Metro | Decatur, DeKalb and Beyond
Decatur, DeKalb and Metro Atlanta: Duplex, Fourplex and ADU Rules
The rules change at every city limit in metro Atlanta. Each city has its own code, and a county's zoning code covers the land outside its cities, which is called the unincorporated area. Georgia has no statewide law on accessory dwelling units (ADUs) or small multi-unit buildings, so the local code decides what may be built. This page covers six places: the City of Decatur, unincorporated DeKalb County, Sandy Springs, the City of South Fulton, unincorporated Gwinnett County and, for comparison, the City of Atlanta. Each rule below was read from the adopted code.
Metro Atlanta rules in six facts
- Decatur's ordinance O-23-Z-01, dated February 6, 2023 in the code's history notes, added Duplex and Walk Up Flat as allowed building types in the single-family districts R-85, R-60, R-50 and RS-17. Source: Decatur Unified Development Ordinance, Article 3
- A Decatur walk up flat is "a building type designed to accommodate three to four principal dwelling units" on a single lot. Source: Decatur Unified Development Ordinance, Sec. 2.2.3.G
- Decatur allows one accessory dwelling unit per lot, between 300 and 800 square feet and no more than 40 percent of the floor area of the principal dwelling. The owner must live on the property at least eight months of each year. Source: Decatur Unified Development Ordinance, Article 6
- Unincorporated DeKalb County permits one accessory dwelling unit by right on a lot of at least 10,000 square feet. The unit may not exceed 900 square feet of heated floor area or 24 feet in height. Source: DeKalb County Code, Sec. 4.2.3
- In 2025, Decatur, Sandy Springs (11 months reported), South Fulton, Marietta and Brookhaven each reported zero permits for two-unit buildings and zero for three-to-four-unit buildings. The City of Atlanta reported 78 and 64. Source: US Census Bureau, Building Permits Survey 2025
- Georgia signed no statewide law on accessory dwelling units or lot sizes in 2025 or 2026, so each city and county code decides what may be built. Source: Governor of Georgia, signed legislation 2026
Six Places Compared
| Place | Two to four homes in one building | ADU or guest house | Must the owner live on site? |
|---|---|---|---|
| City of Atlanta | A duplex in R-5. Three or more homes need RG, R-LC or MR zoning. | Detached, 750 sq ft at most, in R-4, R-4A and R-5 only | The lines that allow ADUs in R-4, R-4A and R-5 state no owner-occupancy condition. Using the ADU as a short-term rental requires the primary owner to live on site. |
| City of Decatur | Duplex and walk up flat (3 to 4 homes) are limited uses in R-85, R-60, R-50 and RS-17, and permitted uses in RM-18, RM-22, RM-43 and PO. | 300 to 800 sq ft, at most 40% of the principal dwelling, at most two bedrooms, one per lot | Yes. The owner must live in the principal dwelling or the ADU at least eight months of each year. |
| DeKalb County (unincorporated) | Two-family and three-family dwellings are permitted in the RSM, MR and HR districts. They are not listed in R-60 and the larger-lot districts. | Attached, detached or inside the house. 900 sq ft of heated floor area and 24 ft tall at most, on a lot of at least 10,000 sq ft | Yes. The owner must live in one of the two homes and hold a homestead exemption. |
| City of Sandy Springs | The "Neighborhood Unit" standard allows up to 12 homes per building, and no more than 4 per building in RU districts. The districts that permit it were not read. | "Accessory Dwelling, Guest House": heated floor area under 1,500 sq ft, 2 stories at most, one per lot, attached or detached | Not stated in the standard that was read. |
| City of South Fulton | Not read. | One guest house per lot, 650 to 1,500 sq ft of heated floor area, or a "Tiny House" of 400 sq ft at most | The guest house is for relatives, guests or employees who work on the property, "without payment for rent." |
| Gwinnett County (unincorporated) | Duplex, triplex and fourplex dwellings are conditional uses in the R-IF and LRR districts. They are not listed in RA-200, R-LL, R-100, R-75 or R-60. | At most 50% of the heated floor area of the principal residence, one per primary dwelling, attached or detached | Yes. "The primary dwelling unit shall be owner-occupied." |
Sources: Atlanta Zoning Ordinance (code updated September 24, 2026); Decatur Unified Development Ordinance (code updated December 11, 2025); DeKalb County Code, Chapter 27 (updated September 2, 2026); Sandy Springs Development Code, Article 7 (updated February 11, 2026); City of South Fulton Zoning Ordinance, Article 3 (updated August 26, 2026); Gwinnett County Unified Development Ordinance, Chapter 210 (updated March 27, 2026). The update dates are the ones shown by the code publisher, Municode.
