ADU & Small-Format Zoning Rules Across Dane County.
ADU rules vary significantly by municipality across Dane County. Select your city or village below to see current zoning requirements, setbacks, and feasibility scores.
ADU Regulations Vary by Municipality Across Dane County
We’ve laid out what you need to know for Madison, Fitchburg, Middleton, Sun Prairie, and beyond — and we verify every detail before your project starts. Madison allows a 1,000 sq ft footprint and 3 ft side and rear setbacks. The current rules are on the Madison ADU regulations page. We track 21 Dane County municipalities.
Check Feasibility on My Property →Wisconsin granted municipalities broad authority over ADU regulations, which means there’s no single statewide standard. What’s allowed in Madison may not be allowed in Middleton. Setbacks, maximum unit sizes, owner-occupancy requirements, and permit fees all vary by jurisdiction — and some municipalities update their codes frequently.
Before any Boundless project starts, we run a complete feasibility check against the current code for your specific parcel. The information on this page is a reference — not a substitute for that review.
ADU Regulations by Municipality
The permit history and the seven zoning reforms are in the 2026 State of ADUs in Dane County.
Common ADU Regulation Categories
Regardless of municipality, these are the regulatory areas that affect every ADU project in Dane County. Understanding them early prevents surprises later.
ADUs are only permitted in certain zoning districts. Most single-family and two-family residential zones qualify, but mixed-use and commercial zones have different rules. Your parcel’s zoning classification is the first thing we verify.
Each municipality publishes its own cap. Madison and Sun Prairie allow 1,000 sq ft, and in those cities every Boundless model from A-360 (360 sq ft) through C-936 (936 sq ft) fits under the cap. Other municipalities publish a lower number, a percentage of the primary home, or no single cap. Setbacks and lot coverage still decide the parcel. Open your municipality page for the published figure.
Setbacks define how close an ADU can be placed to property lines. These vary by zone and municipality — and they’re what most often determine where on a lot an ADU can physically be placed.
ADU height limits typically range from 18 to 25 feet depending on the municipality and zone. Height matters for garage ADUs and any structure with a loft or second level.
ADUs typically require separate utility connections — water, sewer, and electrical. Connection capacity, tap fees, and access to existing lines all affect feasibility and cost. Wisconsin winters also require engineering decisions for water and drain lines.
Some municipalities require one off-street parking space per ADU. Others — including Madison in many districts — have reduced or eliminated this requirement. It depends on your parcel’s location and zone.
Find out what's buildable on your specific lot.
Zoning rules are a starting point — your lot size, setbacks, and existing structures all affect what's actually feasible. The free feasibility check gives you a definitive answer.
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