Restoration of Terra Cotta Mansard Roof — Traditional Building

8/01/2003

Guarded on four corners by eagles with 4-ft. wings, the decorative terra-cotta mansard roof on Two Mellon Center, formerly the Union Trust Building, is undergoing a multi-million dollar, five-year restoration to eliminate the water problems that have plagued it since it was built. Designed by Frederick Osterling, one of Pittsburgh’s premier architects, and built by Henry Clay Frick, the building was completed in 1918.

The Flemish-Gothic style limestone structure occupies a city block in downtown Pittsburgh between Grant, William Penn Way and Oliver Streets and Fifth Avenues and reaches a height of 240 ft. It is known for its central rotunda capped with a stained-glass dome, the shopping arcade that was originally on the first four floors, the elaborate terra-cotta mansard roof and the two cathedral-style towers on the roof that house the mechanical components. Over the years, the freeze/thaw cycle had caused many of the tiles and architectural pieces on this mansard roof to become brittle and fragmented. Rain and snow seeped under the tiles, causing water damage to the building’s exterior and interior. It was the same story for the towers on the roof.

Built in 1915-1917, Two Mellon Center (formerly the Union Trust Building) occupies a city block in downtown Pittsburgh. The work on the terra-cotta mansard roof proceeded one façade at a time so the building can be kept open and occupied. Safety nets protect pedestrians below.

The building is currently owned by Mellon Financial Corp. and is used as commercial offices, but because of the leaks and the water damage, the 10th floor could not be occupied. Mellon called on masonry contractor Graciano Corp. of Pittsburgh to restore and repair the mansard roof and the two towers, under the direction of the Chicago-based architectural and engineering firm of Raths, Raths and Johnson. The project included repairs to the upper terra-cotta mansard roof, structural repairs to the roof, waterproofing to prevent further water damage, and replacement of terra-cotta tiles and sculptures as needed.

“The 12-story building, with two steeples that take it to 16 levels, is an exact replica of an 18th-century Belgian library,” says Bernard Koblinsky, Assistant V.P., Mellon Financial Corp. “The building leaked from the day it was built. It would have completely deteriorated if it had not been covered with tar during the 1930s and 1940s. You couldn’t see the tar because the building was covered with soot from the nearby steel mill.”

First and second shift supervisors Larry McIntyre (left) and Bill McCracken reassembled one of the repaired corner eagles after a portion was rebuilt. The next step is the final sealant.

The 65-ft. high mansard roof is 245-ft. long and is pitched at a 17-degree angle. Koblinsky points out that there are 38 dormers per side, along with lots of gingerbread and ornamentation, plus the two towers which are 54x50 ft. and 75 ft. tall. A 6-ft. balustrade extends around the perimeter of the roof and there are also two interior balustrades on the flat portion of the roof. The dormers are arranged in three tiers, with a row of small ones near the top, middle-sized dormers in the middle, and the larger ones on the bottom. “Most of the water came in through these larger dormers,” Koblinsky says, “so we were not able to occupy the 10th floor because of water damage.”

“They have tried to repair this roof since the day it was built,” he adds. “They tried again in the mid-1980s and in the early 1990s. Now it is finally being preserved and will be saved. The architects developed a waterdiversion system and Graciano is executing the repairs and restoration. These repairs have been successful; we found the right team. This is a premier building of this vintage in Pittsburgh. It is truly one of a kind.”

Repairs were required at the intersection of the mansard roof with a top dormer.

Launched in mid 1999, the mansard roof portion of the project is scheduled for completion at the end of this year, with the towers to be completed by end of the year, 2004. Graciano tackled one façade at a time. “ The biggest challenge is accessing the work while protecting the interior of the building and the public below as the repairs are completed,” says project manager Dave Sinclair. “Many areas are difficult to access because of the steep slope of the roof and the way the dormers project. Specialized rigging systems with individual man baskets were put in place. Because of the limited access, the work is taking longer than it normally would.” Sinclair adds that the firm is working two shifts, daylight and evening, and “we try to perform the more disruptive work in the evening.”

A special rigging system was developed for this project, with a series of outrigger and trolley beams. The outrigger beams of the scaffold project 17 ft. from the roofline to the vertical drop. “We built one of these scaffolding systems and then moved it around the building as the work proceeded,” Koblinsky explains. “ Each façade took about one year, except for the Grant Street façade which had severe deterioration. That took two years. We are approximately half done with the Oliver St. façade and expect to be finished by the end of the year.”

Although it looks beautiful, the ornate Gothic mansard roof on Two Mellon Center had been suffering from water damage for some time. The water damage extended into the interior offices on the 10th floor, which had become unusable.

Replacement elements are being fabricated by Architectural Restoration Castings of Ambridge, PA, using GFRC instead of terra-cotta. “It’s a more contemporary material, about 30 years old,” says Sinclair, “and is being manufactured to match the existing terra-cotta. It is less expensive and it’s faster to have pieces made and delivered to the site,” he adds. “ We don’t know which pieces have to be replaced until the engineer evaluates the condition of each one. Then we have them removed and sent to the fabricator.”

“The GFRC is more durable, 15% less expensive, and can be procured in about half the time,” says George Mulholland, engineer with Raths, Raths and Johnson.

All four of the terra-cotta eagles (each one projects 6 ft. from the building and has a wingspan of 8 ft.) on the corners of the building required some replacement parts, Sinclair notes. “We replaced different elements on each one, sometimes it was the wings, sometimes the feet, but we replaced at least one wing on each eagle.” The 3-ft. finials on top of the balustrades are also being replaced with GFRC molded to match the originals.

Scaffolding is being erected on one of the two towers on the roof. These house the mechanical components of the building. Extensive terra-cotta repair and replacement is planned for these structures.

In addition to replacement items, the project includes many repair items, including the installation of a water diverter system at each dormer, anchoring, pinning, caulking, stitching, pointing and coating, Sinclair notes. “ There is also some steel replacement due to years of water infiltration. For example, some of the steel angles and channels that the terra-cotta is anchored to had to be replaced, and we had to supplement or replace sections of steel at many of the dormers.” Another structural repair involved fabricating and installing different types of pins to anchor the terra-cotta and hold pieces together.

While Graciano workers, all Local 9 Bricklayers and Allied Craftworkers Union members, are working on the Oliver St. façade, scaffolding is being erected for the towers on the roof.

Founded in 1916, Graciano is one of the oldest family-owned masonry restoration firms in the country. Other projects have included the Queensboro Bridge, Rockefeller Center and Shea Stadium in New York City.

Koblinsky points out that the flat portion of the roof was also replaced. “We also had the metal marquees at the street level restored.” This work was done by Hall Industries of Pittsburgh.