The table shows one clear pattern. Among the four codes whose use tables were read (Atlanta, Decatur, DeKalb County and Gwinnett County), Decatur is the only one that allows a three- or four-home building in its single-family districts. In the other three, a lot in a single-family district needs a rezoning before it can hold more than a house and, where the code allows one, an accessory unit.
A second pattern is the owner-occupancy rule. Decatur, DeKalb County and Gwinnett County each require the owner to live on the property that has the accessory unit. An investor who lives elsewhere cannot use those ADU rules.
City of Decatur: Duplexes and Walk Up Flats
Decatur is a city of 25,276 people (US Census Bureau estimate for July 1, 2025) inside DeKalb County. Its zoning rules are in the Unified Development Ordinance. The building types allowed in each district are listed in Article 3, and the lists for the four single-family districts each include "Duplex" and "Walk Up Flat," with the history note "(Ord. No. O-23-Z-01, § 5, 2-6-23)." VanPlex could not open the City of Decatur's own website, which returned an access error, so the only date this guide gives for the change is the one in the code's history notes: February 6, 2023.
The two building types are defined in Article 2. A duplex is "a building type designed to accommodate two principal dwelling units, vertically or horizontally integrated," with at most two units per lot and an entrance facing the primary street. A walk up flat is the same idea with "three to four principal dwelling units." The walk up flat table sets "3 min/4 max" units per building and adds four design rules:
- The ground story must be at least 10 feet high.
- The ground floor must sit between 2 and 4 feet above grade, the level of the ground.
- At least 20 percent of the ground story wall must be windows. The code calls this transparency.
- The entrance faces the street, and "no on-site parking is allowed between the building and the street."
The use table in Article 6 marks duplex and walk up flat with an "L" in R-85, R-60, R-50 and RS-17, and a "P" in RM-18, RM-22, RM-43 and PO. The code's key explains the letters. "P" is a permitted use. "L" is a limited use, which "indicates a use is permitted in the respective district, subject to a use standard." A limited use needs no rezoning. It has to meet the written standard for that use.
Lot sizes for a duplex or walk up flat in Decatur
| District | Minimum lot area | Minimum width | Minimum depth | Maximum lot coverage |
|---|---|---|---|---|
| R-85 | 15,000 sq ft | 85 ft | 150 ft | 40% |
| R-60 | 9,000 sq ft | 60 ft | 120 ft | 40% on a lot of 9,000 sq ft or more |
| R-50 | 5,000 sq ft | 50 ft | 100 ft | 58% on a lot of 5,000 to 5,499 sq ft, stepping down to 40% at 9,000 sq ft or more |
| RS-17 | 5,000 sq ft | 50 ft | None listed | 60% |
Source: Decatur Unified Development Ordinance, Secs. 3.1.3, 3.2.3, 3.3.3 and 3.4.3. The duplex and walk up flat rows carry the same figures as the detached house row in each district. RS-17 also has a site limit of 17 units per acre.
The lot rule is the same for one home and for four. In R-60, a detached house, a duplex and a walk up flat each need 9,000 square feet, 60 feet of width and 120 feet of depth. The code sets one lot size for all three building types. Lots smaller than the minimum follow a separate section of the code, Section 2.1.4, which VanPlex did not read.
