Engineer who saved Fallingwater

Robert Silman, a structural engineer who rescued Frank Lloyd Wright’s cantilevered Fallingwater in Pennsylvania from the edge of collapse — and preserved dozens of other landmarks, too — died July 31 at his home in Great Barrington, Mass. He was 83.

He had multiple myeloma, a form of cancer, said his wife, Roberta Silman.

Mr. Silman was president emeritus of the engineering firm Silman, headquartered in Manhattan, which he founded in 1966.

Though he came of age when engineers were expected to perform feats of awe-inducing bravura, Mr. Silman largely contented himself with the invisible, ingenious stitchery that protected the work of other engineers and architects.

“Any time we faced any intractable problem in trying to save a building, we called Bob,” Peg Breen, president of the New York Landmarks Conservancy, said Friday.

Among the best-known projects he helped engineer were the creation of the Ellis Island Museum of Immigration, the restoration and expansion of Carnegie Hall, and the preservation of the Survivors’ Stairs from the World Trade Center.

But it was in rural Pennsylvania, southeast of Pittsburgh, that Mr. Silman earned a national reputation. There, Wright designed Fallingwater, one of the most breathtaking houses of the 20th century, for the Pittsburgh merchant Edgar Kaufmann and his wife, Liliane.

Fallingwater seems to erupt from the forest around it, with terraced slabs jutting up to 14½ feet — seemingly without support — over a waterfall in the Bear Run creek. The daring cantilevered design conferred celebrity status on Wright after its completion in 1937.

Even before that, Kaufmann wondered whether Wright had specified enough steel reinforcing bars in the concrete beams of the main cantilever. Wright resented the questioning, but Kaufmann saw to it that extra reinforcing bars were installed anyway.

Ultimately, that precaution was not enough. “In the mid-1990s we heard from an engineering student that his research showed Fallingwater might be in structural trouble,” Lynda S . Waggoner, director emerita of Fallingwater, said Monday.

“According to his calculations, the cantilevers were under-engineered and in danger of failure,” she continued. Ms. Waggoner telephoned Mr. Silman. “After what seemed like minutes but was likely seconds, he responded, ‘I will have someone down there this week.’”

By then, one cantilevered slab was tilting about 7 inches downward from its original position, a condition known as deflection. Mr. Silman persuaded Fallingwater’s owner, the Western Pennsylvania Conservancy, to erect temporary steel shoring under the slab. In 2001, flagstone flooring and built-in furniture was removed from the slab to expose the concrete beams and perpendicular joists below.

Five cables — made of as many as 13 half-inch-diameter steel strands — were placed alongside three major beams, like tendons and bone, with six smaller cables placed alongside the joists. This steel network was anchored to the existing concrete piers under the house, then tautened to restore structural integrity to the cracked beams. The operation has been likened to orthodontics.

“Bob’s solution to the faltering cantilevers was elegant,” Ms. Waggoner said. “It preserved the material integrity of the building and minimized any incidental damage while preventing future deflections.”

The six-month project “ensured Fallingwater’s ability to continue to amaze visitors from the world over for generations to come,” she said.

Doing the impossible was something of a specialty for Mr. Silman. Preservationists who wanted to save the staircase at the World Trade Center, down which hundreds of survivors fled to safety on Sept. 11, 2001, faced a seemingly insurmountable hurdle. The staircase — 22 feet high, weighing 175 tons — had to be lowered from street level into the underground National September 11 Memorial Museum.

“No government agency wanted to try,” Ms. