ADU Rules in Ann Arbor, Michigan

Ann Arbor is the Washtenaw County seat with a population of about 123,000, home to the University of Michigan (U-M) — one of the largest and most prestigious public universities in the United States. Ann Arbor is a progressive, walkable city with a strong housing affordability challenge driven by UMich enrollment and employment. The city has been a leader in Michigan on allowing ADUs broadly in residential zones. Michigan has no statewide ADU preemption law — Ann Arbor's local Zoning Ordinance governs.

Ann Arbor Zoning Ordinance

The City of Ann Arbor Zoning Ordinance governs all land use in Ann Arbor. The city has been progressive on ADU policy, recognizing that accessory units help address the city's housing shortage near UMich.

Permitted ADU Types

Per Ann Arbor Zoning Ordinance (verify current standards — policy has evolved):

• Detached ADUs (Accessory Dwelling Units): Broadly allowed in residential zones
• Attached ADUs: Additions with separate entrance
• Interior conversions: Basement, attic, and other conversions
• Garage conversions: Converting existing attached/detached garages

Ann Arbor has been expanding ADU allowances — verify current specific standards.

Size Limits

Per Ann Arbor Zoning Ordinance:

• Maximum ADU floor area per zone (typically capped as percentage of primary dwelling or absolute limit)
• Lot coverage restrictions

Setbacks

Per Ann Arbor residential zone:

• Rear: Minimum setback
• Side: Minimum setback

Ann Arbor may allow reduced setbacks for certain ADU types — verify current standards.

University of Michigan Context

UMich creates strong rental housing demand. Ann Arbor may have rental registration or licensing requirements for rental properties. Verify current rental registration requirements.

Huron River and Wetlands

Parts of Ann Arbor near the Huron River may be in FEMA flood zones. Michigan wetland regulations (EGLE) apply to properties near wetlands.

Historic Districts

Ann Arbor has local historic districts. Properties in historic districts require review by the Ann Arbor Historic District Commission.

Permit Process

1. Verify zoning: Ann Arbor Planning Division
2. Historic District review: If in a local historic district
3. Check flood zone/wetlands: If near the Huron River or wetlands
4. Submit plans: Ann Arbor Building Division
5. Building permit and inspections
6. CO: Required before occupancy

Contact

City of Ann Arbor Planning Division 301 E. Huron Street, Ann Arbor, MI 48104 Phone: (734) 794-6000 Website: a2gov.org/planning

Disclaimer: Michigan has no statewide ADU law. Ann Arbor has been progressive on ADU policy — verify current standards with the city before starting any project.