ADU rules in Brookfield, WI — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
The City of Brookfield Zoning Code (Title 17) does not authorize accessory dwelling units (ADUs) as a permitted accessory use in its R-1 through R-4 residence districts. The code regulates only "accessory buildings" - garages, sheds, and yard maintenance structures - which cannot contain a separate dwelling unit. On parcels of 12,000 sq ft or less, total accessory building square footage is capped at 600 sq ft (Ch. 17.136). Accessory buildings have a maximum height of 15 ft in R-2 and minimum side and rear yard offsets of 5 feet for detached garages and yard maintenance buildings. Wis. Stat. Sec. 62.23 grants the city its zoning authority.
Brookfield's zoning code at Title 17 establishes residential districts (R-1 through R-4) that permit one single-family dwelling per lot, with one attached garage of at least 200 sq ft required per dwelling unit. Chapter 17.136 (Miscellaneous Use and Design Restrictions) governs accessory buildings: all garages (attached or detached) and all other buildings that are not the principal building on the parcel are counted as accessory building square footage. Parcels of 12,000 sq ft or less are limited to 600 sq ft of accessory building area. The minimum side and rear yard offsets for detached garages and yard maintenance buildings are 5 feet. Other accessory buildings must comply with the broader principal-building setbacks of the underlying district. The Brookfield code does not contain a permitted use category for an accessory dwelling unit, accessory living quarters, or in-law suite separate from the principal residence, so adding a kitchen and full living facilities to an accessory building is not permitted by right. Property owners seeking a second dwelling on a single lot would need to pursue a zoning amendment, conditional use, or variance through the Brookfield Plan Commission and Board of Zoning Appeals. Wisconsin has not enacted a statewide ADU preemption law; municipal authority over zoning derives from Wis. Stat. Sec. 62.23. Verify current rules by contacting the City of Brookfield Community Development Department at (262) 782-9650.
Construction of a dwelling unit within an accessory building, or construction of any accessory building exceeding the 600 sq ft cap on small parcels, without proper permits violates Title 17. The City of Brookfield enforces zoning through its Inspection Services Department; remedies typically include stop-work orders, after-the-fact permit requirements, and orders to remove or modify nonconforming structures. Wis. Stat. Sec. 62.23(8) authorizes municipal enforcement and forfeitures.
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