ADU rules in Council Bluffs

Council Bluffs's zoning title never mentions accessory dwelling units: the residential accessory-use list in §15.24.020 covers garages, sheds, pools, greenhouses and similar structures but no dwelling, and §15.24.020 and the R-1 rules allow 'only one principal structure or use' per lot. The city has not amended Title 15 for SF 592, so the operative rule is the state floor: Iowa Code §364.3(23)(a) requires every city to allow at least one ADU on the same lot as a single-family residence, expressly including one 'part of an accessory structure such as a detached garage', and (d) voids any conflicting city text. A detached backyard unit or garage apartment is therefore allowed on any lot with a single-family house, built to the city's adopted building code.

The state definition covers a unit 'either attached to or detached from the single family residence', so a basement, attic or addition apartment is allowed alongside the house. Locally, the zoning code defines a single-family detached dwelling as 'A building containing only one dwelling unit' (§15.03.230), which on its own would bar a second unit inside the house; that definition is void to the extent it conflicts with §364.3(23). Since 7-1-2026 SF 2369 requires the ADU to be allowed in any zoning district where a single-family residence is an allowed principal use.

The city sets no ADU size of its own, so the cap is the state minimum: the city must allow up to 'one thousand square feet or fifty percent of the size of the single family residence, whichever is larger'. Under SF 2369 (effective 7-1-2026) 'size' is the house's gross living area excluding garages, decks and unheated porches, and unfinished basements are excluded from the ADU calculation. Because placement rules may not be stricter than those for the house, a detached ADU is held to the principal-structure standards (in R-1, 35 ft height, 25 ft front, 5 ft or 10 percent side, 20 ft rear, 35 percent total lot coverage) rather than the 18 ft accessory-structure height. The R-1 rule that 'No accessory structure shall exceed the ground floor coverage of the principal structure' cannot cut an ADU below the state minimum.

Nothing in the Council Bluffs code requires the owner to live on a lot with an ADU, and Iowa Code §364.3(23)(b)(4) forbids any city restriction 'requiring the property owner to be a resident', a family or employment relationship between the occupants, or income or age limits. Both the house and the ADU may be occupied by tenants.

The parking table in §15.23.060 has no ADU row; it requires 2 spaces per single-family dwelling (1 per dwelling for single-family homes existing before the parking chapter took effect). Iowa Code §364.3(23)(b)(3) bars any requirement for 'additional parking beyond that required for a single family residence or payment of a fee in lieu', so an ADU adds no space even though the city's two-family and multifamily rows would otherwise count units.

Iowa Code §364.3(23)(c) requires the city to approve a compliant ADU application 'without discretionary review or hearing' and on the same timeline as a single-family residence, with any denial in writing. Council Bluffs has no ADU-specific procedure, so in practice an ADU goes through ordinary building permits from the Building Department; §15.02.100 exempts single-family dwellings from the separate zoning certificate. No conditional use or Zoning Board of Adjustment hearing may be required, although a landmark or locally designated historic district property still needs the Title 16 certificate of appropriateness for exterior work.

Every owner of rental property must register each rental dwelling unit with the building official every year (§17.09.020), and 'It is a violation of this code for an owner or operator to allow anyone to rent or occupy any rental property unless the owner or operator holds a valid rental registration and certificate of compliance' (§17.09.035); units are inspected every one to three years. These rules apply to all rentals, so they lawfully reach an ADU under §364.3(23)(b)(2). The code has no short-term rental licence or zoning rule, and Iowa Code §414.1(1)(e) bars any city regulation 'relating to short-term rental properties', classifies them as residential use and forbids a short-term-rental licence or permit fee; nightly rentals remain subject to the city's 7 percent hotel and motel tax (ch. 2.04) and general nuisance and safety rules.