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Zoning Guide

ADU Rules in Mobile, Alabama

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ADU Rules in Mobile, Alabama

Mobile is Alabama's only port city and permits accessory dwelling units (ADUs) in residential areas under its Zoning Ordinance. Alabama has no statewide ADU law, giving Mobile full local control over ADU regulations.

Permitted ADU Types

  • Detached ADU: A separate structure on the same residential lot
  • Attached ADU: An addition to the main house with its own entrance and cooking facilities
  • Accessory Structure Conversion: Converting a garage or workshop to a dwelling unit

Size Limits

ADU Type Maximum Size
Detached ADU 900 sq ft or 45% of primary dwelling
Attached ADU 45% of primary dwelling floor area
Conversion ADU Existing footprint

Setbacks

  • Front: Must meet base zone standard (typically 25 ft in residential zones)
  • Side: 5 feet minimum
  • Rear: 10 feet minimum
  • Separation from primary: 10 feet minimum for detached ADUs

Height

  • Maximum 15 feet for detached ADU in most residential zones
  • Attached ADU cannot exceed primary dwelling height

Owner Occupancy

The property owner must occupy either the primary dwelling or the ADU. This requirement helps preserve neighborhood character and limits speculative investment.

Parking

One additional off-street parking space is required for the ADU. The space must have an improved surface (paved or gravel).

Flood Zone Considerations

Mobile has significant flood-prone areas. ADUs in FEMA flood zones must comply with floodplain regulations, which may require elevated foundations. Check the FEMA Flood Map Service Center before planning.

Permit Process

  1. Flood zone check: Verify flood zone status at FEMA MSC
  2. Zoning check: Confirm ADU eligibility with Mobile Planning & Zoning
  3. Submit plans: Architectural drawings with site plan
  4. Zoning review: Staff review for compliance
  5. Building permit: Applied through the Building Services Department
  6. Inspections: All required phases must pass inspection
  7. Certificate of Occupancy: Required prior to occupancy

Contact

Mobile Planning & Zoning Department 205 Government Street, Mobile, AL 36602 Phone: (251) 208-7090 Website: cityofmobile.org/planning

Disclaimer: Verify current requirements with the City of Mobile Planning & Zoning Department before starting any project.

More about Mobile Zoning

Sources

  1. Mobile City Code — Zoning Regulations·library.municode.com·Accessed 2026-04-07·Direct link
  2. City of Mobile Planning & Zoning Department·cityofmobile.gov·Accessed 2026-04-07·Direct link

FAQ

Are ADUs legal in Mobile, Alabama?
Yes. Mobile allows accessory dwelling units in residential zoning districts. The regulations depend on your specific zone designation and lot size.
What is the maximum ADU size in Mobile?
Accessory dwelling units in Mobile are generally limited to 900 square feet or 45% of the primary dwelling's floor area, whichever is less.
Does Mobile require owner occupancy for an ADU?
Yes. Mobile's zoning code typically requires that the property owner reside in either the main house or the accessory dwelling unit.