Ashwaubenon, WI Accessory Structures: ADU Rules (2026)

Chapter 17 of the Ashwaubenon Code is the Zoning Ordinance, adopted under Wis. Stat. Sec. 61.35 and Sec. 62.23. 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. 17-5-100 Table of Dimensional Standards in Residential Districts (Notes) states that minimum residential floor areas 'do not apply to accessory dwelling units.' 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.