Compare ADU zoning rules across 3 Michigan cities. Average ADU score: 5.3/10.
| City | Max Size | Setbacks | Permit Fees | Build Cost | 1BR Rent | Score |
|---|---|---|---|---|---|---|
| Ann Arbor | 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 | 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 | Building and trade permit fees are based on construction valuation — confirm current fee schedule with the Ann Arbor Building Department | $120,000-$240,000 | $1,450-$1,650/mo | 7/10 |
| Detroit | Proposed: no more than the smaller of 1,200 sq ft or 60% of the principal dwelling's gross floor area (Sec. 50-12-466); not yet in effect | Proposed: standard 3 ft accessory-structure rear setback, with no rear setback required where the lot abuts an alley; existing accessory structures converted to ADUs may keep their footprint | Building permit fees based on construction value — confirm with Detroit BSEED once ADU rules take effect | $90,000-$200,000 | $950-$1,300/mo | 2/10 |
| Grand Rapids | 850 sq ft maximum and no more than 40% of the main house's gross floor area (ordinance §5.9.03 allows at least 400 sq ft in any case); greenspace requirements (30-60% depending on zone) can further limit buildable size | Detached ADU must be at least 3 ft from the rear lot line (special Building Code requirements if a wall is within 5 ft of the property line) | Building, trade, and water/sewer connection permit fees based on project scope — confirm current fee schedule with the Grand Rapids Development Center | $90,000-$200,000 | $1,400-$1,470/mo | 7/10 |
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