IA HF2252

Counties and cities must allow at least one accessory dwelling unit (ADU) on any lot with a single-family residence in zoning districts where single-family homes are permitted as a principal use.

ADUs cannot exceed 1,000 square feet or 50% of the primary residence's gross living area (excluding garages, decks, and unheated porches), whichever is larger; unfinished basements are excluded from size calculations.

ADUs may only be prohibited or limited by state historic building code restrictions, deed restrictions, or rules of common interest communities (HOAs); local regulations cannot be more restrictive for common interest communities than for standard single-family residences.

Manufactured or mobile homes used as ADUs must be converted to real property by placement on a permanent foundation and assessed for real estate taxes.

Historic preservation districts and areas of historical significance may regulate ADUs only if the reviewing commission determines the proposed unit would be incongruous with the historical, architectural, archaeological, or cultural character of the area, with documented reasons.