ADU rules in Winnebago County, WI — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
Winnebago County administers zoning in unincorporated towns under Wis. Stat. §59.69. The cities of Oshkosh, Neenah, Menasha, and Appleton (the small Winnebago portion) and incorporated villages zone independently. Wisconsin has no statewide ADU mandate; 2025 Assembly Bill 449 proposing one is not enacted.
The Winnebago County Planning and Zoning Department enforces the County Zoning Ordinance under Wis. Stat. §59.69, which authorizes counties to regulate land use in unincorporated areas outside cities and villages. Cities (Oshkosh, Neenah, Menasha) and villages administer their own zoning ordinances. Any new dwelling unit — primary or accessory — must comply with the Wisconsin Uniform Dwelling Code (Wis. Admin. Code SPS 320-325) and obtain a sanitary permit if served by a private onsite wastewater treatment system. The county Allowed Uses FAQ directs residents to contact the county or the local town zoning office with parcel information to confirm whether a second dwelling unit is permitted on a given lot.
Zoning violations under Wis. Stat. §59.69(11) are subject to forfeitures set by ordinance plus daily continuing penalties. Unpermitted dwelling units may require removal or after-the-fact permits.
Winnebago County, WI
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Winnebago County, WI
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Winnebago County, WI
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Winnebago County, WI
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Winnebago County, WI
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Winnebago County, WI
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See how Winnebago County's adu rules rules stack up against other locations.
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