The Restorers’ Art of the Invisible
Fred R. Conrad/The New York Times
Visitors wandering through the Richard Pousette-Dart exhibition at the Solomon R. Guggenheim Museum seem oblivious to the scaffolding and hard hats in their midst. But for the people behind the scenes, the work unfolding within the museum’s curved white walls is as engrossing as the art displayed on them.
For the last three years a team of engineers, conservators and architects has been studying the guts of the Guggenheim, mapping out a thorough but respectful renovation of Frank Lloyd Wright’s spiraling building on Fifth Avenue, completed in 1959. Although it was clearly in serious need of renewal, with cracks in its facade, a decaying sidewalk and outdated mechanical systems, experts wanted to make a comprehensive diagnosis before determining the best course of treatment.
Now they have a plan — already in action — and the end is in sight. The work is expected to be completed by summer 2008. “It’s taken us three years to get to the point where we’re actually intervening,” said Pamela Jerome of Wasa Studio, the preservation architect on the project.
And on a recent walk through the museum, which will remain open throughout the renovation, the specialists involved talked about what they had discovered and strategies they have devised. Ms. Jerome has faced major renovation challenges before, including the sagging cantilevers and damaged stucco of Fallingwater, the residence designed by Wright in rural Mill Run, Pa.
But the Guggenheim’s structural complexities, she said, made this project more daunting. In addition to repairing the facade, the $29 million renovation involves upgrading the cooling systems and updating the elevators and bathrooms.
Perhaps the team’s most crucial realization was that workers in the 1950s had failed to provide continuous horizontal steel reinforcement in the walls on the sixth ramp, as they had on the lower ramp walls. The sixth is twice the height of the lower ones and leans outward at a different angle, the museum says.
The original building lacked insulation. In a 1992 project devised by the architect Charles Gwathmey, insulation was finally installed, improving the situation. But some gaps were left on the apron slab, where the floor meets the wall, creating condensation problems that are now being addressed. Strips of carbon fiber are being installed in the concrete walls to create a seamless, protective exterior envelope.
As the work proceeds, the walls’ interiors are exposed, as they must have been when the building was under construction. “It’s the first time we’re seeing what Frank Lloyd Wright saw,” said Glenn Boornazian, president of Integrated Conservation Resources, who is the principal conservator on the project.
Wright is never far from anyone’s mind. Paramount goals are to make the work almost imperceptible and to adhere to the building’s original form to the greatest extent possible.
“From a preservation point of view, you don’t want to change the external appearance,” said Robert Silman, president of Robert Silman Associates, the project’s structural engineers.
When it came to the windows and skylights, then, the specialists wanted to improve them without replacing them. The windows, though, are not double-glazed and don’t provide adequate insulation. So the architects decided to replicate their form but substitute new glass with advanced thermal qualities that has been tested for water and air infiltration. (They have not yet undergone tests for pigeon-proofing, Ms. Jerome said).
Similarly the conservators tried to find repair materials — concrete patching compounds, acrylic crack fillers, expandable surface coatings — that “would be physically and aesthetically compatible,” Mr. Boornazian said. After identifying about 20 manufacturers that deal with concrete restoration, they narrowed the list to six and then subjected their materials to rigorous weather testing.
“Just as Frank Lloyd Wright was on the cutting edge of using materials, he forced us to think of solutions in unusual ways,” Mr. Boornazian said.
Wright was among the first to use gunite — sprayed concrete — on a large architectural scale, which allowed him to create his smooth unbroken curves, Mr. Boornazian said. To give the Guggenheim’s surface a monolithic appearance, he added, Wright left out expansion joints, which would have created visual vertical breaks.
Wright’s professional reputation has emerged intact, experts involved in the project say. The building’s flaws lay in its execution, not its conception. Exposed to high winds and extreme variations in temperature, the walls have continually expanded and contracted. They will still be flexible but will become more resilient, with concealed control joints that allow the gunite to expand and contract without cracking.
As part of its preparatory research the team studied the Guggenheim’s archives, including photographs taken during construction; written documentation of the building process; correspondence between Wright and the contractor; and original architectural and shop drawings.
The building was then stripped of as many as 11 layers of paint, and experts conducted a 17-month survey of thousands of cracks of varying magnitude in the facade. Using impact-echo technology, in which sound waves are sent into the concrete and the rebound is measured, the engineers located voids within the walls.
To map the geometry of the museum and determine its load-bearing capacity, the engineers relied on laser measuring, a fairly tricky matter given the building’s spiral and its sloping walls. “We think it’s the largest laser model ever constructed,” Mr. Silman said. “It took up the whole memory on the computer.”
They also submitted their findings to two peer review panels of experts in architectural restoration, materials conservation, structural engineering as well as an environmental envelope specialist.
“We all believe, when we finish, this building will be better than new,” said Marc H. Steglitz, the museum’s chief operating officer. “And we’ll get another 50 years out of it.”