Dane County, WI Accessory Structures: Garage Conversions (2026)

The prohibition lives in the zoning ordinance's definitions section, not a standalone garage rule: Sec. 004(2) defines "accessory building" as "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," then adds the human-habitation bar. A detached garage is squarely an accessory building, so finishing one into a bedroom, kitchen or full living unit without more is a code violation. The only lawful path is the accessory dwelling unit route: Sec.

004(4)(b) specifically recognizes "accessory buildings constructed in connection with a private garage or a private garage converted into a dwelling unit" as a detached accessory dwelling unit, which then must clear the county's separate ADU permitting standards under ch. 103 before anyone can live in the converted space. Occupancy itself is gated separately: Sec. 101(5)(a) bars using any building or addition, accessory buildings included, until a certificate of compliance is issued by the county zoning administrator, so a homeowner can't just move furniture into a converted garage before sign-off.

Enforcement runs through the zoning administrator's citation authority under Sec. 101(4)(c) and the forfeiture schedule in Sec. 101(4)(d), and Sec. 101(4)(a)1 makes every day the violation continues a separate offense. This chapter only reaches unincorporated towns that opted into Dane County zoning; Madison, Sun Prairie, Fitchburg, Middleton, Verona, Stoughton and Monona each enforce their own municipal codes for garage conversions instead.