3D scans see into eye of storm’s damage

Marshalltown Courthouse Post (3)Scans show dome beyond repair

On Thursday, 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 1886-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 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.

Marshalltown Courthouse Post (8)

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 a unique 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, 35-foot-tall fiberglass and sheet metal spire and a lantern were 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 70’s for reference. The architectural detail elements will once again be made of fiberglass to replace those from the 1970’s.  In addition to the work on the dome and spire, the restoration will include the clock tower, gutters, roofs, and replacement for seven of the eight limestone chimneys. New exterior building lighting, trees, and interior renovations to repair water damage and address code issues.

Marshalltown Courthouse Post (9)

Marshalltown Courthouse Post (7)