ADU Cost in Michigan in 2026

ADU costs in Michigan range from $55,000 for a basic garage conversion in Flint to $292,000+ for a high-end ADU in the Birmingham/Troy suburban market. The most common Grand Rapids build — a 600 sq ft mid-range ADU — costs $110,000 to $175,000. Ann Arbor runs 15–20% higher. Detroit's carriage house conversion — if you have a pre-1940 structure — costs $65,000–$145,000 and offers the best Detroit ROI.

Detroit's R1 and R2 residential zone code limits detached ADU construction to the conversion of pre-1940 carriage houses — structures originally built as garages or carriage storage before 1940. New detached ADU construction is not permitted in most of Detroit's R1/R2 neighborhoods. If your property has a pre-1940 carriage house, this is a strong and relatively low-cost conversion opportunity ($65,000–$145,000). If it doesn't, an attached ADU or interior conversion is the more accessible path.

Yes — Grand Rapids is the most ADU-progressive major city in Michigan. ADUs are permitted by right in nearly all residential zones with no owner-occupancy requirement, no additional parking requirements, and a 400–850 sq ft size range. The city removed the previous owner-occupancy and parking restrictions to facilitate more ADU development. Short-term rentals under 30 days remain prohibited. Grand Rapids' growing tech and healthcare economy creates strong long-term rental demand.

Ann Arbor has one of the tightest rental markets in the Midwest — driven by University of Michigan students, faculty, medical staff, and a growing biotech sector. ADU rents average $1,700–$2,400/mo for a 1BR unit, and well-located studios near Central Campus can exceed this. The size cap (600 sq ft on smaller lots, 800 sq ft on larger lots) means Ann Arbor ADUs are dense urban units rather than spacious cottages — design for maximum livability within the cap.

It varies by city. Both Grand Rapids and Detroit prohibit short-term rentals under 30 days in ADUs. Traverse City and other northern Michigan resort communities have their own STR frameworks — some permissive, some increasingly restrictive. If STR income is your goal, verify the specific municipality's current STR ordinance before designing. Michigan has no statewide STR regulation, so rules can differ significantly between neighboring townships.

A mid-range 600 sq ft ADU in Grand Rapids costs $120,000 to $170,000 all-in and generates $1,200 to $1,600 per month in long-term rental income. Cash-on-cash ROI runs 10–12%, with a payback period of 10–12 years. Ann Arbor offers higher rents ($1,700–$2,400) but higher costs ($140,000–$210,000), producing comparable ROI. Detroit carriage house conversions offer the best ROI in the state at $65,000–$145,000 build cost with $900–$1,200/mo income.