Iowa ADU Rules Law: Statewide Accessory Structures Rules (2026)

Iowa Statewide ADU Law Preempts Local Bans

Few RestrictionsApplies statewide across Iowa (2026)

Senate File 592, effective July 1, 2025, requires every Iowa city and county to allow at least one accessory dwelling unit on any lot with a single-family residence. Local governments cannot ban ADUs or impose more restrictive standards than apply to the primary house.

Key Facts

Statute: Senate File 592 (2025)
Effective date: July 1, 2025
Maximum size: 1,000 sq ft or 50%
Building code: Iowa Code Ch. 103A
Applies to: All cities and counties

Full Breakdown

SF 592 amended Iowa Code Chapters 414 (city zoning) and 335 (county zoning) to mandate ADU approval statewide. ADUs may not exceed the greater of 1,000 square feet or 50% of the primary residence and must comply with the State Building Code (Chapter 103A). Cities and counties cannot impose stricter setback, height, lot size, frontage, lot coverage, density, or aesthetic standards on ADUs than on the primary home. Localities cannot add parking requirements, separate utility line requirements (with limited exceptions), or different impact fees. Owner-occupancy mandates and short-term rental bans tied to ADUs are also preempted.

Violations & Penalties

Local ADU prohibitions, owner-occupancy requirements, separate impact fees, or stricter dimensional standards adopted after July 1, 2025, are unenforceable. Aggrieved property owners may seek judicial review or declaratory relief.

Frequently Asked Questions

Can my Iowa city still prohibit ADUs?

No. As of July 1, 2025, every Iowa city and county must allow at least one ADU on lots with a single-family home. Local outright bans are preempted by Senate File 592.

Can the city require me to live on-site or restrict renting the ADU?

No. SF 592 prohibits owner-occupancy mandates and bars cities from imposing rental restrictions on ADUs that are more restrictive than for any other rental property.

What standards still apply to ADU construction?

ADUs must comply with the Iowa State Building Code, deed restrictions, historic district rules, and reasonable safety standards. Same setback and dimensional rules as the primary house apply.