Side by side · Iowa
Compare ADU rules across Iowa
Flexible on where you build? The same backyard cottage can be routine in one city and impossible in the next. This table puts 20 Iowa cities side by side so you can shortlist the friendly ones before reading a single ordinance, or narrow it to just the cities you are deciding between. Every value is summarized from the city's own code; open a city's page for the full notes, citations, and fine print.
The short answers
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| City | Detached ADU | Attached / internal | Max size | Owner occupancy | Extra parking | Approval |
|---|---|---|---|---|---|---|
| Ames | Allowed | Allowed | 1,000 sq ft or 50% of the house's gross living area, whichever is larger (unfinished basements excluded); one bedroom; height, setbacks and coverage as for the house | Not required | None beyond the single-family requirement | Permitted use |
| Ankeny | Allowed | Allowed | 1,000 sq ft or 50 percent of the house, whichever is larger; height and setbacks follow the house's district rules | Not required | None beyond the single-family requirement | Permitted use |
| Bettendorf | Allowed | Allowed | At least 1,000 sq ft or 50 percent of the house's gross living area, whichever is larger (the local 400 to 800 sq ft range is void) | Not required | None beyond the single-family requirement (two spaces for the house) | Permitted use |
| Cedar Falls | Allowed | Allowed | 50 percent of the house's floor area (excluding an attached garage) or 1,000 sq ft, whichever is larger; 2 bedrooms max; minimum 125 sq ft; height no taller than the house's zone allowance | Not required | None beyond the single-family requirement (2 spaces per dwelling, plus 1 per adult beyond two in a rented house) | Permitted use |
| Cedar Rapids | Allowed | Allowed | 1,000 sq ft or 50% of the house's gross floor area, whichever is greater; height and setbacks follow the zone district's dwelling standards | Not required | None beyond the single-family requirement (state law); a leftover '1 per ADU' row in the city's parking table is void | Permitted use |
| Council Bluffs | Allowed | Allowed | At least 1,000 sq ft or 50% of the house's gross living area, whichever is larger (state floor; no local ADU cap); house height and setback rules apply (R-1: 35 ft, 25/5/20 ft setbacks) | Not required | None beyond the single-family requirement (2 spaces for a new house, 1 for a pre-existing one) | Permitted use |
| Davenport | Allowed | Allowed | At least 1,000 sq ft or 50% of the house's gross living area, whichever is larger (state floor; Davenport's flat 1,000 sq ft cap is void where 50% is larger); unfinished basements excluded | Not required | None beyond the single-family requirement | Permitted use |
| Des Moines | Allowed | Allowed | 1,000 sq ft or 50% of the principal house's floor area, whichever is larger; detached ADU height up to the principal building's maximum | Not required | None beyond the single-family requirement (1 space for the house) | Permitted use |
| Dickinson County | Allowed | Allowed | At least 1,000 sq ft or 50 percent of the house's gross living area, whichever is larger; house-level setbacks and 35 ft height | Not required | None beyond the single-family requirement | Permitted use |
| Dubuque | Allowed | Allowed | At least 1,000 sq ft or 50 percent of the house's gross living area, whichever is larger (state floor; unfinished basements excluded from the ADU's size from 7-1-2026); the local 600 sq ft / 50 percent of footprint cap is void | Not required | None beyond the single-family requirement (2 spaces per detached single-family dwelling); the local 1-space ADU rule is void | Permitted use |
| Iowa City | Allowed | Allowed | 1,000 sq ft or 50% of the house's floor area, whichever is larger (unfinished basements excluded); one ADU per lot | Not required | None beyond the single-family requirement | Permitted use |
| Marion | Allowed | Allowed | 1,000 sq ft or 50 percent of the house, whichever is larger (the state floor); unfinished basements excluded and the house measured by gross living area under SF 2369; same height, setbacks and bulk as a one-unit dwelling | Not required | None beyond the single-family requirement | Permitted use |
| Marshalltown | Allowed | Allowed | 1,000 sq ft or 50 percent of the house, whichever is larger; garage or workshop space outside the ADU not counted; setbacks same as the house | Not required | None beyond the single-family requirement | Permitted use |
| Mason City | Allowed | Allowed | At least 1,000 sq ft or 50 percent of the house's gross living area, whichever is larger (local text: 400 sq ft minimum; 1,000 sq ft or 50 percent of the house's gross ground floor area); height up to the house's limit (2 stories in Z1/Z2, 3 in Z3) | Not required | None beyond the single-family requirement | Permitted use |
| Polk County | Allowed | Allowed | At least 1,000 sq ft or 50 percent of the house's gross living area, whichever is larger (state floor); county text allows up to 1,200 sq ft gross floor area, excluding garage, porch and deck | Not required | None beyond the single-family requirement | Permitted use |
| Sioux City | Allowed | Allowed | At least 1,000 sq ft or 50 percent of the house's gross living area, whichever is larger (state floor); local caps of 600 sq ft detached and 25 percent of the house for integrated units are void | Not required | None beyond the single-family requirement (2 spaces per dwelling); the local extra-parking note is void | Permitted use |
| Urbandale | Allowed | Allowed | 1,000 sq ft or 50 percent of the primary dwelling, whichever is greater (the state floor); detached ADUs under 14 ft tall and 1,000 sq ft get a 10 ft rear setback | Not required | None beyond the single-family requirement | Permitted use |
| Waterloo | Allowed | Allowed | At least 1,000 sq ft or 50 percent of the house's gross living area, whichever is larger (state floor; Waterloo sets no ADU cap) | Not required | None beyond the single-family requirement (2 spaces for the house) | Permitted use |
| Waukee | Allowed | Allowed | At least 1,000 sq ft or 50 percent of the house's gross living area, whichever is larger; Waukee sets no larger cap | Not required | None beyond the single-family requirement | Permitted use |
| West Des Moines | Allowed | Allowed | 1,000 sq ft or 50 percent of the house, whichever is larger (the state floor, which the city code repeats) | Not required | None beyond the single-family requirement | Permitted use |
Summarized from each city's ordinance text, most recently read October 2026. Tap a value marked with an info icon to see exactly what it depends on, straight from the ordinance. Nearly every value has zone, lot-size, or process caveats beyond that; the per-city pages carry the full notes and code citations. Treat this as orientation, not a permit determination.
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Reading the table
- Detached ADU is the make-or-break column for backyard cottages: minimum lot sizes (often 8,000 to 14,500 sq ft) hide behind many of the "Allowed" values, so check your lot before celebrating.
- Attached / internal (basement apartments, additions) is legal almost everywhere and is usually the path of least resistance.
- Approval: "Permitted use" means staff-level sign-off; "Conditional use" means a public hearing, which adds time, cost, and uncertainty.
Ames: full rules and sourcesAnkeny: full rules and sourcesBettendorf: full rules and sourcesCedar Falls: full rules and sourcesCedar Rapids: full rules and sourcesCouncil Bluffs: full rules and sourcesDavenport: full rules and sourcesDes Moines: full rules and sourcesDickinson County: full rules and sourcesDubuque: full rules and sourcesIowa City: full rules and sourcesMarion: full rules and sourcesMarshalltown: full rules and sourcesMason City: full rules and sourcesPolk County: full rules and sourcesSioux City: full rules and sourcesUrbandale: full rules and sourcesWaterloo: full rules and sourcesWaukee: full rules and sourcesWest Des Moines: full rules and sources
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