Sometimes, the best way to restore an historic building is not the way it was originally built. The methods and materials of construction have changed, and newer options are available to re-create the original design. Labor-intensive approaches of a century ago are now prohibitively expensive. This 
is especially true in the case of decorative details, which were sometimes hand-made. The range of available materials, by contrast, has expanded, offering the restoration architect more choices for achieving original appearance and function, and making it more durable and high-performing in the process.

Fiber-reinforced polymer composites (FRP) using glass fiber—commonly referred to as fiberglass—are increasingly being used to create large-scale architectural elements for restorations.1 FRP is extremely durable, does not corrode or rot, and bears the elements well. A single mold can be used multiple times in repetitive designs for economies of scale. One-off elements can often be created cost-effectively compared to alternative materials.

FRP holds detail sharply, and it can be colored and textured for a wide range of finishes. It is also lightweight—a massive, solid block of masonry can be replaced by an FRP shell a mere 6 mm (¼ in.) thick, reducing dead load and considerably simplifying installation. As FRP gains acceptance in construction, restoration is emerging as an area where it can be an effective solution for bringing faded grandeur back to flower.

Desecration of Detroit
Architectural restoration may be considered the act of re-fulfilling the original design intent. In many cases, 
it is an implicit acknowledgment the architect’s ideas have outlasted the original materials, so it makes sense to preserve those ideas with new materials that are more durable, more appropriate, or both.

This is exactly the case with a series of restorations that have been happening in downtown Detroit, Michigan, where decorative masonry—long ago stripped from buildings—is being recreated in FRP. The old downtown is the site of many majestic late 19th and early 20th century buildings that once featured ornamental masonry, including large cornices crowning the classically inspired designs.

Then, in 1958, natural deterioration had its way with one such structure. 
A 6-m (20-ft) piece of cornice fell off the Ferguson Building, killing 80-year-old pedestrian Myrtle Taggart below. The mayor called for the elimination of “dangerous gingerbread,” and the city issued more than 1600 cornice violations. Rather than bring their cornices up to code, many owners simply stripped off the architectural crowns, leaving the edifices looking bare, their scars patched with (often mismatched) brick. Some went further, and ‘modernized’ the building exteriors, stripping almost all ornament. And thus it stayed for decades.

Whitney – Historic copy
The restoration architect had access to this photocopy of historic detail drawings of the David Whitney Building’s exterior. This portion shows the sign on the top of the building, as well as a large wreath above it. This document details considerable ornamentation. A series of photos from 1940 revealed some of the ornament was no longer present; that 1940 version of the building served as the basis for restoration. Images courtesy Kraemer Design Group

Now, following Detroit’s bankruptcy and the cratering of real estate values, many of these buildings have turned over ownership. The new owners are repurposing old commercial space into residential and mixed-use buildings, aided by tax credits for restoration of historical buildings. The grandeur of downtown Detroit is returning. In numerous instances, the masonry has been recreated with glass-fiber composite elements that look like the originals, but are a fraction of the weight of stone or terra cotta.

Rebirth of a grand edifice
The 19-story David Whitney Building is an illustrative case. Built in 1915, it occupies a prime location along Grand Circus Park at Woodward Avenue, in the heart of the city. With an august exterior, and a spectacular four-story sky-lit atrium at the center of its grand lobby, it quickly became a fashionable commercial address, tenanted by numerous medical practices. The building became well-known to generations of Detroiters who passed through its doors on the way to see the doctor.

It was ‘modernized’ in 1959, stripped of ornamental masonry and transformed into ‘mid-century modern.’ By the late 1990s, however, the building was vacant, and remained so for more than 15 years. The current owners began renovating the structure into a combination of hotel, high-end apartments, and retail in 2012. The remodel included restoration of the grand lobby, and re-creation of exterior ornamentation.

“The challenge,” explains David Di Rita, a principal of the Roxbury Group, the building’s owner, “was to bring back a 100-year old building that had never really served a modern purpose. It was never air-conditioned, the windows were never replaced. It’s all original mahogany and marble. The question was how to preserve what was remarkable about this building and yet drag it into the 21st century.”

