Accessory Structures in Dane County, WI (2026)
3 county-level rules, plus city-specific rules for 4 cities in Dane County, Wisconsin.
Verified from official government sources
ADU Rules
ADUs in unincorporated Dane County are permitted in appropriate zoning districts under Chapter 10. ADUs must be accessory to the principal dwelling and cannot be sold separately.
Dane County ADU / Accessory Dwelling Rules
Some RestrictionsDane County Code of Ordinances, ch. 10.103(1)(c)-(k) (Accessory dwelling units)
(c) A detached accessory dwelling unit may be included in either an existing or new dwelling unit. (d) Lots accommodating an accessory dwelling unit must meet the minimum lot size for the applicable zoning district. (e) In no case shall an accessory dwelling unit exceed 800 square feet of occupiable floor area. (f) No accessory dwelling unit shall have more than two bedrooms. (g) Accessory dwel...
Shed & Carport Rules
A shed of 120 square feet or less on a non-permanent foundation needs no zoning permit in unincorporated Dane County, as long as it still meets setback, height and lot coverage rules. In the SFR-08 district, larger accessory buildings top out at 12 feet, sit at least 10 feet off the rear line, and can't exceed the footprint of the house.
Dane County Shed & Accessory Building Rules
Some RestrictionsDane County Code of Ordinances, ch. 10.101(1)(b); ch. 10.251(5)(c)3.-4., (6)(b), (7)(b)
(b) Exceptions. Zoning permits under this chapter are not required for accessory buildings equal to or less than 120 square feet on non-permanent foundations, provided they meet all setback, height, and lot coverage requirements. ... (5) Setbacks and required yards. ... (c) Rear yard. ... 3. Except as exempted in 4 below, accessory buildings must be at least 10 feet from the rear lot line. 4. A...
Garage Conversions
Dane County's zoning code flatly bars turning a garage or other accessory building into living space. Section 10.004(2) defines an accessory building as incidental to the main building and states that, except for accessory dwelling units, accessory buildings may not be used for human habitation. The rule applies only in unincorporated towns that adopted county zoning, not inside Madison or the county's cities and villages.
Dane County Garage Conversion to Living Space Rules
Significant RestrictionsDane County Code of Ordinances, ch. 10.004(2), (4)(b)
(2) Accessory building. A subordinate or supplemental building, the use of which is incidental to that of the main building on the same lot or the use of the premises on which it is located. Except for accessory dwelling units, accessory buildings may not be used for human habitation. ... (4) Accessory dwelling unit - detached. ... (b) This definition includes accessory buildings constructed in...
Accessory Structures by City in Dane County
4 cities in Dane County have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.
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