ADU rules in Madison, WI — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
Madison legalized accessory dwelling units citywide in 2013 under MGO 28.151. ADUs are allowed in all residential districts subject to size, owner-occupancy, and parking standards. One of the first Midwestern cities to embrace ADUs.
Madison was an early Midwestern ADU pioneer, authorizing accessory dwelling units citywide in 2013 through MGO 28.151 (formerly 28.032). ADUs are permitted in all residential zoning districts including SR-C, TR, and most higher-density zones. Key standards: the ADU must be clearly subordinate to the primary dwelling, capped at 800 square feet or 75 percent of the primary unit floor area (whichever is less), and either attached, inside, or detached on the lot. Owner occupancy of either the primary or the ADU is required. One additional off-street parking space is required unless waived in the Downtown Core or along frequent transit corridors. Building permits follow the WI Uniform Dwelling Code. Short-term rental of an ADU is permitted only if it is the owner's principal residence and properly licensed. Conditional use review is required in some historic districts.
Contact your local code enforcement office for specific penalty information.
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Side-by-side rule comparisons with other cities in Dane County.
See how other cities in Dane County handle adu rules.
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