Ann Arbor permits ADUs by right in all R1, R2, R3, and R4 zoning districts on lots with a single-family dwelling — no public hearing or neighbor notification required. The original 2016 ordinance (ORD-16-16) was substantially liberalized in June 2021, when City Council removed owner-occupancy, extra parking, and minimum lot-size requirements and legalized newly constructed detached ADUs. Size is capped at 600 sq ft on lots under 7,200 sq ft and 800 sq ft on larger lots (or the main home's ground-floor area, whichever is less), and short-term rental of ADUs under 30 days is prohibited.
Zoning & Size Requirements [1][2][3]
Yes — Ann Arbor allows ADUs. A detached ADU can typically be up to the city's size limit under current Michigan and Ann Arbor zoning rules.
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| Allowed Zones | R1, R2, R3, and R4 districts, on lots containing one single-family dwelling (not permitted on lots with a duplex or multi-family building) |
| Max Size (Detached) | 600 sq ft on lots up to 7,199 sq ft; 800 sq ft on lots 7,200 sq ft or larger — or the ground-floor area of the main dwelling, whichever is less |
| Max Size (Attached) | Same tiered cap: 600 sq ft (lots under 7,200 sq ft) or 800 sq ft (lots 7,200 sq ft+), or the main dwelling's ground-floor area, whichever is less |
| Max Size (JADU) | Not applicable — Michigan cities have no separate JADU category |
| Max Height | 21 ft for an ADU in an accessory building (detached); 30 ft for an ADU within the main dwelling |
| Max Units | One ADU per single-family detached dwelling; ADU occupancy limited to 2 persons plus offspring, and 4 persons plus offspring combined across both units |
Setback Requirements [1][2][3]
Ann Arbor requires a rear setback of about 3 ft for a detached ADU, and no additional parking is required. Owner-occupancy is not required — you can rent it out without living on the property.
| Rear Setback | Allowed in the rear setback area if at least 3 ft from any lot line and all structures cover no more than 35% of the rear setback area; fire-rated walls required if 3-5 ft from a lot line |
| Side Setback | Detached ADU allowed in the side setback area if farther from the street than the main building (and neighbors' main buildings) and at least 3 ft from any lot line; fire-rated walls if 3-5 ft. Attached ADUs may not be in the required side setback |
| Front Setback | Not permitted within the required front setback area (average of buildings within 100 ft, up to 40 ft max, in established neighborhoods) |
| Parking Required | No additional parking required — the parking requirement was removed by the June 2021 amendments |
| Owner Occupancy | Not required — the owner-occupancy requirement was removed by the June 2021 amendments |
| Min Lot Size | No minimum lot size (removed in 2021); lot area only determines the 600 vs 800 sq ft size tier |
Permit Process & Fees [4]
An ADU permit in Ann Arbor typically costs Building and trade permit fees are based on construction valuation — confirm current fee schedule with the Ann Arbor Building Department and takes No hearings required, so review runs on standard building-permit timelines — confirm current plan-review turnaround with Ann Arbor Planning Services (734-794-6265), through a ministerial, by-right review.
| Approval Process | By-right building permit through Planning Services/Building Department — no public hearing or neighborhood notification. Submit building plans plus trade permits (mechanical, plumbing, electrical), grading application/impervious area checklist, and a Michigan Energy Code compliance form for new structures. Historic District lots need a Certificate of Appropriateness first. Rented ADUs must register with Rental Housing Services and get a Certificate of Occupancy |
| Review Timeline | No hearings required, so review runs on standard building-permit timelines — confirm current plan-review turnaround with Ann Arbor Planning Services (734-794-6265) |
| Permit Fees | Building and trade permit fees are based on construction valuation — confirm current fee schedule with the Ann Arbor Building Department |
| Impact Fees | None — Michigan law does not authorize municipal development impact fees; budget for water/sewer and utility connection charges instead |
| Plan Check | Zoning compliance is reviewed as part of the building-permit process; a property survey may be required to verify setbacks |
| Pre-Approved Plans | No city pre-approved ADU plan library — confirm with Ann Arbor Planning Services |
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Construction Costs [5][6]
Building an ADU in Ann Arbor typically costs $120,000-$240,000 ($180-$300 per sq ft); a garage conversion runs $60,000-$130,000.
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| Average Build Cost | $120,000-$240,000 |
| Cost per Sq Ft | $180-$300 |
| Garage Conversion | $60,000-$130,000 |
| Prefab ADU (Installed) | $90,000-$180,000 |
Finance Your ADU Project
Most ADU projects are funded through HELOCs, construction loans, or cash-out refinancing. Compare rates from top lenders.
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Rental Income Potential [7][8]
A 2-bedroom ADU in Ann Arbor rents for around $1,900-$2,000/mo, an estimated 6-10% annual return.
| Avg Rent (1 Bedroom) | $1,450-$1,650/mo |
| Avg Rent (2 Bedroom) | $1,900-$2,000/mo |
| Short-Term Rental | No — leasing or renting an ADU for less than 30 days is prohibited |
| Est. Annual ROI | 6-10% annual return |
Explore Prefab ADU Options
Prefab ADUs can save 20-40% vs. traditional construction and cut build time in half.
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Recent Law Changes
What's Changed Recently
- June 2021: City Council amendments removed owner-occupancy, additional parking, and minimum lot-size requirements, legalized newly constructed detached ADUs, and expanded eligibility across R1-R4 districts
- September 2023: Planning Services published an updated ADU Guidebook consolidating design, setback, occupancy, and application requirements
- Since 2016, 43 ADU applications have been submitted citywide — adoption accelerated after the 2021 liberalization
Tips for Building an ADU in Ann Arbor
- Check the city zoning map first: your lot must be R1-R4 with a single-family home — duplex and multi-family lots don't qualify
- Keep detached ADUs at least 5 ft from lot lines to avoid the fire-rated wall requirement that kicks in between 3 and 5 ft
- If your lot is 7,200 sq ft or larger you get the 800 sq ft cap instead of 600 sq ft — verify lot area with a survey before designing
- Budget for Michigan's 42-inch frost-depth footings and plan a spring construction start; winter foundation work adds cost
- In a Historic District, secure your Certificate of Appropriateness before submitting building plans — it's a prerequisite for permit review
ADU Builders in Ann Arbor
Looking for an ADU builder in Ann Arbor? ADU projects need a contractor experienced with local zoning, the permit process, and utility connections — not every general contractor has built one. We match Ann Arbor homeowners with experienced local ADU contractors who provide free, no-obligation quotes. Getting at least three bids typically saves 20-40% on the same scope.
Sources & References
All data on this page is sourced from official government records and verified market data. View our full methodology.
- Accessory Dwelling Units | City of Ann Arbor city_website — Accessed 2026-07-10
- City of Ann Arbor Accessory Dwelling Unit Guidebook (September 2023) city_website — Accessed 2026-07-10
- ADUs Unbound — Ann Arbor Observer news_media — Accessed 2026-07-10
- City of Ann Arbor ADU Guidebook — Application Process city_website — Accessed 2026-07-10
- How Much Does It Cost to Build an ADU? — HomeGuide news_media — Accessed 2026-07-10
- How Much Does an ADU Cost to Build? — Angi news_media — Accessed 2026-07-10
- Average Rent in Ann Arbor, MI — RentCafe news_media — Accessed 2026-07-10
- Average Rent in Ann Arbor, MI — Zumper news_media — Accessed 2026-07-10
Frequently Asked Questions
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