Restoring historic structures with cast stone
Rehabs and restorations case study
By Jan Boyer
As the magnificent historic buildings across America are aging, restoration will be required to maintain and save these structurally sound buildings, rather than demolish and rebuild. No matter what the natural stone or concrete-based material originally used on the building, cast stone can be a solid choice for the restoration efforts, due to its unique capabilities and potential for outstanding craftsmenship. The following case studies demonstrate the versatility of cast stone in restorations.
714 Main Street – Farmers & Mechanic Building – Ft. Worth, TexasThis project involved restoration of a historic 200,000-square-foot office tower, originally built in 1920 and located at a popular crossroads in the downtown center. It involved replacing various veneer materials, both terracotta and GFRC, with cast stone on the first two stories. The building was ornamented originally with heads of Roman soldiers at the second floor level as palace guards. In previous renovations of the structure, the heads of the Roman soldiers were removed. The only remaining historical reference was old photographs. In order to reproduce the Roman soldier heads in cast stone, original artwork was produced, and then a series of molds were made. The molds required significant detail that included the facial expression, and the final product was reviewed by historians for accuracy.
The veneer pieces that formed the remaining parts of the exterior of the first two stories were challenging to produce as, in many cases, they had to form around the large heavyweight soldier heads. This visual challenge to achieve the look of the original terra cotta was met by adding black blasting material to the batch design.
The detail and the exacting design of the Roman soldier heads, in accordance with original pictures, was the primary goal of this project. Cast stone and casting techniques were critical in providing the detail necessary to restore this building to its original conception.
Princeton University Press – Princeton, New JerseyShowing that cast stone also is a viable choice for structural applications, this hardscape restoration project involved replication of a collegiate gothic courtyard entrance, originally erected in 1911. The extreme detailing and massiveness of the piece as well as replicating the original exposed aggregate in the cast stone elements made this an extremely interesting project.
The scope of the project included the complete replacement of the existing ornate cast stone structure, including the jambs, radius arch with rosettes, decorative panels, towers and coping. In order to accomplish the original intent, the cast stone arch was fabricated as a one-piece design and was structurally engineered to support the loads of the opening. This significantly reduced the installation cost and timeframe.
The molding process was extremely complex, as the one-piece cast stone arch incorporated numerous architectural details, including rosettes, surround profiles, decorative panels, and false joints all into the same mold. Therefore, the mold was fabricated out of a combination of materials that included wood, fiberglass and rubber, in order to be able to replicate the fine architectural details as well as to be able to “de-mold” the element after casting.
“Cast stone was also effective in terms of flexibility in design,” says Jeff Frake of Masonry Preservation Group. “[The project team was] able to make design changes and improvements that we would not have otherwise been able to do with natural stone.” (See the cover of this issue for another look at the finished project.)
Joseph P. Kinneary Federal Courthouse – Columbus, OhioBuilt in 1934, with funding from the President Franklin Roosevelt Public Works Administration economic recovery program, the entire façade of the building is sandstone, taken from a quarry in northern Ohio in 1932. The huge, seven-story building is undergoing a complete exterior renovation, with cast stone replacing the original sandstone. The Ohio Historical Society is involved with the project, along with the architect, to ensure that the cast stone is produced in such a manner that it will be an exact match to the existing sandstone, to maintain the integrity of the original design.
Phase 1 of the restoration has begun involving the replacement of the sandstone on the top three floors with cast stone as the material of choice, due to its versatility in color, texture and shapes for the stones. To ensure that the texture was correct, multiple pieces from the building were delivered to the cast stone manufacturer’s plant, and then castings were made from each of them. The samples made from the castings show the striations and blending of colors in the cast stone, creating just the right look. In addition to color and texture, each original stone, when removed from the building, is numbered, a mold is produced, and the stone is cast with exactly the same look and size as the original.
To add to the complexity of the project, the Federal Courthouse will continue to be in session, requiring all of the work to be performed from 6 p.m. to 4 a.m. only. This includes everything from demolition and shipments to installation. Given the location in Downtown Columbus, one elevation is bordering a river, two elevations have road frontage, and one elevation has a city park connected to the property. The location also affords little on-site storage, so communication among all team members is vital.
Originally published in Masonry magazine.
About the Author
Jan Boyer is Executive Director of the Cast Stone Institute. For more information, visit www.caststone.org or call 717-274-3744.