Ames, IA Accessory Structures: Garage Conversions (2026)

Ames Municipal Code Section 31.11(1)(a) splits Certificate of Appropriateness review into two tracks within a designated historic district. Ordinary alterations to a principal structure, garage or other accessory building, and new fences or retaining walls, can be approved administratively by the Planning and Housing Director, provided the work meets the adopted Design Guidelines and Design Criteria and does not use substitute materials outside those specifically listed. Converting a contributing garage into an Accessory Dwelling Unit is carved out of that administrative track: it requires approval from the Historic Preservation Commission itself, and the Director retains discretion to refer any other alteration application to the Commission as well.

Section 31.10(6) separately governs demolishing a contributing garage rather than converting it, requiring the Commission to weigh historical significance, architectural integrity, functionality, structural condition and site location before allowing demolition, and noting that a garage too small for modern vehicles can still be repurposed rather than torn down. Once granted, a Certificate of Appropriateness for a garage conversion is effective for one year from Commission approval under Section 31.11(5), though the Planning and Housing Director may approve a one-year extension if the applicable codes have not changed. Every property that has once obtained a Certificate of Appropriateness must obtain a new one for any later alteration, new construction or demolition.