Natural Stone: Restoring the Minnesota State Capitol

natural stone restoration

2016 MIA+BSI Grande Pinnacle Award

By Maureen Upchurch

Photos courtesy of Polycor, Twin City Tile and Marble, and HGA Architects and Engineers

What do you get when you mix 30,000 pieces of existing exterior façade stone, a quarry that is no longer in use, and a team of 13 AEC and trade professionals from around the globe? You get the prestigious 2016 Grande Pinnacle Award from the MIA+BSI for the exterior restoration of the Minnesota State Capitol Building in St. Paul.

With such an expansive and extensive project — valued at nearly $60 million — where did the team even begin? In 2010, they started with a block-by-block analysis of the exterior of the building. For the first several months of the project, representatives of HGA Architects and Engineers, Wiss, Janney, Elstner Associates, Inc. (WJE), and JE Dunn Construction assessed each of the 30,000 pieces of stone on the exterior façade, tapping and sounding each of the decorative elements to forensically determine its integrity. Ultimately, it was determined that more than 60 percent of the building required some level of treatment.

2016 MIA+BSI Grande Pinnacle Award

“Phase One was a mini-project to test the process,” says Ginny Lackovic, associate vice president for HGA. “It allowed the design team, stone masons, carvers and suppliers a chance to determine their individual and combined strategies to complete the project. It was also essential to the state of Minnesota in determining final overall project budget.”

The exterior analysis defined a three-tiered system to determine which pieces needed to be replaced. Was the stone a threat to life safety (Tier 1)? Were water-shedding features no longer performing as originally designed (Tier 2)? Had the character of a piece deteriorated enough to mute its historical and aesthetic integrity (Tier 3)?

exterior restoration of the Minnesota State Capitol Building in St. Paul

It was essential to get the owner of the quarry, Polycor, Inc., involved early in the process. Seeking to use Georgia White Marble, found only in the firm’s Tate, Ga., location, the Minnesota State Capitol received permission from Polycor to re-open its facility for this specific use. More than 6,900 cubic feet of the marble was employed for the project — the same marble used in structures such as the Lincoln Memorial, St. Patrick’s Cathedral in New York City and the original Minnesota State Capitol Building. “We worked with the architect to select the material ahead of time,” says Sylvie Beaudoin, project manager at Polycor. “They bought it early to ensure that there was enough supply and that the color was correct to match the existing building.”

Each stone and its desired outcome was laid out — full replacement, partial replacement, crack fill, etc. Twin City Tile and Marble began measuring these and created corresponding shop tickets. “We talked to Polycor about lead time,” says Joe Becker, vice president of Twin City. “And we worked with them to find fabricators of stone with different specialties.” By the end of the project, five fabricators were employed from the United States, Canada and Italy. When the shop tickets were completed by phase, they were sent to Beaudoin at Polycor, who would sort the tickets and have the stone cut per the requested dimensions and profiles. “Based on the tickets and my knowledge of the scheduling, I determined the right fabricator for each ticket,” Beaudoin recalls. “I would inspect every piece of the stone, and I would send it to them.”

exterior restoration of the Minnesota State Capitol Building in St. Paul

It was imperative that the fabricators held strict tolerances. There could be no assumptions, though there were only drawings of what was measured. “Not every stone was rectangular,” says Becker. This meant the measuring had to be on point and fabrication had to conform precisely to dimensioned shop tickets. This was critical to keep the installation process on schedule, as Mark 1 Restoration had to cut the pocket for the stone prior to receiving the finished piece. Across every phase, pieces were reviewed by the architectural and engineering team eight to 12 times, and the result was practically perfect. Attention to detail paid off, as there was a less than 1% error rate on the nearly 4,000 fabricated pieces.

 New pieces of Georgia White Marble were blended into the old to replace only the deteriorated areas.

New pieces of Georgia White Marble were blended into the old to replace only the deteriorated areas.

“When we took the first pilaster off the building, it was heart stopping,” remembers Lackovic. “We were hopeful that historically accurate replacements could be fabricated, but at that point we didn’t have approved models. We spent a lot of time with the fabricators to ensure that new work would be true to the original design. When the pieces came in, they were so beautifully crafted; everyone was able to relax a bit.”

Several of the building’s signature features had deteriorated, to the point that restoration was no longer a viable option. To re-create these elements, master carvers hand-tooled blocks of stone on-site, exactly as had been done a century ago. Blank stone was purchased and either installed first or carved on the ground (allowing easier access) to 50–60 percent completion before being put in place. Becker comments, “From there it was installed and blended to make it look like it was always there, having just a bit more white in color than the stone that had aged and grayed.”

 Skilled stone carvers were employed to help restore the beauty of the Capitol building.

Skilled stone carvers were employed to help restore the beauty of the Capitol building.

The building’s intricately carved pilaster and column capitals have more than 1,600 acanthus leaves. However, “a leaf is not a leaf,” says Becker. “If you measured each, they were not all the same size.” After measuring and analyzing the range of sizes, a prototype was developed. Paulo Costa and Sons in Italy worked on a model and were able to mass produce the leaves, a rarity on this project.

The leaves were not the only embellishments. The façade of the building was filled with unique, ornate carvings. There were several swags with fruit adorning the building. When these were in need of replacement, small blocks were put in place, and Margaret “Mimi” Moore of Moore Carving carved the fruit. Deterioration was so advanced, it was hard to tell the original detail — was it a melon or a pineapple? Historic images taken during the original construction were an invaluable reference from which. Moore could sculpt. This ensured architectural, as well as historic, integrity.

 Each new piece of stone had to be precisely fabricated and then blended to fit the pocket where the old stone had been.

Each new piece of stone had to be precisely fabricated and then blended to fit the pocket where the old stone had been.

 Each new piece of stone had to be precisely fabricated and then blended to fit the pocket where the old stone had been.Historic integrity and consistency were a large piece of the Minnesota State Capitol puzzle. Stone carvers are artists, and each has an individual eye for aesthetics. Rather than allow for varying points of view, HGA established design standards. Ribbons on newly fabricated scrolls could be off by half an inch and would have to be modified by Twin City Tile and Marble carvers. When new personnel would join the project, they were given this frame of reference. It was important when updating these pieces that variation from piece to piece was minimal.

Additionally, Advanced Masonry was tasked with patching. “Sarah Arkeh and Krista Rogers colorized the new stone to match the patina of the existing stone,” says Tim Miller, president of Advanced Masonry. “Their work was like a snowflake; no two pieces were the same.”

 The ribbons on newly fabricated scrolls could not be off by more than half an inch prior to being modified by carvers.

The ribbons on newly fabricated scrolls could not be off by more than half an inch prior to being modified by carvers.

“The pool of master stone carvers is somewhat limited,” observes Lackovic. “We were very fortunate to find so many talented people with such highly developed skill sets. Without them, we could not have accomplished what we set out to do.”

The patching, blending, installing and carving were phased horizontally around the building. “When they took the scaffolding down from the first phase, we were able to finally get a full perspective. It was the second time my heart almost stopped,” says Lackovic.

Although the team was deliberate and holistic in its approach, there was concern that a mix of new and old stone would detract from the dignified appearance of the building. It didn’t, thanks to the forethought of HGA and WJE to balance the location of the work, and due to the superior patching and blending of the stone by the masons on the team. A clean and smooth finished project was unveiled.

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