Decatur, AL Accessory Structures: ADU Rules (2026)
ADU rules in Decatur, AL, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- Main structures per lot
- One, plus permitted accessory structures
- Living quarters in accessory buildings
- Not allowed
- Only exception
- Civil defense agency approved protective shelters, temporary
- Mobile homes
- Only in authorized parks, sales offices, construction sites
- Corner lot accessory rule
- Within 25 feet of rear line, front yard depth setback
- General penalty
- $1 to $500 per offense under § 1-8
Summary
In the City of Decatur, Alabama, a residential lot gets one main structure plus permitted accessory structures, and City Code § 25-18 says accessory structures shall not include living quarters. The only exception is a protective shelter approved by the civil defense agency, which can provide temporary living quarters. Mobile homes and trailers are also barred outside authorized parks.
It is the intent of this chapter that there shall be but one main structure plus any permitted accessory structures on any lot used for residential purposes; also, the accessory structures shall not include living quarters except that, in all districts, protective shelters approved by the civil defense agency may provide temporary living quarters. ... Trailers, buses, mobile homes, or any other structures so built to be, or give the reasonable appearance to be, mobile in character of its construction will not be permitted in any district for any use other than for the purpose of transportation or transportation enterprises; except that mobile homes may be utilized as residences when located within duly authorized mobile home parks, as offices for duly authorized mobile home parks, as offices for mobile home sales, and as temporary construction offices on job sites with uses incidental thereto, subject to the other codes and ordinances of the city pertaining thereto.
Full Breakdown
Section 25-18 of the Code of Decatur, Alabama states the city's intent that there shall be but one main structure plus any permitted accessory structures on any lot used for residential purposes. It then closes the door on a second home in a backyard building: accessory structures shall not include living quarters. A detached garage apartment, a converted shed or a guest cottage on the same lot as a house therefore falls outside what § 25-18 allows. The single exception is that in all districts, protective shelters approved by the civil defense agency can provide temporary living quarters.
The section also controls the workaround of putting a trailer on the lot. Trailers, buses, mobile homes, or any structure built to be, or that gives the reasonable appearance of being, mobile are not permitted in any district for any use other than transportation or transportation enterprises. Mobile homes can serve as residences only inside duly authorized mobile home parks, as offices for those parks or for mobile home sales, and as temporary construction offices on job sites.
Related standards sit in the same chapter. Section 25-14 requires yards and lot area for every structure and forbids counting one building's open space for another. Section 25-20 sets corner lot accessory structures within 25 feet of the rear lot line back to the minimum front yard depth on the side street. Where a carport or porch sits within five feet of the main structure in the R districts, the zoning schedule treats it as part of the main building. The Board of Zoning Adjustment handles uses permitted on appeal under § 25-13.
Violations & Fines
Section 25-18 has no penalty clause of its own, so § 1-8 applies: a misdemeanor punishable by a fine of not less than $1.00 nor more than $500.00, with up to six months of imprisonment or hard labor at the municipal judge's discretion, and each day of continued violation counted as a separate offense. The city building director issues zoning permits and enforces the chapter.
Frequently Asked Questions
Can I build a garage apartment in Decatur, Alabama?
Can I put a mobile home or trailer behind my house in Decatur?
How many houses can be on one residential lot in Decatur?
Who decides exceptions to the zoning rules in Decatur?
Sources & Official References
Other rules in Decatur
How Decatur compares: Easiest Cities to Build an ADU·Compare Decatur to another location·View the Alabama accessory structures overview
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