Garage conversion rules in Madison, WI — sometimes called garage-to-ADU or accessory living unit conversions — govern permits, ceiling height, egress, and parking replacement.
Garage conversions to habitable space require a building permit in Madison and must meet WI Uniform Dwelling Code for egress, insulation, and ventilation. Converting to an ADU follows MGO 28.151 with parking replacement if required.
Converting a garage to habitable space in Madison requires a building permit from Building Inspection. The work must meet WI Uniform Dwelling Code (SPS 320-325) requirements for minimum ceiling height (7 feet), egress windows in any new sleeping room, insulation to current energy code, mechanical ventilation, and smoke and CO alarm systems. If the conversion creates an independent unit with kitchen and bath, it becomes an ADU subject to MGO 28.151 and its 800 square foot cap and owner-occupancy rule. Removing a required off-street parking space typically requires replacement elsewhere on the lot, though waivers are available downtown and along transit corridors. Exterior changes such as new windows or filling in the garage door may require Plan Commission review in historic districts. Electrical and plumbing work requires separate permits and licensed contractors.
Unpermitted conversions can trigger stop-work orders, double permit fees, and requirement to restore original condition.
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See how Madison's garage conversions rules stack up against other locations.
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