An ADU builder in Ann Arbor is a licensed contractor who designs and constructs accessory dwelling units — detached backyard units, garage conversions, attached additions, and junior ADUs (JADUs). Because an ADU is a complete second dwelling, the builder coordinates foundation, framing, plumbing, electrical, and HVAC work and pulls it through Ann Arbor's permit process and utility connections. Not every general contractor has built one, so the right builder is one with ADU-specific experience in Michigan.
What ADU Builders Cost in Ann Arbor [5][6]
Based on our Ann Arbor cost data, expect the following ranges from local ADU builders. Quotes for the same scope typically vary 20-40% between contractors, so getting at least three bids is the single best way to control cost.
| New Detached ADU (all-in) | $120,000-$240,000 |
| Cost per Sq Ft | $180-$300 |
| Garage Conversion | $60,000-$130,000 |
| Prefab / Modular ADU (installed) | $90,000-$180,000 |
| City Permit & Plan Review | 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 |
For a full line-item breakdown, see our Ann Arbor ADU cost guide. To confirm what you're allowed to build before you hire, review the Ann Arbor ADU rules (max detached size: 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; owner-occupancy: Not required — the owner-occupancy requirement was removed by the June 2021 amendments).
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How to Vet an ADU Builder in Ann Arbor
- License: Confirm a current contractor's license in Michigan and that it's in good standing. Ask for the license number and verify it with the state board.
- ADU-specific experience: Ask how many ADUs they've completed in or near Ann Arbor and request addresses or photos. ADU permitting and setbacks differ from a kitchen remodel.
- Portfolio & references: Get references from recent ADU clients and, if possible, visit a finished unit.
- Insurance: Verify general liability and workers' compensation coverage. Ask for a certificate of insurance.
- Written, detailed bid: Insist on an itemized, fixed-price or clearly-scoped bid — not a verbal estimate. It should state whether permits (Building and trade permit fees are based on construction valuation — confirm current fee schedule with the Ann Arbor Building Department), plan check (Zoning compliance is reviewed as part of the building-permit process; a property survey may be required to verify setbacks), and impact fees (None — Michigan law does not authorize municipal development impact fees; budget for water/sewer and utility connection charges instead) are included.
- Permit handling: Confirm they manage Ann Arbor's permit 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", typically No hearings required, so review runs on standard building-permit timelines — confirm current plan-review turnaround with Ann Arbor Planning Services (734-794-6265)) and who is responsible if revisions are required.
- Payment schedule: Avoid large upfront payments. A reasonable schedule ties payments to completed milestones.
Questions to Ask Before You Hire
- How many ADUs have you built in Ann Arbor in the last two years?
- Is your bid fixed-price, and what would trigger a change order?
- Are permits, plan check, and utility connection fees included?
- What's a realistic timeline, including permit review (No hearings required, so review runs on standard building-permit timelines — confirm current plan-review turnaround with Ann Arbor Planning Services (734-794-6265)) and construction?
- Who is my point of contact and how are delays communicated?
- What warranty do you provide on workmanship?
- Can you share three recent Michigan ADU client references?
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