Accessory Structures in Winnebago County, WI (2026)
4 county-level rules, plus city-specific rules for 1 city in Winnebago County, Wisconsin.
Verified from official government sources
ADU Rules
Winnebago County zoning allows a mother-in-law suite as an accessory use only if it sits entirely inside the principal structure and isn't recognizable from outside as a separate dwelling: no separate address, meter, or entrance.
Winnebago County Mother-In-Law Suite Rules
Some RestrictionsWinnebago County Code Ch. 23, Art. 8 § 23.8-474 (Mother-in-law suite)
The residential quarters must be contained entirely within the principal structure and shall not be recognizable from the outside as a separate dwelling unit utilizing such characteristics as a separate address, separate utility meter, or a separate entrance which is the sole means of entry into the unit. (a)Accessory floor area. A mother-in-law suite is exempt from counting towar...
ADU Owner Occupancy
Winnebago County zoning defines a mother-in-law suite as quarters accessory to, and used by, immediate relatives of the household in the principal residence, not an independently rentable unit.
Winnebago County ADU Relative-Only Rule
Some RestrictionsWinnebago County Code Ch. 23, Art. 3 § 17.34 (definition, applied through § 23.8-474)
17.34 Mother-in-law-suite Residential quarters accessory to, but contained entirely within, the principal residence and used by immediate relatives.
ADU Rental Restrictions
Winnebago County bars a mother-in-law suite from having its own address, utility meter, or separate entrance: the features that would let it function as an independently rented unit.
Winnebago County ADU Rental Restrictions
Significant RestrictionsWinnebago County Code Ch. 23 § 23.8-474 (Mother-in-law suite)
The residential quarters must be contained entirely within the principal structure and shall not be recognizable from the outside as a separate dwelling unit utilizing such characteristics as a separate address, separate utility meter, or a separate entrance which is the sole means of entry into the unit. (a)Accessory floor area. A mother-in-law suite is exempt from counting towar...
Shed & Carport Rules
A carport counts as a residential garage under Chapter 23's town/county zoning, so it needs a zoning permit and must be conventional wood-frame, metal-frame, or masonry construction: soft-sided canopy carports are barred outright in every zoning district.
Winnebago County Carport Construction Rules
Some RestrictionsWinnebago County Code Ch. 23 §§ 17.20, 23.8-460 (Town/County Zoning)
A residential garage may be detached or attached to a building with a residential use. A carport shall be considered to be a residential garage. ... (a) Location. A garage may be attached to the residence or detached. (b) Type of construction. A garage shall be of conventional wood-frame, metal-frame, or masonry construction. Soft-sided structures and canopies are specifically prohibited.
Accessory Structures by City in Winnebago County
1 cities in Winnebago County have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.
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