Oshkosh, WI Accessory Structures: ADU Rules (2026)

Oshkosh's Chapter 30 Zoning Ordinance is organized by articles (Article III Land Use Regulations, Article IV Bulk Regulations, Article VI Overlay Zoning Districts, etc.) and adopted under the city zoning authority granted by Wis. Stat. Sec. 62.23. The city's published Land Use Tables list permitted, conditional, and special uses by base zoning district. Single-Family Detached, Two-Family, and Multi-Family Dwellings are listed as separate residential land uses; an 'Accessory Dwelling Unit' or 'Junior ADU' is not a stand-alone use category in the current published tables. Practical implications: (1) on a single-family-zoned lot, a second independent kitchen/bathroom/sleeping unit is typically only allowed where the district permits a two-family dwelling and the lot meets bulk standards (lot area, width, setbacks) in Article IV; (2) detached accessory buildings are regulated as accessory structures under Article III and are limited in height, area, lot coverage, and setback - habitable independent dwelling space inside an accessory building is not a default permitted accessory use; (3) interior conversions creating a second dwelling unit require both zoning approval and building permits issued through the Inspection Services Division (Chapter 7 Building Code). Because the city has expressed interest in workforce housing flexibility (including reducing minimum dwelling size to 400 sq ft), homeowners should confirm current code text and any pending amendments with Planning Services at 215 Church Avenue, Room 204, before designing or permitting a second unit. State enabling law for any future ADU ordinance would still flow from Wis. Stat. Sec. 62.23.