The five-home inclusionary rule
Decatur's inclusionary housing standard applies to "any new development that creates at least five multiple-family dwelling units," and the same threshold applies to lots. A covered project "shall designate a minimum of ten percent of the total number of dwelling units or lots to be developed as inclusionary dwelling units." An inclusionary rule requires a share of new homes to be set aside as affordable housing. A walk up flat of four homes has one home fewer than the threshold. The code adds one rule for that building: "An ADU as an accessory use to a four-unit walk up flat shall be subject to the Standards for Inclusionary Dwelling."
City of Decatur: Accessory Dwelling Units and Short-Term Rentals
Decatur's ADU rules are in Article 6, added by Ord. No. O-21-Z-02 on October 18, 2021 and amended by O-23-Z-01. An ADU is allowed as an accessory use to a single-family house, a duplex or a walk up flat. The main limits are:
- One per lot. "Only one ADU may be created per lot of record."
- Size. No more than 800 square feet of floor area and no less than 300, "excluding any related garage area." It may not exceed 40 percent of the floor area of the principal dwelling.
- Bedrooms. No more than two.
- Owner on site. "The property owner must occupy either the principal dwelling unit or the ADU as their permanent residence for at least eight months out of each year," and may not collect rent on the unit the owner occupies.
- Paperwork. The building permit application includes a sworn, notarized statement from the owner.
The 40 percent rule can set a lower limit than 800 square feet. For a house of 1,500 square feet, 40 percent is 600 square feet. A second table applies to a detached unit: the Carriage House building type lists "800 SF max unit; 1,000 SF max with garage." Both rules apply to a detached ADU.
Decatur limits short-term rentals in small multi-unit buildings: "In duplexes, walk up flats, and stacked flats, no more than one dwelling unit per building may be rented or used at a time as a short term" rental. Occupancy is two people per sleeping room plus two, and "under no circumstances shall the maximum occupancy exceed ten persons."
One lending rule matters here. Decatur's zoning lets an owner add an ADU to a duplex. Fannie Mae's Selling Guide, section B2-3-04, says: "ADUs are not permitted with a two- to four-unit dwelling." Talk to a lender before you plan a duplex with an ADU, and see the financing page.
Unincorporated DeKalb County
DeKalb County had 774,394 residents on July 1, 2025 by the Census Bureau's estimate. Its zoning rules are in Chapter 27 of the County Code, and the use rules are in Article 4. They apply to land outside the county's cities.
ADUs by right since 2015
Section 4.2.3 says "attached and detached accessory dwelling units are permitted by right," which means no hearing or special permit is needed when the standards are met. The section also covers a unit made inside an existing house, such as a converted basement, wing or attic. It was adopted by Ord. No. 15-06 on August 25, 2015. The standards:
- "The minimum lot size shall be ten-thousand (10,000) square feet."
- The property owner, a term that includes titleholders and contract purchasers, "must occupy either the principal dwelling unit or the accessory dwelling unit as their residence, and possess a homestead exemption."
- Only one accessory dwelling unit of any type is permitted on a lot.
- A detached unit must be in the rear yard.
- Paved off-street parking must be provided for one additional vehicle.
- The unit may not exceed 900 square feet of heated floor area or 24 feet in height. Heated floor area leaves out the garage.
- On a site in a historic district, a certificate of appropriateness is required.
The homestead exemption test is the strict part. A homestead exemption is a property tax reduction for a home the owner lives in, so an owner who lives somewhere else cannot meet it. The property tax page explains how the exemption works in Georgia.
Duplexes and triplexes by district
DeKalb's use table, Table 4.1, marks "Dwelling, two-family" and the three-family dwelling as permitted in the RSM, MR-1, MR-2 and HR districts, in RNC, and in the mixed-use districts MU-1 to MU-5. The columns for RE, RLG, R-100, R-85, R-75 and R-60 are blank for those uses. The accessory dwelling, which the table describes as "guesthouse, in-law suite," is a permitted accessory use from RE through MR-2 and in MU-1 to MU-5. VanPlex read the columns by their position in the table text, so confirm the district of your lot and its row with the County before you rely on this summary.
A separate table limits the size of accessory buildings for single-family, two-family and three-family homes: 900 square feet on lots under 1 acre and 1,200 square feet on lots of 1 to 4.999 acres.
