Atlanta Zoning | ADUs

Atlanta ADU Rules 2026: Where You Can Build a Second Home Behind the House

An accessory dwelling unit (ADU) is a small second home on the same lot as a house. In the City of Atlanta the rule has three limits. The ADU must be detached, it may have at most 750 square feet, and among the R districts it is listed in R-4, R-4A and R-5 only. The district rules date from 2017 and 2019. This page reads every rule from the City Code as updated September 24, 2026, and marks proposed changes as proposed.

What Atlanta Calls an ADU

The definitions chapter of the Zoning Ordinance sets the term. An accessory dwelling is "a detached dwelling unit meeting the height requirement of section 16-28.004 and having a floor area of 750 square feet or less on the same lot as a primary dwelling." The definition adds that ADUs are "distinct dwelling units" with "independent kitchen facilities."

Three things follow from that sentence. First, the unit is separate from the main house, so an apartment in a basement or an attached wing falls outside the definition. Second, the size cap of 750 square feet is part of the definition itself. Third, the unit has its own kitchen, which separates it from a guest house. The code defines a guest house as "a lodging unit for temporary guests in an accessory building" and says "no such lodging unit shall contain independent kitchen facilities."

The general rule for accessory buildings says the same thing. Section 16-28.004 says "use of accessory buildings as dwellings or lodgings is prohibited" unless the code allows it. The ADU lines in R-4, R-4A and R-5 are where the code allows it.

Every ADU Rule in One Table

Source: Atlanta Zoning Ordinance, code as updated September 24, 2026, sections linked in the last column.

Where ADUs Are Allowed

Three R districts list ADUs as an accessory use: R-4, R-4A and R-5. The wording is the same in each: "Accessory dwelling units, where the total number of dwelling units on any parcel, including the accessory dwelling unit, does not exceed two." The history notes show when each line was added. R-5 was first, by Ord. No. 2017-19 on May 1, 2017. R-4 and R-4A followed by Ord. No. 2019-09 on January 31, 2019.

R-1, R-2, R-2A, R-2B, R-3, R-3A and R-4B do not list ADUs. The cap of two homes also matters in R-5. An R-5 lot that already holds a duplex has two homes, so it cannot add an ADU.

A Department of City Planning page states that "Detached ADUs are currently allowed in R4, R4A, R5, and several of the city's SPIs and historic districts." SPI means Special Public Interest district. VanPlex did not read the ADU rules of each SPI and historic district, so check the chapter for your district if your lot is in one. The lot eligibility page shows how to look up the district.

Size, Height and the 30 Percent Rule

Two size limits apply together. The definition caps the ADU at 750 square feet. Section 16-28.004(3) then says accessory buildings in R-1 through R-5 "shall not contain a total floor area greater than 30 percent of the main structure." For that count, "all gross floor area of the accessory building shall be included whether or not it is conditioned or habitable." A garage under the ADU counts.

The ADU is held to the smaller of the two numbers. The table shows the arithmetic: 30 percent of the main house, compared with 750 square feet.

Worked examples by VanPlex from Sec. 16-28.004(3) and Sec. 16-29.001(10). Formula: the lesser of 750 sq ft or 0.30 times the floor area of the main house. A garage or storage room in the same building counts toward the 30 percent.

Height is limited to 20 feet, and accessory buildings may cover at most 25 percent of the area of the rear yard. In R-5 the ADU's floor area also counts toward the lot's floor area ratio of 0.50 for a house with an ADU. Floor area ratio is the floor area of the buildings divided by the area of the lot.

Placement, Yards and Timing

Accessory structures "shall be placed to the side or rear of the main structure within the buildable area of the lot so as not to project beyond the front of the main structure." In R-5 the code gives the ADU smaller yards than the house: a minimum of 4 feet at the side and 4 feet at the rear. A yard is the required open distance between a building and the lot line.

The order of construction is fixed. Section 16-28.004(2) allows an accessory building to be built at the same time as the main house or after it, and says "no accessory building shall be used or occupied until the principal building is completed and in use." You cannot build and rent the ADU first and add the house later.

In R-5 the ADU must also stay on the same lot as the house. Section 16-07.007 says "Accessory dwelling units may not be subdivided from their lot."

Parking

The parking sections of R-4 and R-4A each say "Accessory dwelling units: No parking required." The R-5 parking section, 16-07.010, has the same line, added by Ord. No. 2019-09 on January 31, 2019.

