ADU rules in Mosinee, WI — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
The City of Mosinee's Zoning Code (originally updated in 1998) is administered by the City Clerk's office and Building Inspector and codified in the Code of Ordinances on Municode. Mosinee has not adopted a stand-alone accessory dwelling unit (ADU) chapter; instead, additional dwelling units are governed by the underlying residential zoning district standards (single-family, two-family, multi-family) plus accessory use and accessory structure provisions. A second dwelling unit on a single-family lot generally is not a permitted accessory use unless the lot meets the density, lot area, and dimensional requirements of a two-family or multi-family district. Building permits and zoning permits are required and issued through the City of Mosinee Building Permits process.
Mosinee's zoning authority is Wis. Stat. Sec. 62.23, which authorizes cities to adopt zoning ordinances regulating the use of buildings and the density of population. The City of Mosinee Zoning Code is referenced from the city website and the Code of Ordinances hosted at library.municode.com/wi/mosinee. Per the city's zoning page, the code categorizes parcels into residential, commercial, and industrial districts, with single-family residential districts intended for one principal dwelling per lot. Wisconsin does not have a state-level statute mandating that municipalities permit ADUs by right (unlike California or Oregon), so the ability to add a second unit is determined entirely by local ordinance and district-specific standards. In Mosinee, owners seeking to add a second self-contained dwelling typically must (a) confirm the lot is in a district that allows two-family or multi-family dwellings, or (b) pursue a rezoning, conditional use, or variance through the Plan Commission and Common Council. Detached accessory structures (garages, sheds) are permitted as accessory uses to a principal residential use but are not authorized as separate dwelling units absent express zoning approval. All construction triggers a state Uniform Dwelling Code (UDC) building permit through the city's contracted building inspector, plus zoning review through the City Clerk's office (715-693-2275, clerks@mosinee.wi.us). Confirm current district standards directly with the city before beginning design or construction.
Constructing or occupying a second dwelling unit without the required zoning approval and Uniform Dwelling Code building permit is a violation of the Mosinee zoning code and Wis. Stat. Sec. 101.65 (UDC enforcement). Enforcement may include stop-work orders, citations, daily forfeitures under the city's general penalty provisions, and orders to remove or convert the unauthorized unit. Connecting a second unit to municipal water or sewer without authorization is independently enforceable by the utility.
Mosinee, WI
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Mosinee, WI
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Mosinee, WI
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Mosinee, WI
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