The restoration architect, Kraemer Design Group, had access to historic architectural drawings but only via fuzzy photocopies. They also had good photography of the building from 1940. A comparison of the two sources revealed that some of the most florid aspects of the originally designed exterior ornamentation were already gone by 1940. They used the 1940 version of the building as the basis for the current restoration.

Sarah Rabe, an architect with Kraemer Design Group who was closely involved with the project, says, “We were very lucky. We were able to pull enough info off those that we’re reasonably sure they are close to what was on the building originally.”

The restored elements constitute some of the main façade features of the original design. The glazed brick façade was divided by terra cotta water-tables at the fifth, 15th, and 16th floors. A terra cotta cornice adorned with bas relief lion’s heads crowned the 19th floor. There was a large sign atop the building proclaiming its name.

Restoration elements were at first detailed by the architect in sheet metal. As the project progressed, this selection was re-examined. The contractor responsible for constructing with the architect was Ram Construction—a specialty contractor in high-rise façades with extensive restoration experience. That firm had previously worked with FRP elements on restoration projects, and thought it might be a better solution than sheet metal. The head of the company, Bob Mazur, was concerned the sheet metal would begin to rust within a few years. He was also afraid of ice damage, denting, and oil-canning (i.e. a wavy deformation of a sheet metal surface supposed to be flat or smoothly curved)—any of which could mar the effect. For him, it was a matter of not only business, but also local pride.

Using FRP would allow the restoration of the lion’s heads on the cornice, which was a detail left out of the sheet-metal design as unfeasible. The lion’s heads proved to be an important factor for the owners.

Consulted about the feasibility of substitution, an FRP fabricator made a 4-m (13-ft) long mockup based on the architect’s drawings, using a mold made of micaboard to cast the FRP. A cream color, slightly warmer than the building’s white glazed brick, was selected. When the mockup was placed against the building wall, the owners declared the color “perfect.” Used on all the FRP elements of the project, it was given 
a fine matte finish, similar to the texture of drywall spackle.

The FRP parts cost more than sheet metal, but, according to project manager Jim Nystrand, installation cost was reduced. Sheet metal as designed required extensive wooden framing behind it to give it strength. The framing had to be constructed 60 m (200 ft) up in the air, and then have the sheet metal attached to it. The FRP water-tables and cornices were cast in the shop; they were so lightweight and strong they required only very simple framing attached to the building. A team of three or four could install eight panels a day.

Recreating the past
The FRP elements were fabricated using techniques employed for decades in the fiberglass industry. A pattern—essentially a full-size mockup of the final piece—is constructed in wood, with the addition of clay or other materials necessary to achieve all the desired shapes in the element. The pattern is painted for a smooth finish, and then waxed. On that pattern, a fiberglass mold is cast. The mold is a negative image of the final shape. That mold is then used to cast multiple fiberglass elements actually installed on the building.

The water-table and cornice pieces are designed with overlaps, alternating sections being either ‘overs’ or ‘unders,’ so there are two different molds for all the pieces of the cornice. The sections were either 1.8 or 2.1 m (6 or 7 ft) long—the ‘under’ sections have a lip extending behind the ‘over’ section. Large, flat areas are sandwich panels comprising two layers of 5-mm (3/16-in.) FRP surrounding a 13-mm (1/2-in.) balsa core to prevent oil-canning. Each section has a full return at the end
to act as a fire stop.

Corner pieces are made simply by miter-cutting and joining straight sections. The part of a panel that gets fastened to the building is slightly thickened to 6-mm (¼-in.) FRP. Certain high-stress areas have a double thickness of FRP, but they account for only about five percent of the total surface area.

To cast a fiberglass panel, the mold is first coated with gelcoat, which both seals the surface of the fiberglass and has the finish color integrated into it. Modern gelcoats have ultraviolet light (UV)-inhibitors to protect the resins from the sun. (The material does not rot, corrode, or support mold growth.) Then, a mixture of resin and chopped glass fiber is sprayed into the mold and hand-rolled for compaction and adhesion. It cures through air exposure in two to three hours.