Sandy Springs, South Fulton and Gwinnett County
The rules in this section were read from each code through the publisher's text service. VanPlex did not open the public reader pages for these three codes, so they are named here without links. Search each government's code of ordinances for the section numbers given.
Sandy Springs (population 105,013)
Section 7.8.6.D of the Sandy Springs Development Code allows an "Accessory Dwelling, Guest House" on a lot with a single unit detached or attached home. "No more than 1 guest house per lot allowed." The unit may be attached or detached, may have a separate kitchen, and may sit over a garage. "Total heated floor area (HFA) must be less than 1,500 square feet," and the height limit is 2 stories. A detached guest house goes in the rear yard with 20 feet between buildings, and the setbacks of the principal building apply.
The same article defines a "Neighborhood Unit" as "two or more dwelling units on a lot designed to be at a scale that blends into a low-density neighborhood context." The standard allows one building per lot, a height of 2.5 stories and a street-facing width of 100 feet. "No more than 12 dwelling units per building are permitted," and "in RU- Districts, no more than 4 dwelling units per building are permitted." VanPlex did not read the use table that says which districts permit a Neighborhood Unit, so this guide does not say where one can be built.
City of South Fulton (population 112,820)
Section 303.09 of the South Fulton Zoning Ordinance allows a guest house with its own kitchen in the rear yard, under the setbacks of the principal building. The key sentence is: "No more than one guest house structure per lot may be used for occupancy by relatives, guest(s) or employees that work on the property without payment for rent." The heated floor area "shall be a minimum of 650 square feet and a maximum of 1500 square feet," or the structure may be a "Tiny House" of at most 400 square feet. The words "without payment for rent" mean this rule does not create a rental unit.
Unincorporated Gwinnett County (county population 1,018,099)
Section 210-140.10 of the Gwinnett County Unified Development Ordinance sets three main limits on an accessory dwelling: "No more than one accessory dwelling unit per primary dwelling unit." "The primary dwelling unit shall be owner-occupied." "The accessory dwelling unit shall not exceed 50% of the principal residence's heated floor area." The unit may be attached or detached. A detached unit goes in the rear yard, with side and rear setbacks of 10 and 15 feet in R-75, R-60, R-SR and TND, and 5 and 10 feet in R-IF. A Certificate of Occupancy for the unit is required before anyone lives in it.
Gwinnett also has a district written for small multi-unit buildings. Section 210-80.1 created the R-IF Residential In-Fill District by Ord. No. UDOA2023-00002 on September 26, 2023, and says: "This zoning district is intended primarily for missing middle housing." Missing middle housing is the planning term for duplexes, triplexes, fourplexes and similar small buildings. In the use table, duplex, triplex, fourplex and "multiplex" dwellings carry a "C" in R-IF and LRR, which the code defines as a conditional use subject to additional requirements. The same rows are blank for RA-200, R-LL, R-100, R-75 and R-60. A lot in one of those districts must first be rezoned to R-IF.
What Was Permitted in 2025
The US Census Bureau's Building Permits Survey counts new residential buildings authorized by permit, by the number of homes in the building. The 2025 annual files show where small multi-unit buildings were permitted in the metro area.
| Place | Population, July 1, 2025 | Two-unit buildings (homes) | Three-to-four-unit buildings (homes) |
|---|---|---|---|
| City of Atlanta | 529,110 | 78 (156) | 64 (236) |
| Fulton County Includes all of the City of Atlanta | 1,098,791 | 78 (156) | 66 (242) |
| DeKalb County | 774,394 | 1 (2) | 1 (4) |
| Cobb County | 793,345 | 0 | 2 (6) |
| Gwinnett County | 1,018,099 | 10 (20) | 2 (8) |
| Decatur | 25,276 | 0 | 0 |
| Sandy Springs 11 months reported | 105,013 | 0 | 0 |
| South Fulton | 112,820 | 0 | 0 |
| Marietta | 63,574 | 0 | 0 |
| Brookhaven | 59,643 | 0 | 0 |
Sources: US Census Bureau Building Permits Survey, 2025 annual files for places and counties; Vintage 2025 population estimates for cities and counties. County rows include the cities inside each county.
