Milton, WI Accessory Structures: ADU Rules (2026)

The City of Milton, Rock County, Wisconsin zoning ordinance defines an accessory dwelling unit (ADU) as a second, independently habitable residence on the same lot as a single-family home, either attached or in a detached building, per Sec. 28(1). Backyard cottages, garage apartments, and basement units all qualify as long as each includes its own kitchen, bathroom, heating and sanitation facilities, meeting the code's 'independently habitable' standard. The code sets a hard cap of 750 square feet for any ADU sharing a lot with a single-family dwelling.

Before construction or occupancy, either the principal dwelling or the ADU itself must be owner-occupied as the property owner's primary residence, and the owner must record a restrictive agreement with the city confirming that condition before the zoning permit is issued. The ADU cannot be sold or conveyed separately from the principal home, keeping the two under one deed. New entrances may open onto the side, rear or street-side elevation, but not the front, and any entry in a side, rear or street-side yard must connect to the street by a paved walkway or driveway.

The ADU must otherwise meet the setbacks and dimensional standards of the underlying zoning district. Off-street parking is waived only if on-street parking already exists adjacent to the property, as determined by the zoning administrator; otherwise the residential parking table in Sec. 06 applies. A zoning permit under Sec. 41 is required before any ADU is established, and the appearance of the principal building cannot be significantly altered so it no longer reads as a single-family home.