Dane County, WI Accessory Structures: ADU Rules (2026)
ADU rules in Dane County, WI, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- Permitted Districts
- Residential and some agricultural zones
- Owner-Occupancy
- Verify current Chapter 10 requirements
- Separate Sale
- Not permitted
- Permit Required
- Yes
Summary
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.
(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 dwelling units shall not be sold separately from the principal dwelling unit, nor from the property on which it sits. (h) A lot or parcel of land containing an accessory dwelling unit shall be occupied by the owner of the premises. The owner may live in either the accessory dwelling unit or the principal residence. (j) Off-street parking shall be provided consistent with s. 10.102(8). (k) Accessory dwelling units must meet applicable residential building codes and sanitary codes.
Full Breakdown
Dane County Chapter 10 permits accessory dwelling units in residential and some agricultural zoning districts. ADUs are permitted as an accessory use to the principal dwelling. They must remain on the same lot as the principal structure and cannot be subdivided or sold independently. Size and height standards are subordinate to the principal dwelling. A building permit and zoning compliance review are required. Dane County has been generally supportive of ADUs as part of county housing strategy.
Violations & Fines
ADUs built without permits or that violate zoning standards are subject to Dane County enforcement, including stop-work orders and fines.
Frequently Asked Questions
Can I build a guest house or in-law suite in rural Dane County?
Can I sell a Dane County ADU separately from the main house?
Does Dane County require the ADU owner to live on site?
Sources & Official References
Other rules in Dane County
How Dane County compares: Easiest Cities to Build an ADU·Compare Dane County to another location·View the Wisconsin accessory structures overview
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