Dubuque, IA Accessory Structures: ADU Rules (2026)

Because an accessory dwelling unit is listed as a conditional use under section 16-8-5-10 of the Unified Development Code, a property owner must first obtain a conditional use permit from the Dubuque Zoning Board of Adjustment before building or converting one, rather than simply pulling a building permit. The ordinance limits the use to one accessory unit per zoning lot, and only within the R-1, R-2, R-2A, R-3, R-4, OR, OC and C-1 districts; it is not a permitted use in other commercial, industrial or manufactured-home districts.

Eligibility hinges on the principal structure: the main dwelling must be a single-family detached house, either the principal dwelling or the accessory unit must be owner-occupied, and the accessory unit must remain incidental and subordinate to the principal dwelling rather than a co-equal use. Size is capped at whichever is smaller, fifty percent (50%) of the principal dwelling's building footprint or six hundred (600) total gross square feet, and the unit must otherwise meet the bulk regulations (setbacks, height, coverage) that apply to its own zoning district.

Because it is meant to function as an independent living facility, the unit must comply with the city's housing, fire and building codes and include its own separate entrance, cooking facilities, eating area, sanitation and sleeping space, plus one off-street parking space. Under section 16-8-5-7, a granted conditional use permit expires after two years unless a building permit is obtained and construction started, or an occupancy permit is obtained and the use begun, though the zoning board may grant one extension of up to six months on written application.

Violating any condition attached to the permit is treated under section 16-8-5-5(C) as a violation of Title 16 itself, exposing the owner to the same enforcement and penalty provisions as any other zoning violation.