Polk County, IA Accessory Structures: Tiny Homes (2026)

Article 4, Division 4, Section 2(F) of the Polk County Zoning Ordinance sets up the county's accessory dwelling unit program to house family members, elderly relatives, students, in-home health care providers and people with disabilities on existing legal lots, but subsection (F)(6) draws a hard line against using a standalone structure as that unit: a stick-built house, manufactured home, single-wide mobile home, travel trailer, recreational vehicle, tiny home, or any other temporary or portable structure cannot be permitted as an ADU. The only path to a legal second unit under (F)(2) is a unit built into or attached to the primary dwelling, or attached to or integrated within a permanent accessory building, capped at 1,200 square feet of gross floor area and no larger than the existing principal residence; an ADU placed inside an accessory building can take up no more than 50% of that structure's footprint.

Subsection (F)(12) closes an obvious workaround by barring a nonconforming accessory structure from being renovated or reconstructed into an ADU, so a tiny home already sitting on a lot as an accessory building cannot be converted into a permitted dwelling unit either. A landowner who wants extra living space for a family member has to build within or attach to an existing structure and go through the county's ADU permitting process with Public Works Planning and Development rather than placing a manufactured tiny house on a separate foundation.