Can I turn my basement into an ADU in Atlanta?

Not as a separate legal unit in the City of Atlanta, as of October 2026. City Planning says attached ADUs, which include basement conversions, are not currently allowed. You can finish a basement as part of the main house, and a city proposal would allow attached ADUs if adopted. In Decatur, a lower-level ADU is allowed under the city's ADU rules.

What counts as an attached ADU?

A second dwelling inside or joined to the main house, with its own kitchen and living space. A finished basement with a bedroom, bathroom and family room, but no separate kitchen and still connected to the house, is usually just more living space for the main home, not a second unit.

What would the city's proposal change?

City Planning's published proposal would allow attached ADUs up to 50% of the main dwelling or 1,000 sq ft, in the districts that allow ADUs. It is a proposed policy, not adopted law, as of October 2026. Atlanta's draft zoning rewrite, held for revisions in September 2026, could also change the picture.

Where nearby can a basement be an ADU?

• Decatur. The city's ADU page names the lower level of the house as an example of an attached ADU. Limits: 800 sq ft, 40% of the main house, two bedrooms, owner on site at least eight months a year. See Decatur.
• Sandy Springs. The development code, as published, allows a guest house attached to the main home. See Sandy Springs.
• Marietta. The code's ADU definition includes attached units to the rear of the house. We confirm the use rules with the city.

What does a basement need to become a legal unit?

It depends on the basement. Where a code allows a lower-level unit, the building code typically looks for:

• enough ceiling height in living areas
• an emergency escape opening in each sleeping room, such as an egress window or door
• fire separation between the two dwellings
• a separate entrance
• drainage and moisture control, often with a sump or ejector pump
• its own heating and cooling, or a properly zoned system

Daylight basements on sloped lots, common across metro Atlanta, often meet the entrance and egress requirements more easily than fully underground ones.

What if I just want a suite for family?

A finished basement suite without a separate kitchen can usually be permitted as part of the house. It will not be a rentable second unit, but it can give a parent or adult child private space now. If Atlanta adopts attached ADUs later, a well-planned suite may be easier to convert. See attached ADUs and in-law suites.