Middleton, WI Accessory Structures: ADU Rules (2026)

28(1) defines an ADU as a second independently habitable unit, including one above a ground-floor office or commercial use, or one on the same lot as a single- or two-family dwelling, attached or detached; a manufactured home may serve as the unit. The number of occupants is capped at one family, and new entrances cannot be added to the front elevation, only the side, rear, or street side. 05(3). ADUs on the same lot as a single- or two-family home carry four added conditions: either the principal building or the ADU must be the owner's primary residence for at least ten months of the calendar year, backed by a restrictive agreement recorded with the City before a zoning permit issues; the ADU cannot be sold, conveyed, or titled separately from the principal dwelling; its floor area cannot exceed that of the principal dwelling; and the building's exterior appearance must still read as a single- or two-family home.

No off-street parking is required for an ADU, and the City waives both park-fee-in-lieu and park improvement fees for an ADU permit. 41 is mandatory before establishing any ADU, and that review is decided in writing within 30 days, with work required to start within 365 days and finish within 730 days.