Senate File 592

Senate File 592 (SF 592), enacted by the Iowa Legislature in 2025, mandates that cities and counties permit at least one accessory dwelling unit (ADU) on residential lots. This legislation aims to increase housing availability and affordability by facilitating the construction of secondary housing units, such as backyard cottages or garage apartments.

Key Provisions:

• Mandatory ADU Allowance: Local governments must allow at least one ADU on residential lots, overriding local zoning restrictions that previously prohibited them.

• Effective Date: The law takes effect on July 1, 2025.

The bill was signed into law by the Governor on May 1, 2025, after passing both legislative chambers with substantial support.

This legislation is part of a broader effort to address housing shortages and promote diverse housing options across Iowa.

**Always work with your local government to obtain the required permits**

https://www.legis.iowa.gov/legislation/BillBook?ga=91&ba=SF%20592

Quick Summary: (contact your local officials for information pertaining to your specific questions/needs.)

Accessory Dwelling Unit (ADU) Guidelines – SF 592

• One ADU per Lot: Cities and counties must allow at least one ADU on each residentially zoned lot that contains a single-family home.

• Detached, Attached, or Internal: ADUs may be:

  • Detached units (e.g., backyard cottage, tiny home).

  • Attached units (e.g., addition connected to the main home).

  • Interior conversions (e.g., basement or attic apartments).

• No Owner-Occupancy Requirement: The law prohibits cities/counties from requiring the primary home or ADU to be owner-occupied.

• No Additional Parking Requirement: Jurisdictions cannot mandate extra off-street parking solely because of an ADU.

• Size and Design Flexibility: While local governments can establish reasonable regulations (e.g., height limits, setbacks, and lot coverage), they cannot impose:

  • Minimum lot size requirements beyond what exists for single-family homes.

  • Restrictions that effectively prevent ADUs.

• Efficient Permitting: Cities and counties are encouraged to streamline the permitting process to facilitate ADU construction.

This legislation, effective July 1, 2025, mandates that cities and counties in Iowa must allow at least one Accessory Dwelling Unit (ADU) on residential lots containing a single-family home. Below are the specific provisions detailing what can be built:

Key Provisions of SF 592

1. Mandatory ADU Allowance

• Requirement: Cities and counties must permit at least one ADU on the same lot as a single-family residence.

2. ADU Size and Type

• Maximum Size: An ADU must not exceed 1,000 square feet or 50% of the size of the primary residence, whichever is larger.

• Types Permitted:

  • Detached Units: Standalone structures, such as backyard cottages.

  • Attached Units: Additions connected to the main home.

  • Interior Conversions: Basement or attic apartments.

3. Design and Aesthetic Regulations

• Restrictions Prohibited: Local governments cannot impose design standards on ADUs that are more restrictive than those applied to single-family residences. This includes:

  • Maximum building heights

  • Minimum setback requirements

  • Minimum lot sizes

  • Minimum building frontages

  • Maximum lot coverages

  • Density requirements

  • Aesthetic or architectural standards

• Matching Requirements: ADUs are not required to match the exterior design, roof pitch, or finishing materials of the primary residence.

4. Occupancy and Use

• Occupancy Restrictions: Local governments cannot:

  • Require the property owner to reside on the property.

  • Mandate familial, marital, or employment relationships between occupants of the primary residence and the ADU.

  • Restrict occupancy based on income or age.

• Rental Use: ADUs can be used as rental properties, and regulations cannot be more restrictive than those applied to single-family residences.

5. Parking and Utilities

• Parking: No additional off-street parking requirements can be imposed solely due to the presence of an ADU.

• Utilities:

  • Local governments cannot require new or separate utility lines between the ADU and public utility service connections.

  • However, if full utility access, including separate metering for billing purposes, cannot be provided, then new or separate utility lines may be required.

6. Permitting Process

• Approval Timeline: ADU permit applications must be approved without discretionary review or hearing and within the same timeframe as single-family residence applications.

• Denial Protocol: If a permit is denied, the applicant must receive a written explanation, including any remedies necessary to secure approval.

7. Preemption of Conflicting Regulations

• Local Ordinances: Any local ordinances, motions, resolutions, or amendments that conflict with these provisions are considered void.

• More Permissive Regulations: Local governments may adopt regulations that are more permissive than the state requirements.

This legislation aims to streamline the development of ADUs across Iowa, promoting increased housing availability and affordability.