For the David Whitney Building, the 26 lion’s heads on the cornices were made by a slightly different method. The pattern was sculpted in clay by sculptor Sergio DeGusti. A silicone mold, taken from the clay, was used to make each of the bas reliefs, which were then cast into the panels that bear them on the building.

Each head is about 900 mm (36 in.) in diameter, with a 50-mm (2-in.) border framing it, for a total 1000-mm (40-in.) diameter casting. Each is approximately 50 mm (2 in.) thick, and weighs about 45 kg (100 lb). The terra cotta originals are estimated to have weighed 180 to 227 kg (400 to 500 lb) each.

To attach the water-tables and cornices, two strips of 2×6 lumber were anchored to the building. The edges of the FRP element fit over the top strip and under the bottom strip, and are fastened to the wood with screws. Most pieces—other than the sign atop the building—were light enough to be hoisted up the building on the swing stage, without the use of a crane, and then positioned and anchored by three or four men—two on the swing stage and others at nearby windows or on the roof.

Di Rita also notes that after the mockup was placed on the building, it remained in place for about a year before the permanent FRP water-tables were installed. At that time, he found it indistinguishable from the new pieces in color and texture.

The sign atop the building was made in three large panels, and was hoisted into place by crane. Each FRP panel has three horizontal strips of paired 2x6s attached inside, running the length of the panel. Anchored in the 2x6s are 16-mm (5/8-in.) stainless steel threaded rods, either 15 or 18 per panel, depending on its size. The rods stick straight out the back of the sign.

The fabricator provided the contractor with templates of the exact positions of the rods, allowing the contractor to drill anchor holes in the masonry wall of the penthouse atop the building. Each piece of the sign was held aloft by the crane and the rods aligned into the holes in the wall—a tricky procedure, but one performed successfully due to both the templates’ accuracy and the contractor’s skill.

David Di Rita’s recollection of the installation of the sign underscores the emotional aspect of architectural restoration. For him, it was a transformational event.

“That sign went up like three pieces of Lego, all in about three or four hours. It was the most amazing thing I’ve ever seen,” he said. “Three large pieces go up and just slide into place, and instantaneously restore this huge sign. It was such a dramatic change to the look of the building in a single day.”

Architect Rabe believes that, with both the cornices and the sign, the fiber-reinforced polymer composite restorations fulfill the design intent.

“We feel that what is up there now best represents the old version,” she said.

A rising tide
This is one of several restoration projects in Detroit that have benefitted from FRP elements. The Book Cadillac building, completed in 1924 and designed by Louis Kamper, was renovated in 2008 as a mixed hotel and condo development. It had an FRP water-table installed at the 23rd floor, made from drawings provided by Sandvick, the restoration architect.

In the case of the Gabriel Richard Building, also from the 1920s, the original decorative elements were still partly in place, but parts were badly deteriorated. About 30 percent of the building’s scalloped cornice, and 122 lineal m (400 lineal ft) of decorative band and were replaced to match the existing terra cotta. Silicone molds were made from the existing original elements and used to cast FRP to match.

There are several more FRP restoration projects planned in the near future.

Conclusion
Although fiber-reinforced polymer composites have been used in architectural applications for more than 50 years, it is still a ‘new’ material to many design professionals, unfamiliar and a bit mysterious. FRP is seeing a greater acceptance construction now, both in the re-creation of historical detail and for the fabrication of modern shapes that have previously existed only in a computer model. The increase is due in part to the development of new and better resins and gelcoats. Fabrication methods perfected in the boat-building and aerospace industries have also contributed to the versatility of the material.

With the use of both traditional fabrication techniques, as well as digital methods of scanning and restoring deteriorated details, a wide variety of façade features and interior details can be realized in FRP. As more of these projects are built, FRP will inevitably become a more familiar and top-of-mind material when designing both restorations and new construction.

Guy Kenny is president of Glassline Inc., a composites fabricator with more than 50 years of experience in making glass-fiber-reinforced composites for architectural applications, including numerous historical restorations. He can be reached at glassline1@earthlink.net.

Steven H. Miller, CDT, is a writer and photographer specializing in issues of the construction industry, and a freelance marketing communications consultant to building product manufacturers. He can be reached at steve@metaphorce.com.

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