Ashwaubenon, WI Accessory Structures: ADU Rules (2026)
ADU rules in Ashwaubenon, WI, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- ADU Status
- Sec. 17-3-200 defines Accessory Dwelling Unit as a secondary dwelling subordinate to a principal dwelling, attached or detached on the same lot
- Permitted Zones
- Residential districts: R-1 One-Family, RE Rural Estate, R-2 Two-Family, R-3 Multiple-Family
- ADU Status
- ADUs are not listed in the Sec. 17-4-200 Household Living Use Types
- Floor Area
- Sec. 17-4-400 caps accessory-building floor area at 576/768/936 sq ft based on lot size in R-1 and R-2
- Height
- Maximum accessory-building height is 15 feet in R-1 and R-2
- ADU Status
- Sec. 17-5-100 Table of Dimensional Standards exempts ADUs from minimum residential floor-area requirements
- Requirement
- Zoning authority is Wis. Stat. Sec. 61.35 and Sec. 62.23
Summary
The Village of Ashwaubenon defines an Accessory Dwelling Unit in Sec. 17-3-200 of the Zoning Code (Chapter 17) as 'a secondary dwelling unit established in conjunction with and clearly subordinate to a principal dwelling unit, whether part of the same structure as the principal dwelling unit, or as a detached structure on the same lot.' The Zoning Code is adopted under Wis. Stat. Sec. 61.35 (village zoning) and Sec. 62.23. ADUs are not listed as a Use Type in the Sec. 17-4-200 Household Living category (which lists single-family detached, single-family attached, two-family, townhouses, and multifamily). The Sec. 17-5-100 Table of Dimensional Standards in Residential Districts notes that the residential floor-area minimums 'do not apply to accessory dwelling units.' Residential districts are R-1 (One-Family), RE (Rural Estate), R-2 (Two-Family), and R-3 (Multiple-Family).
ACCESSORY DWELLING UNIT. A secondary dwelling unit established in conjunction with and clearly subordinate to a principal dwelling unit, whether part of the same structure as the principal dwelling unit, or as a detached structure on the same lot. ACCESSORY BUILDING. A building, the use of which clearly is subordinate to and incidental to the use of the main building on the same lot. [TABLE 17-5-200 (5): MINIMUM HOUSE SIZE - NOTES:] [1] The floor area requirement excludes porches and garages. [2] These standards do not apply to accessory dwelling units.
Full Breakdown
Chapter 17 of the Ashwaubenon Code is the Zoning Ordinance, adopted under Wis. Stat. Sec. 35 and Sec. 23. Sec. 17-3-200 defines 'Accessory Dwelling Unit' as a secondary dwelling unit subordinate to a principal dwelling, attached or detached on the same lot, and 'Accessory Building' as a building subordinate and incidental to the main building. The Sec. 17-4-100 Table of Allowable Uses governs which uses are permitted in each district; Household Living Use Types listed under Sec. 17-4-200(A)(1) are single-family detached, single-family attached, two-family, townhouses, multiple-family, live/work, and upper-story dwellings.
Sec. 17-4-400 sets accessory-structure standards: in R-1 and R-2 districts, total accessory-building floor area is capped at 576 sq ft on lots under 15,000 sq ft, 768 sq ft on lots 15,000-25,000 sq ft, and 936 sq ft on lots over 25,000 sq ft, with a 15-foot maximum height and 6-foot rear and side setbacks (4-foot side without a 2-car attached garage). Sec. 17-4-400(D)(2) requires every single-family and two-family dwelling to have a private garage at least 12 by 22 feet. The Sec. ' Sec.
17-3-200 also defines Zero Lot Line Duplex (a two-family dwelling with units on separate lots), permitted under Sec. 17-5-100(F)(2). Because ADUs are not enumerated as a permitted Household Living Use Type, applicants should confirm with the Community Development Department (920-593-4405) and the Sec. 17-4-100(B) rule that uses not listed are prohibited.
Violations & Fines
Constructing an accessory building or dwelling without a permit, or in violation of size, height, or setback limits in Sec. 17-4-400, is a Chapter 17 violation. Sec. 17-9-200 makes any non-conforming construction null and void and authorizes the Village Attorney to seek injunction, mandamus, abatement, or removal, with forfeitures under the Sec. 1-1-13 bond schedule of the Village Municipal Court. Use of a structure for human habitation that is not a permitted Household Living Use Type in the applicable district is independently a Chapter 17 violation.
Frequently Asked Questions
Are accessory dwelling units allowed in Ashwaubenon, WI?
How big can an accessory building be in Ashwaubenon's R-1 or R-2 district?
Does Ashwaubenon's minimum floor-area standard apply to an ADU?
Sources & Official References
Other rules in Ashwaubenon
How Ashwaubenon compares: Easiest Cities to Build an ADU·Compare Ashwaubenon to another location·View the Wisconsin accessory structures overview
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