R-5 has one more line to read. Its list of special exceptions in Section 16-07.005(3) includes "Accessory dwelling units without off-street parking on parcels without a curb-cut or parcels without off-street parking." A special exception is an approval the Board of Zoning Adjustment grants at a public hearing. The two R-5 lines sit in the same chapter, so if your R-5 lot has no curb cut or no parking at all, ask the Department of City Planning in writing which line it applies before you design the site.

Renting an ADU

The lines that allow ADUs set one condition, the two-home total, and state no rule about who lives in either home. Short stays are treated differently. The definition of a short-term rental in Section 16-29.001(88) says: "An accessory dwelling unit may be used as short-term rental provided that the primary property owner resides onsite."

Atlanta's Short Term Rental Ordinance (Ord. No. 2021-14, March 24, 2021) sets the rest. A short-term rental is a stay "not to exceed 30 consecutive days." A license is required. An owner or long-term tenant may license "their primary residence and one additional dwelling unit." The application fee is $150 and is not refundable, and the license is renewed each year. Occupancy "is limited to two adults per bedroom," and the applicant must send notice by certified mail to each adjacent property. The R-4 and R-5 chapters also state that using a building as a party house "is expressly prohibited."

Site Rules and Loans That Affect an ADU

An ADU is new construction, so the site rules for new buildings apply to it. Atlanta's stormwater rules apply when a project creates 500 square feet or more of impervious surface, meaning roofs and paving that water cannot pass through. Removing a regulated tree, which is any tree other than a pine with a trunk of 6 inches or more, needs a permit from the City Arborist. The trees and stormwater page explains both.

Lenders have their own definitions. Fannie Mae's Selling Guide says "Only one ADU is permitted on the parcel of the primary one-unit dwelling" and "ADUs are not permitted with a two- to four-unit dwelling." Its rental income section lets a lender count rent from a one-unit ADU with a one-unit primary residence. FHA's handbook counts a property with two homes plus one ADU, or three homes plus one ADU, as a three- to four-unit property. The financing page covers these rules.

Proposed Changes That Have Not Been Adopted

Two sets of proposed changes exist. Neither is in the code.

The City planning proposal. The Department of City Planning page describes a proposal to allow attached ADUs (up to 50 percent of the main house or 1,000 square feet), raise the detached ADU height from 20 to 24 feet, raise the size from 750 to 1,000 square feet, add R-4B, and allow three homes in R-5. The page says R-1 to R-3 were left out after resident feedback, and that those districts hold 17 percent of Atlanta's one- and two-family lots by the City's own count. The page has no date. The code as updated September 24, 2026 still reads 750 square feet, detached, 20 feet, in R-4, R-4A and R-5, with two homes in total. The same page gives the City's own count: "At least 2,418 2 and 3 family housing units already exist today in single-family zoned neighborhoods."

ATL Zoning 2.0. The proposed zoning rewrite, ordinance 26-O-1508, was held in the City Council's Zoning Committee on September 14 and September 28, 2026. Its Draft V2, dated December 19, 2025, proposes that "accessory dwelling units may be attached or detached from the principal dwelling unit" and that "the total floor area of each accessory dwelling unit is limited to 850 square feet." The number of ADUs would depend on a use district:

Proposed. Source: ATL Zoning 2.0 Draft V2, Chapter 4: Use Districts, Use Table 1. R1 to R5 in this table are the draft's use districts. VanPlex has not confirmed how they line up with today's R-1 to R-5 zoning districts.

The draft also says an ADU is not allowed on a lot that already holds more homes than its district permits. Plan to the current code until Council votes. The ATL Zoning 2.0 page tracks the status.

Georgia Has No Statewide ADU Law

Each Georgia city and county writes its own ADU rule. The Governor's lists of signed bills for 2025 and 2026 contain no statewide ADU law. House Bill 1166, an ADU bill from the 2026 session, is absent from the 2026 list. Rules differ across the metro area as a result. Decatur allows one ADU of 300 to 800 square feet and requires the owner to live on the lot at least eight months a year. Unincorporated DeKalb County allows one ADU of up to 900 square feet on lots of 10,000 square feet or more. The metro page compares them.

Where to Go Next

Related on VanPlex: the Atlanta multiplex guide overview, ADUs in Texas and the missing middle guide.

Frequently Asked Questions

Official sources (checked October 2026)