5 county-level rules, plus city-specific rules for 1 city in Washtenaw County, Michigan.
Verified from official government sources
Washtenaw County does not zone land; the City of Ann Arbor allows one ADU per single-family lot. The owner must live in the ADU or main house, minimum 5,000 sq ft lot, and rentals under 30 days are banned.
Ann Arbor City Code 5:10.2(4)(d)
An ADU is permitted on a parcel that has one single-family dwelling as the permitted principal use. The owner shall occupy either the ADU or the single-family dwelling on the property... Leasing or rental of the ADU for less than 30 days is prohibited.
In Ann Arbor, accessory buildings like sheds may not exceed 21 feet in height. Sheds 200 sq ft or larger need a building permit; smaller sheds still need a zoning compliance permit. Detached sheds must sit at least 3 feet from lot lines.
Ann Arbor Accessory Building Guidelines (Zoning Ordinance)
Accessory buildings may not exceed 21 feet in height, measured from the midpoint of the pitched roof. Accessory buildings that are 200 sq. ft. in size or greater require a building permit. Structures that are less than 200 sq. ft. in size do not require a building permit but still require a zoning compliance permit.
Ann Arbor accessory buildings may not be used as sleeping rooms or dwellings, so a garage cannot simply become living space. Converting a detached garage into habitable space is only allowed as a permitted ADU meeting the city's ADU standards.
Ann Arbor Accessory Building Guidelines (Zoning Ordinance)
Accessory buildings may NOT be used as a sleeping room or dwelling unit. As a result, accessory buildings may not include utilities for both bathrooms and kitchens.
Carports are treated as accessory buildings in Ann Arbor. They may not exceed 21 feet in height, and an attached carport may not occupy any part of the required side open space. Detached carports must stay at least 3 feet from lot lines.
Ann Arbor Accessory Building Guidelines (Zoning Ordinance)
Examples of accessory buildings include garages, carports, garden sheds, workshops, gazebos, pergolas, decks, and pools... Attached accessory buildings, such as a garage, may not occupy any portion of the required side open space.
Neither Washtenaw County nor Ann Arbor has a tiny-home-specific ordinance. A permanent tiny house is regulated as either an accessory dwelling unit or a single-family dwelling under the Michigan Residential Code; accessory buildings may not be lived in.
1 cities in Washtenaw County have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.
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