City Council revises accessory dwelling unit regulations to align with new state law

In a pivotal meeting held on June 9, 2025, the Ames City Historic Preservation Commission discussed significant changes to the regulations surrounding accessory dwelling units (ADUs) in response to new state legislation. The atmosphere in the room was charged with urgency as city officials prepared to align local codes with the state’s mandate, which takes effect on July 1.

The new state law aims to simplify the process for homeowners wishing to add ADUs—small units designed to be placed on single-family lots. Under the revised regulations, these units cannot exceed 1,000 square feet or 50% of the size of the primary home. Notably, the law stipulates that ADUs must be treated similarly to single-family homes in terms of height, setbacks, and density, eliminating previous local restrictions that required them to match the exterior design of the main house.

One of the most significant shifts is the removal of rental restrictions. Previously, homeowners could only rent out an ADU if they lived on the property. This change opens the door for homeowners to potentially use ADUs as rental properties, including short-term rentals like Airbnbs, which could lead to a rise in rental opportunities within the community.

The commission also discussed the implications of these changes on historic preservation. While the new regulations will allow for more flexibility in ADU construction, they will still require adherence to historic guidelines during the design review process. This means that any new ADU, whether attached or detached, will need to be evaluated for its impact on the historic character of the neighborhood.

As the meeting progressed, council members expressed concerns about the potential increase in density and the preservation of the city’s historic charm. The commission clarified that while ADUs can now be built on properties with duplexes, they will not be permitted on lots with multi-family apartment buildings, maintaining a level of control over where these units can be placed.

The urgency of the meeting was underscored by the tight timeline for implementing these changes. With only two months to revise local codes, the commission is racing against the clock to ensure compliance with state law while balancing the needs of the community and the preservation of Ames’ historic character.

In a unanimous vote, the commission adopted the proposed changes, setting the stage for a new era of housing options in Ames. As the city moves forward, residents will be watching closely to see how these new regulations will shape their neighborhoods and the future of housing in Ames.