MARSHALLTOWN, IA — On July 19, 2018 an EF-3 with a recorded 144 mph wind tornado hit the center of Marshalltown, Iowa, leaving a path of destruction. The Marshall County Courthouse was one of the buildings damaged by this storm.

The force of the tornado twisted the dome and bent the spire from its place at the courthouse pinnacle. Following the storm, OPN Architects was hired to provide a conditions report. The initial evaluation included a review of code issues, building loss, structural damage, subsequent water damage to the building interior and site elements damaged or destroyed.

A 3D building scan revealed a detailed and nuanced view of the damage, including twisting and deformations not perceivable through visual inspection. The existing wood dome structure and sheathing had been twisted and damaged beyond repair. The original wooden structure and skin of the dome was determined to be damaged beyond salvage. This provided an opportunity to replace the existing historic dome with one that would last for another 150 years.

Dedicated on November 19, 1886, the five-story, limestone and brick courthouse was designed in the Neoclassical style by John C. Cochrane of Chicago, Illinois. The building is rectangular in plan and sited on an east-to-west axis. The rectangular form is organized around a central rotunda that extends from the second through fifth floors and crowned with a square-plan clock tower capped by a convex-mansard roof with chamfered corners. In 1977, a 35-foot-tall fiberglass and sheet metal spire and lantern was installed. The building has retained much of its original architectural and structural elements.

The new dome will be constructed of steel with new ladders to provide the county adequate access for inspection and maintenance. The steel structure will be clad with a two-part custom rain-screen with Bermuda-style lapped copper to match the angles and profiles of the damaged historic dome. The copper panels will be removable to allow for replacement as required.

The spire that was removed during the storm will be rebuilt to match it’s 1977 original, and topped with a new weathervane, using the original construction drawings from the 70s for reference. The architectural detail elements will once again be made of fiberglass to replace those from the 1970s. In addition to the work on the dome and spire, restoration will include the clock tower, gutters, roofs and replacement for seven of the eight limestone chimneys. There will also be new exterior building lighting, trees and interior renovations to repair water damage and address code issues.