Iowa Lawmakers Clarify Rules for Accessory Dwelling Units

As communities across Iowa continue exploring solutions to housing supply and affordability challenges, lawmakers revisited accessory dwelling unit (ADU) policy during the 2026 legislative session.

Building on legislation passed last year requiring local governments to allow at least one ADU in single-family zoning districts, SF2629 provides additional guidance and clarification on how those rules should be applied.

SF2629 affirms that a county shall allow a minimum of one accessory dwelling unit on the same lot as a single family residence within a zoning district where a single family residence is an allowed principal use while clarifying that counties may only restrict ADUs in historic preservation districts if the historic preservation commission finds the proposed unit would negatively impact the historical or cultural character of the area, and the commission must formally record its reasoning. 

Additionally, the bill defines “size” for regulatory purposes as the home’s gross living area, not counting garages, decks, or unheated porches, and clarifies that when determining the maximum size of an ADU, unfinished basements are not counted in the calculation.

Check out these other important updates on the Iowa REALTORS® 2026 Legislative wins related to Property Tax Reform and HOA Transparency/Home Inspector Clarifications, as well as a look at what we're keeping an eye on for 2027.