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Decatur, GA Accessory Structures: ADU Rules (2026)

Some Restrictions

Compiled from the official code textEditor Martyn O'NeillLast verified September 2026

ADU rules in Decatur, GA, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.

Key Facts

Floor area range: 300 to 800 square feet
Share of main home: Max 40% of principal dwelling
Bedrooms: Two maximum
ADUs per lot: One
Owner residency: 8 months/year, no rent on that unit
Governing section: UDO Sec. 6.3.1.G and 6.8.3.A

ADU Eligibility Quick-Check

An Accessory Dwelling Unit (ADU) is a smaller, independent living unit on the same lot as a single-family home: converted garages, detached cottages, basement or attic conversions, and attached additions all qualify. Most states have streamlined ADU permitting since 2020, but local rules still control size, height, and setback.

Is your lot zoned single-family or multi-family residential?
Does your lot have at least 1,200 sq ft of buildable space?
Is your existing home owner-occupied (in most states this is not required, but some require it for ADU permits)?
Will the ADU stay under your state's size cap (commonly 850-1,200 sq ft for detached)?
Can you provide one off-street parking space (waived in many states within 0.5 mi of transit)?

If you answered 'yes' to most of these, you likely qualify in Georgia under recent ADU streamlining laws. The Decatur, GA rules below cover local size, height, and setback requirements.

Summary

In the City of Decatur, Georgia (DeKalb County), an accessory dwelling unit is a limited use allowed only behind a single-family detached house, duplex or walk up flat. UDO Section 6.8.3.A caps a Decatur ADU between 300 and 800 square feet, at no more than 40 percent of the principal home's floor area, with two bedrooms maximum and one ADU per lot.

Where an accessory dwelling unit is allowed as a limited use, it is subject to the following: ... 1.An ADU is only allowed as an accessory use to a single-family detached house, duplex, or walk up flat and shall be subject to the Standards for Specific Accessory Uses in Section 6.8.3.2.An ADU as an accessory use to a four-unit walk up flat shall be subject to the Standards for Inclusionary Dwelling in Section 6.3.1.F. and shall not incorporate a density bonus or parking reduction. ... 1.The design and size of the ADU shall conform to all codes which are required for any new construction.2.Only one ADU may be created per lot of record.3.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 at no time receive rent for the owner-occupied unit. ... 6.In no case can an ADU be more than 800 square feet of floor area, or less than 300 square feet of floor area, excluding any related garage area or other ancillary storage, or shall it exceed 40 percent of the floor area of the principal dwelling; nor have more than two bedrooms.

View official code

Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 28).

Full Breakdown

3 for the dimensional standards. A, cap floor area at no more than 800 square feet and no less than 300 square feet, excluding any attached garage or ancillary storage, and further cap it at 40 percent of the principal dwelling's floor area; an ADU cannot have more than two bedrooms, and a lot of record is limited to one ADU. The design and size of the unit must meet every building code that applies to new construction, and the ADU can be developed inside or attached to either an existing or a new principal dwelling.

Decatur's owner-occupancy rule is strict: the property owner must live in either the principal house or the ADU as a permanent residence at least eight months of every year and can never collect rent on the unit the owner occupies. A building permit application must include a sworn, notarized statement from the owner making that same commitment. Decatur treats an accessory structure that starts to look like an unauthorized second dwelling, complete with its own utilities and kitchen, as subject to the full zoning rules for a separate dwelling unit rather than the lighter ADU standards, which is why the ordinance ties the size caps to actual construction rather than to how the space is used day to day.

Parking for an ADU still has to satisfy the off-street parking table in Article 7 of the UDO. F and forfeits any density bonus or parking reduction.

Violations & Fines

Building or renting an ADU that exceeds the 800-square-foot cap, adds a third bedroom, sits on a lot that already has one, or is occupied without the owner meeting the eight-month residency and no-rent requirement is a zoning violation. The Zoning Administrator can deny or pull the certificate of occupancy, and an accessory structure that functions as an unauthorized second dwelling unit loses the lighter ADU standards and falls under the full dwelling-unit rules for its zoning district.

Frequently Asked Questions

How big can an ADU be in Decatur, Georgia?

Between 300 and 800 square feet of floor area, excluding any garage or ancillary storage, and never more than 40 percent of the principal dwelling's floor area, per UDO Section 6.8.3.A. The unit is also capped at two bedrooms and must meet every code that applies to new construction.

Does the property owner have to live on site?

Yes. Decatur requires the owner to occupy either the principal home or the ADU as a permanent residence at least eight months a year and forbids charging rent on the unit the owner lives in, confirmed by a notarized statement filed with the building permit application.

Can I build an ADU behind any house in Decatur?

Only if the principal structure on the lot is a single-family detached house, duplex, or walk up flat under Section 6.3.1.G. Only one ADU is allowed per lot of record, and it must be built to the dimensional and occupancy standards in Section 6.8.3.A.

Sources & Official References

[1]Decatur, Georgia Code of Ordinances (Municode)

Other rules in Decatur

Noise Ordinances: Quiet HoursLight Restrictions Noise Ordinances: Construction HoursSome Restrictions Shed & Carport RulesSome Restrictions Noise Ordinances: Decibel LimitsSome Restrictions Noise Ordinances: Barking DogsSome Restrictions Noise Ordinances: Amplified Music & Outdoor SoundSome Restrictions Parking Rules: Loading ZonesSome Restrictions

All Decatur rules

How Decatur compares: Easiest Cities to Build an ADU·Compare Decatur to another location·View the Georgia accessory structures overview

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