ADU rules in Alabama
Representative cities: Birmingham, Montgomery.
ADU permit rule
Permit requiredCase by casecity authority
Fee basis
Valuation-based; set by the issuing city or county.
Typical timeline
Varies
Setback
—
Area threshold
Not size-exempt
Exempt if
None — an ADU always requires a building permit where local zoning allows it.
Go / no-go
case-by-case
Alabama has no statewide ADU (accessory dwelling unit) law. ADUs are allowed only where the local zoning ordinance permits them — for example, Birmingham has rezoned to allow ADUs in certain residential zones. When an ADU is permitted by zoning, a full building permit is required.
ADU official sources: Alabama Building Commission — Building Codes · City of Birmingham — Building Permits
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Frequently asked questions
Do I need a permit to build an ADU in Alabama?
Per Alabama rules, an ADU is "yes" for a permit and the authority is "city". Alabama has no statewide ADU (accessory dwelling unit) law. ADUs are allowed only where the local zoning ordinance permits them — for example, Birmingham has rezoned to allow ADUs in certain residential zones. When an ADU is permitted by zoning, a full building permit is required. Always confirm with the issuing building department.
How big can an ADU be in Alabama?
Size limits for an ADU in Alabama are set by local zoning — verify with your city building department.
What are the ADU setbacks in Alabama?
Setback rules vary by city in Alabama; confirm with the local planning or building department.
How much does an ADU permit cost in Alabama?
Fee basis: Valuation-based; set by the issuing city or county.