The whole Atlanta-Sandy Springs-Roswell metro area, with 6,482,182 residents, reported 94 two-unit buildings and 98 buildings of three or four units in 2025 (Census metro file). The City of Atlanta accounts for 78 of the 94 and 64 of the 98. Unincorporated DeKalb County reported one building of each kind, and unincorporated Gwinnett and unincorporated Cobb reported none. Gwinnett's county total of 10 two-unit buildings and 2 three-to-four-unit buildings therefore comes from its cities.
Decatur's figure is zero. Its code has listed duplexes and walk up flats in the single-family districts since the 2023 ordinance, and the 2025 permit file shows 30 one-unit buildings and no two-, three- or four-unit building. The survey counts new residential buildings authorized by permit.
State Rules That Apply in Every City and County
Four state-level facts hold across the metro area.
- No statewide ADU law. No bill on accessory dwelling units, lot sizes or missing middle housing is on the Governor's lists of signed legislation for 2025 or 2026. The House-passed ADU bill of 2026, HB 1166, is not on the 2026 list.
- A set hearing schedule for local upzoning. Under HB 155 (2025), a local government that amends its ordinance to let single-family districts hold multifamily uses must adopt the change at two regular meetings 15 to 45 days apart, after at least two public hearings held three to nine months before the final vote. That part of the act took effect July 1, 2025.
- The same loan limits. The FHFA county file for 2026 lists the same conforming loan limits for Fulton, DeKalb, Cobb, Gwinnett and Clayton counties: $1,066,250 for two units, $1,288,800 for three and $1,601,750 for four.
- An ADU can change the loan category. The FHA handbook counts a property with two homes and one ADU as a three- to four-unit property.
What This Page Does Not Cover, and What to Confirm
- Marietta. A keyword search of Division 712 of Marietta's zoning ordinance found no accessory dwelling text, and two other divisions were not read. This guide states no ADU rule for Marietta.
- Cobb County, Roswell and Brookhaven. Their codes were not researched.
- Which government your lot is in. Confirm with the county whether the lot is inside a city or in the unincorporated area, then read that government's code.
- Decatur's use standards. A duplex or walk up flat is a limited use in the single-family districts. Ask the City of Decatur for the use standard and for the rule on lots under the minimum size.
- DeKalb and Gwinnett district columns. Confirm the row for your district with the county planning staff.
Best For
- ✓ A Decatur lot that meets the district minimum, such as 9,000 square feet in R-60, for a duplex or a walk up flat of three to four homes.
- ✓ An owner who lives on the property in Decatur, unincorporated DeKalb or unincorporated Gwinnett and wants one accessory unit.
- ✓ A DeKalb lot of 10,000 square feet or more, where one ADU of up to 900 square feet is permitted by right.
Usually Fails When
- ✕ An investor who lives elsewhere plans an ADU in Decatur, DeKalb or Gwinnett. Each code requires the owner on site.
- ✕ A South Fulton guest house is planned as a rental. The code allows occupancy "without payment for rent."
- ✕ A fifth home is added in Decatur without planning for the ten percent inclusionary rule.
What To Verify Before Spending Money
- → Whether the lot is inside a city or in the unincorporated county, and its zoning district.
- → The use standard for a limited or conditional use, from the city or county planning office.
- → With a lender: how a duplex plus an ADU is classified for the loan.
Where to Go Next
Related on VanPlex: the Atlanta multiplex guide overview, rules in more Texas cities and the missing middle guide.
Frequently Asked Questions
Does Decatur allow duplexes in single-family neighborhoods?
What is a walk up flat in Decatur?
Can I build a fourplex in Decatur?
What are Decatur's ADU rules?
Do I have to live on site to have an ADU in Decatur?
Does Decatur's inclusionary rule apply to a fourplex?
Does DeKalb County allow ADUs?
How big can an ADU be in DeKalb County?
Where does DeKalb County allow duplexes?
Can I rent out a guest house in South Fulton?
What are the Sandy Springs guest house rules?
What is Gwinnett County's R-IF district?
Does Gwinnett County allow ADUs?
Official sources (checked October 2026)
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