Detroit, MI Accessory Structures: ADU Impact Fees (2026)

Michigan is one of a handful of states whose courts have held that municipalities lack general authority to impose development impact fees on new residential construction without specific statutory authorization (Bolt v. City of Lansing, 459 Mich 152 (1998)). As a result, Detroit's ADU costs are limited to legitimate user charges: BSEED building permit fees calculated from construction valuation (Chapter 8 of the City Code, BSEED fee schedule), plan review fees, mechanical/electrical/plumbing permit fees, and water/sewer tap fees set by the Detroit Water and Sewerage Department (DWSD) based on the actual capacity of the service connection. There is no Detroit Public Schools impact fee, no parks fee, no transportation impact fee, and no affordable-housing in-lieu fee tied to an ADU. Property taxes will adjust based on the State Equalized Value (SEV) change after the ADU is added, but that is a property tax consequence, not an impact fee. Applicants for ADUs that share existing water and sewer lines with the primary dwelling typically pay only minimal additional DWSD fees.