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Bill Summary · SF 592

Summary — SF 592 (Signed into law May 1, 2025)

A bill to limit county and city regulation of accessory dwelling units (ADUs) and to require local governments to allow at least one ADU per single‑family lot.

Purpose

To expand housing options by ensuring counties and cities in Iowa must allow at least one accessory dwelling unit (ADU) on the same lot as a single‑family residence, to streamline permitting, and to restrict local regulations that would make ADU development more difficult than building or using the principal single‑family residence.

Key provisions

  • Applicability: Adds new subsections to county (Iowa Code §331.301) and city (Iowa Code §364.3) code chapters to require allowance of ADUs.
  • Minimum allowance: Each county and city must permit at least one ADU on the same lot as a single‑family residence.
  • Size limit: ADU may not exceed 1,000 square feet or 50% of the size of the single‑family residence, whichever is larger.
  • Building code: ADUs must comply with applicable building regulations (chapter 103A).
  • Permitted limits/exceptions: ADUs may only be prohibited or limited due to (a) adopted state historic building code restrictions, (b) deed restrictions, or (c) rules of a common interest community (HOA/condominium rules).
  • Manufactured/mobile homes: If used as an ADU, the unit must be placed on a permanent foundation and converted to real property and taxed under §435.26.
  • Preemptions — counties/cities may NOT impose requirements on ADUs that are more restrictive than those applied to single‑family residences, including:
    • Placement/appearance limits (heights, setbacks, lot size, frontage, lot coverage, density, aesthetic/architectural matching)
    • Additional parking requirements or fees in lieu of parking
    • Occupancy restrictions (owner‑occupancy, familial/employment relationships between occupants, income/age limits)
    • Special utility line requirements (except when separate metering cannot be provided)
    • Different impact fee structures or development standards vs. the single‑family residence on the same lot
    • Additional street/sidewalk improvement requirements beyond what's required for the single‑family residence
  • Permitting: ADU permit applications meeting statutory requirements must be approved without discretionary review or hearing and within the same timeframe used for single‑family residence approvals. Denials must be given in writing with reasons and remedies.
  • Conflicts: Any local ordinance, resolution, motion, or amendment that conflicts with these rules is void. Localities may adopt more permissive rules.

Definitions (selected)

  • “Accessory dwelling unit” — an additional residential dwelling unit on the same lot as a single‑family residence, attached or detached (including accessory structures like garages).
  • “Dwelling unit” and “single‑family residence” reference existing definitions in Iowa Code §562A.6.

Who is affected

  • Homeowners (can add an ADU subject to state limits)
  • Renters and prospective tenants (increased potential rental supply)
  • Local governments (reduced zoning/design discretion over ADUs)
  • Common interest communities (HOAs/condos) and deed‑restricted properties retain ability to limit ADUs per their rules
  • Owners of manufactured/mobile homes using them as ADUs (must convert to real property for taxation)

Procedural timeline / status

  • Introduced: March 10, 2025
  • Passed Senate: March 25, 2025 (49–0)
  • Passed House: April 8, 2025 (89–7)
  • Signed by Governor Kim Reynolds: May 1, 2025 — Enacted as Chapter 38.

Potential impacts / considerations

  • Likely to increase ADU construction and small‑scale rental/affordable housing options and support multigenerational housing.
  • Limits local zoning and design controls for ADUs—municipal and county planners will need to update ordinances and permitting practices.
  • HOAs and existing deed restrictions retain authority to limit ADUs.
  • Tax and utility implications for units converted from manufactured/mobile homes (conversion to real property and tax assessment).

Compiled from official sources — confirm details with the bill’s official record.

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