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Civil Engineering Magazine THE MAGAZINE OF THE AMERICAN SOCIETY OF CIVIL ENGINEERS

Sidebar 1 Preserving the Rotunda

By D.Y., S.B., and S.C.

Over the years, rainwater had leaked through joints in the dome and roof of the Minnesota State Capitol, damaging the stone, plaster, windows, and decorative paint in the building's vast and gorgeous rotunda. Repair and preservation were imperative.

An extensive scaffolding system weighing 250,000 lb was erected inside the rotunda. This process was closely coordinated with the installer's engineer to ensure the weight of the scaffolding and materials was well distributed and did not exceed the capacity of the rotunda floor, which covered an occupied committee room below.

In the rotunda and throughout the rest of the building, plaster, murals, and decorative paint were tested. All proved to be much more fragile than the team had originally anticipated. In some cases, whole murals peeled away from the walls before restoration could begin; in one of the committee rooms, the corner of an ornate ceiling mural-never properly affixed-had come loose.

Some plaster repairs had been done in 1915, and the team wanted to preserve the original materials and the 1915 repair materials wherever possible while minimizing the need for future maintenance. In conjunction with the Minnesota Historical Society, which owns the artwork and murals in the capitol, these historic treasures were painstakingly preserved.

Additionally, in the office areas, carpet was removed to reveal the original mosaic tile floors. The capitol originally had 30 skylights. Over decades of remodeling, drop ceilings comprising laylights had been installed beneath 10 of them, and mechanical, lighting, and sprinkler systems had been installed within these. So, in addition to restoring the historic leaded glass laylights, the team rerouted the mechanical and building systems around the restored skylight openings.

-DY, SB, and SC

Civil Engineering, December 2019, © American Society Of Civil Engineers. All Rights Reserved

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