Minnesota State Capitol Repairs, Restoration and Preservation
Minneapolis      
Best Project

Owner: Minnesota Dept. of Administration
Lead Designer: HGA
General Contractor: JE Dunn Construction
Architectural/Historical Consultant: S.C.A. Schooley Caldwell Associates
Stone Consultant: WJE

The Minnesota State Capitol is on the National Register of Historic Places, but at 109 years old, the Cass Gilbert-designed landmark was in serious need of modernization.

The HGA-JE Dunn-WJE team adopted a phased approach to the $310-million project.

Using swing stages and industrial rope access equipment where necessary, WJE architects and engineers carried out a visual survey of the marble exterior before doing any design work. They recorded their observations on inspection data sheets using CAD elevation drawings drawn from laser scans of the 1905 exterior. At select locations, the team performed petrographic evaluations using field microscopy to determine the extent of stone deterioration. Designers also identified locations to extract core samples of marble, mortar and patch materials for laboratory testing.

The 302,000-sq-ft structure needed major improvements to its crumbling exterior as well as upgrades to the elevators, new MEP systems and mitigation of water damage, which was discovered after JE Dunn workers removed sections of marble staircases to reveal years of neglect and structural problems.

The team improved energy efficiency by installing 15 custom air handlers with fan-wall technology. Non-historical spaces in the basement were converted to mechanical rooms, but there was extremely low headroom—mostly 8 ft to structure—surrounded by 4-ft-thick, load-bearing structural walls. The fan-wall units had footprints much smaller than conventional air-handling units, which resulted in less energy usage and lower sound levels.

By the end, crews had made more than 20,000 repairs to the exterior stone work. That included 6,000 pieces of Georgia marble harvested from the same quarry as the original 1905 stone. More than 40,000 sq ft of public meeting space was added as part of the renovation. In addition, JE Dunn brought in art-restoration experts to meticulously update and repair the large murals and historic art on the walls. The project was delivered on time for the first legislative session in January 2017.

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