ADU rules in Wauwatosa, WI — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
Wauwatosa allows accessory dwelling units (ADUs) under Title 24 (Zoning Code) of the Wauwatosa Municipal Code. The original ADU ordinance was adopted by the Common Council in 2019. ADUs may be detached structures, additions to a home or garage, or conversions of an existing portion of a home or garage. Properties must be in eligible residential zoning districts. Beginning in 2025, the City offers a limited number of $25,000 forgivable loans to qualifying homeowners building ADUs. Zoning approval and a building permit are required, administered by the Planning Division and the Building Safety Department.
Wauwatosa's zoning authority derives from Wis. Stat. Sec. 62.23, which authorizes cities to adopt zoning ordinances. Title 24 of the Wauwatosa Municipal Code is the city's Zoning Code, available through the Municode Library and the city's online code portal. The Common Council adopted Wauwatosa's ADU ordinance in 2019, allowing accessory dwelling units in eligible residential districts. Three configurations are recognized: a stand-alone (detached) ADU, an addition to a principal home or garage, or a conversion of part of an existing home or garage. The ordinance is intended to add affordable rental options, create income for homeowners, and support multigenerational living, seniors, and caretakers, while preserving neighborhood character. Standards governing maximum unit size, height, setbacks, lot coverage, design, and any owner-occupancy or parking requirements are set out in Title 24; consult the current code or Planning staff for the dimensional limits applicable to your district, since standards differ for detached vs. attached and converted ADUs. In 2025, the City launched a limited forgivable-loan program (up to $25,000) to help homeowners finance ADU construction; as of early 2026, roughly 35 homeowners had met with staff to discuss projects and two qualifying permits had been issued. To confirm eligibility for a particular property, contact the Wauwatosa Planning Division at (414) 479-3522 or planning@wauwatosa.net before designing the project. Both a zoning permit and a building permit are required.
Building or occupying an ADU without zoning approval and the required building permit is a violation of Title 24 of the Wauwatosa Municipal Code. Enforcement may include stop-work orders, citations, daily forfeitures under the city's general penalty provisions, and orders to remove or modify non-conforming structures. Renting an unpermitted unit can also raise issues with property insurance and state building code compliance.
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