How Ann Arbor Handles Accessory Structures: A Practical Guide

Ann Arbor maintains 111 local ordinances across all categories, and 9 of those deal specifically with accessory structures. Here is a breakdown of what the city actually requires, what is prohibited, and where Ann Arbor falls on the strict-to-permissive spectrum compared to other cities.

Shed Rules

Ann Arbor allows small sheds without permits (typically under 200 sq ft per Michigan Building Code). Larger structures require permits and must meet setbacks.

Key details: No Permit: Under 200 sq ft. Permit: Over 200 sq ft. Setbacks: 3 to 5 ft from property line. Snow Load: Must meet MI code.

Unpermitted structure: retroactive permit with penalty. Non-compliant setback: modification or removal. Habitation violation: immediate correction.

The rules around shed rules in Ann Arbor lean permissive, but that does not mean anything goes.

ADU Rules

Michigan has no statewide ADU mandate. Ann Arbor ADU policies depend on local zoning. Some Michigan cities have adopted ADU-friendly ordinances.

Key details: State Mandate: None. Local Policy: Varies by city. Typical Size: 600 to 800 sq ft max. Permit: Building permit required.

Unpermitted ADU: standard building code enforcement. Zoning violation: cease-and-desist + fines. Must bring to code or remove.

Garage Conversions

Ann Arbor may allow garage conversions to living space with building permits. No state law facilitating conversions - local zoning and parking requirements apply.

Key details: Permit: Building permit required. Parking: Replacement may be required. State Law: No facilitation statute. Insulation: Energy code compliance (cold climate).

Unpermitted conversion: standard building code enforcement. Must bring to code or restore. Safety violations: immediate correction.

Carport Rules

Ann Arbor requires permits for carport construction. Setback requirements, height limits, and lot coverage maximums apply.

Key details: Permit: Required. Side Setback: 3 to 5 feet typical. Lot Coverage: Counts toward maximum. HOA: May restrict or prohibit.

Unpermitted carports: stop-work orders, required removal or retroactive permitting with penalty fees. Fines $200 to $1,000.

Tiny Homes

Ann Arbor regulates tiny homes differently based on whether they are on a permanent foundation or on wheels. Zoning and minimum square footage requirements apply.

Key details: Foundation: Treated as dwelling. On Wheels: RV classification typically. Min Size: 400 to 800 sq ft varies. ADU Path: May allow as secondary.

Unpermitted dwellings: removal or retroactive permitting. Zoning violations: fines and required relocation. Occupancy without certificate: prohibited.

ADU Permits

Ann Arbor is among Michigan's earliest by-right ADU cities. The Unified Development Code (UDC) Section 5.16.4 (formerly Chapter 55 Zoning, amended by Ordinance 16-13 in 2016) permits accessory dwelling units on any lot containing a one-family or two-family dwelling. Permits issue through the Building Department (a2gov.org/BuildingPermits) under the Michigan Residential Code.

Key details: Authority: UDC Section 5.16.4. By-Right Since: Ord. 16-13 (2016). Max Size: 800 sq ft or 60%. State Code: MCL 125.1501 (PA 230). Permit Agency: Ann Arbor Building Dept.

Unpermitted ADU construction is a UDC violation enforced by Planning and Building. Municipal civil infraction citations under City Code Chapter 110 carry fines, daily continuing-offense penalties, and stop-work orders. Unpermitted units cannot be lawfully rented and are excluded from Housing Code Certification under Chapter 105.

Ann Arbor is more permissive than most cities when it comes to adu permits. That said, there are still limits.

ADU Rental Restrictions

Ann Arbor ADUs may be rented long-term only by the unit not occupied by the owner, under UDC 5.16.4 and Housing Code Chapter 105. The 2024 short-term rental ordinance (Chapter 117) bans non-owner-occupied whole-house STRs in single-family residential zones, limiting STR use of an ADU to homestays where the owner remains on the property.

Key details: Long-Term Rental: 1 unit only (owner-occ rule). Rental Registration: Required (Ch. 105). STR Whole-House SF: Banned (Ch. 117, 2024). Homestay STR: Allowed if owner on-site. Accommodations Tax: 5% city + 6% state.

Operating an unregistered rental is a Chapter 105 violation with fines and loss of Certificate of Compliance. Operating a non-owner-occupied whole-house STR in a banned zone is a Chapter 117 violation with escalating municipal civil infractions per Chapter 110 and possible STR registration revocation. Failure to remit accommodations tax exposes the operator to MCL 141.861 collection actions.

This is not one of those rules that cities tend to ignore. Ann Arbor actively enforces its adu rental restrictions requirements.

ADU Impact Fees

Ann Arbor cannot impose true development impact fees on ADUs because Michigan law forbids them. The Michigan Supreme Court in Bolt v. City of Lansing, 459 Mich 152 (1998), held municipalities lack authority to charge impact fees without specific statutory authorization. ADU costs are limited to Building Department permit fees and water/sewer connection charges.

Key details: Impact Fees: None (Bolt v. Lansing). Citation: 459 Mich 152 (1998). Building Permit: Per City fee schedule. Water/Sewer: Connection charge only. Property Tax: Taxable Value reassessment.

Bypassing permits avoids fees but exposes the property to stop-work orders, double permit fees on after-the-fact applications, and municipal civil infraction citations. Unpermitted utility connections may result in service disconnection by Ann Arbor Water/Wastewater until corrected.

If you are coming from a city with tighter rules, you will find Ann Arbor gives residents more flexibility on adu impact fees.

ADU Owner Occupancy

Ann Arbor requires owner-occupancy of an ADU property. UDC Section 5.16.4 mandates that the property owner reside in either the principal dwelling or the ADU as their primary residence. Only one of the two units may be rented to a non-owner. Both units must be registered under Ann Arbor Housing Code Chapter 105 if rented.

Key details: Owner-Occupancy: Required (UDC 5.16.4). Documented By: PRE (MCL 211.7cc). Rental Cap: 1 of 2 units. Rental Registration: Required (Ch. 105). Historic Districts: COA per Ch. 103.

Renting both the primary dwelling and the ADU to non-owners is a UDC violation, enforced as a municipal civil infraction under Chapter 110 with daily continuing-offense fines. Loss of Certificate of Compliance bars lawful occupancy and rent collection until restored. Rental of an unregistered unit triggers additional Housing Code citations.

The Bottom Line

Compared to many U.S. cities, Ann Arbor gives residents more room on accessory structures. 3 of the 9 rules here are rated permissive. But permissive does not mean unregulated. There are still requirements, and the city does enforce them when violations are reported.

This guide is based on Ann Arbor's current municipal code. Local rules can and do change, so check the individual ordinance pages for the latest details, penalties, and FAQs.