Johnson County, IA Historic Preservation: Historic-Cultural Monuments (2026)

5(E) of the Unified Development Ordinance treats Historic Properties as a Sensitive Area, defined to include structures over one hundred years old with architectural or historical significance and significant archaeological sites. Before development, an applicant must identify whether either exists: structures a century or older trigger review by a qualified architectural historian, who decides whether a full architectural history survey is warranted following the Iowa Site Inventory Form process used by the State Historic Preservation Office, and archaeological review requires a Site Search through the University of Iowa Office of the State Archaeologist (OSA), with any recommended survey completed under AIA guidelines and National Register Bulletin #15 significance standards.

5(E)(2) requires the applicant to establish a buffer zone of at least 50 feet around the property, though the Zoning Administrator has discretion to allow buffer averaging, with OSA consultation required first for archaeological sites. Within that buffer, the historic property must be left undisturbed except for non-invasive upkeep such as mowing, noxious-weed removal, and basic maintenance to preserve a standing structure's integrity, unless the applicant demonstrates that leaving it undisturbed is unreasonable. If disturbance is unavoidable, the applicant must submit a mitigation plan prepared by a qualified individual, and the ultimate preservation-versus-destruction decision is made only after consultation among the Board of Supervisors, the Zoning Administrator, the Historic Preservation Commission, and the applicant.

A separate exemption applies to residential chain subdivisions of three or fewer total lots, which are exempt from the Historic Properties requirements of this section.