ADU Design in Hales Corners, WI

ADU Design in Wisconsin: what governs your project

Wisconsin has no statewide ADU statute; ADUs are governed by each municipality's zoning ordinance. Madison and Milwaukee have adopted ADU-friendly provisions, but standards vary widely across the state's cities and villages.

Energy code

Permitting varies by jurisdiction: typical local rules cap ADU size relative to the primary home, set parking and setback requirements, and use standard residential permits. Winter foundation and frost-depth requirements follow the state building code.

Permitting & plan check

The Department of Safety and Professional Services reviews commercial building plans at the state level for many municipalities, while larger cities operate delegated plan review programs. Building permits are issued locally under the Wisconsin Commercial Building Code. Designers should verify whether a project falls under state or delegated municipal review early in the process.

Good to know

• Wisconsin's frost penetration runs deep, so building foundations and footings must extend well below grade to get beneath the frost line.
• Northern and lake-effect regions of Wisconsin see some of the heaviest snow loads in the Midwest, making roof snow design a controlling case.
• Wisconsin's commercial building plan review is handled at the state level by the Department of Safety and Professional Services for many project types.

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