S1354 Allow Addition Of ADUs To Existing Properties

SUPPORT - Requires Idaho cities over 10,000 residents to allow Accessory Dwelling Units (ADUs)—one per lot—in single-family zones and limits both cities and HOAs from blocking them. The bill reduces barriers (parking, fees, owner-occupancy, size limits), requires by-right approval (must be approved if meets objective standards), and mandates zoning updates by Feb. 2027, while preserving health and safety standards.

This is a meaningful step toward improving affordability. By allowing smaller, lower-cost units in existing neighborhoods and removing common regulatory barriers, the bill makes it easier for homeowners to add rental housing or multigenerational living space. ADUs are typically among the most affordable forms of new housing, and this policy could expand supply relatively quickly. Compared to other reforms, ADU legalization is often one of the more effective tools for gradually increasing affordable housing options.

This legislation was signed into law on March 31, 2026.

See full bill here.