Facade of San Francisco Landmakr

This article appeared in FRSpectrum, Volume 3, No. 4, November 1995

FAÇADE OF HISTORIC SAN FRANCISCO LANDMARK IS RETROFITTED WITH FRP

The Owners of the historic James E. Flood building in San Francisco turned a restoration challenge into a restoration opportunity with Vetrotex CertainTeed's Chopped Strand Mat M127 and Woven Roving 324 glass reinforcements.

The situation involved removing sheet metal cladding that was installed by one of the building's tenants in a 1950's modernization effort, and restoring the structure's original, hand-carved sandstone arches, cornices, parapets and balusters. These ornaments were eliminated by the tenant who, 40 years ago, opened up a store on the bottom three floors of the building. In the 1950s, contractors hired by the store owner removed the building's original hand-carved ornamentation with jackhammers to properly install the sheet metal.

In 1993, the tenant moved out, leaving behind the sheet metal cladding on the exterior of the historic structure's first three floors. The owners of the Flood building decided to restore the look of the building's original sandstone façade. They hired an architect and retained a general contractor to determine the best approach to the project.

After careful study, William Kreysler & Associates of Penngrove, Ca., the fabricator chosen to work on the project, recommended that polymer concrete and fiberglass-reinforced plastic (FRP) be used to retrofit the building. He recommended polymer concrete for the balusters and suggested that FRP be used to fabricate the remaining pieces for several reasons: part of the project required the construction of large panels – FRP provided a strong, lightweight solution; the panels had to be thin because, when installed, they butt up against the building's steel structure – FRP could meet the thinness requirement without compromising strength; and some of the ornamental work, like cornices, was intricately designed – FRP is easy to engineer and provides substantial design flexibility.

Step-by-Step Craftsmanship
Most of the molds for the cornices and arches were made by working from the building's original 1903 architectural drawings; some were made directly from existing ornaments. Materials used to make the molds include urethane rubber, FRP and wood materials, depending on the shape required.

Vetrotex CertainTeed's Chopped Strand Mat M127 and Woven Roving 324 fiber glass reinforcements were combined with a Class I fire-retardant polyester resin, made by McWhorter (formerly Cargill), and hand-laminated into open molds to make the cornices and arches. This proprietary combination of materials gives the outer surface of the cornices and arches the appearance of the original sandstone surface.

While the cornices were made entirely from FRP, the arches required additional assembly. Once the fiber glass shell laminates were fabricated, the arch panels were anchored to a tubular steel frame, manufactured by Kreysler. The frame acted as an intermediary between the fiber glass arch panel and the structural steel of the building. It also helped to keep the panels stiff and simplified their installation.

Once the assemblies were made, they were shipped to the job site, lifted off of a truck by crane, aligned and fastened to the structural steel building by the installation contractor.

Overcoming the Challenges
The restoration was not without its share of challenges; cost was among them. Says President Bill Kreysler, "There were so many variables in this project, it was very difficult to predict the cost."

The use of FRP also presented a challenge. "FRP has physical properties that are different from the original sandstone material," says Kreysler. "FRP involves a different set of coefficients of thermal expansion and contraction. This had to be taken into consideration in designing the connections, waterproofing, interface between the exterior of the panels and doorways, and window frame."

A Realistic Solution to Today's Façade Retrofit Problems
The FRP approach proved to be a light-weight, realistic solution to this challenging renovation, which was accomplished in just 10 months. This unique use of FRP in this project earned William Kreysler & Associates the California Preservation Foundation Annual Design Award of 1994, as well as the Composites Fabricators Association 1994 Ace Award for Composites Excellence.

FRSpectrum is published quarterly by Vetrotex CertainTeed.

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Last updated: 09/21/06