and holds a city STR license | |
The 750 sq ft cap comes from the code's definition of an accessory dwelling unit. Accessory buildings in R-1 through R-5 are also capped at 30% of the main house's floor area, so a 2,000 sq ft house allows about 600 sq ft. Some older guides quote 1,000 sq ft and 24 ft; those numbers come from proposals that have not been adopted (see Zoning 2.0).
Which zoning districts allow ADUs
The city's ADU ordinance (Ord. 18-O-1581, in effect since January 31, 2019) allows ADUs as an accessory use in three single-family districts. Together they cover a large share of the city's residential land, including much of Kirkwood, East Atlanta, Grant Park, Ormewood Park, Reynoldstown, West End, Edgewood and Capitol View.
- R-5 (two-family residential): the most flexible. One ADU, as long as the lot has no more than two homes in total. 4 ft side and rear setbacks.
- R-4 and R-4A (single-family residential): one detached ADU with 7 ft side and 15 ft rear setbacks.
- R-1, R-2, R-2A, R-3 and R-4B: no ADU without a rezoning.
Some special public interest (SPI) and historic districts have their own rules, and historic districts add a design review. If your lot is in one, plan for extra time.
How to look up your lot
- Open the City of Atlanta Property Information map and search your street address.
- Note the zoning district (for example "R-4A") and whether the parcel sits in a historic or SPI district.
- Check the jurisdiction. Plenty of addresses that say "Atlanta" are in unincorporated DeKalb or Fulton County, Sandy Springs, Brookhaven or another city with its own code.
- Get a current boundary survey. Setbacks are measured from property lines, not fences.
Or send Christina your address and she'll do the first look for you.
Size, height and where it can go
Size. Up to 750 sq ft of floor area, and no more than 30% of the main house's floor area. The rear-yard footprint is also limited, and the whole lot must stay under its floor-area and lot-coverage caps (50% coverage in R-4 and R-4A, 55% in R-5).
Height. Accessory buildings top out at 20 ft. That leaves room for a one-story cottage with a vaulted ceiling, or a compact two-story design on a small footprint like the Oakland ADU pictured on our home page.
Setbacks. 4 ft from the side and rear lines in R-5; 7 ft side and 15 ft rear in R-4 and R-4A. Corner lots also have to respect the side-street yard, and on alley lots the rear setback can be measured differently. A variance from the Board of Zoning Adjustment can reduce a setback, but it takes time and is never guaranteed.
Location. The ADU goes beside or behind the house, not in the front yard.
Parking, utilities and ownership
The city requires no additional off-street parking for an ADU in R-4, R-4A or R-5. In R-5, an ADU on a lot with no curb cut or off-street parking at all is handled as a special exception, so ask the Office of Zoning if that's your situation.
The ADU can't be subdivided or sold apart from the main house. Owner occupancy is not required for a long-term rental, but it is for a short-term rental (see renting your ADU).
Utilities aren't a zoning rule, but they often decide the budget. Distance to the sewer line, whether a pump is needed, and whether the power service needs an upgrade are worth checking before design starts.
Attached, basement and garage apartments
The city's ADU rules cover detached units. An apartment in a basement or attached to the house is treated as a second dwelling unit, which is only allowed where a two-family use is allowed (R-5). There is no "junior ADU" category in Atlanta.
That means a basement apartment in an R-4 neighborhood is usually a remodel, not a rentable second unit. A detached garage, on the other hand, can sometimes become an ADU if it meets the ADU size, height and setback rules. Our garage and basement conversion guide covers both.
Outside the city limits
Decatur, DeKalb County, unincorporated Fulton County, Sandy Springs, Brookhaven, Roswell, Alpharetta, Marietta, Smyrna and Gwinnett each write their own accessory-dwelling rules, and they differ on size, owner occupancy and whether attached units are allowed. Some suburban codes are more generous than the city's for basement and attached suites. Tell us your address and we'll start from the right code.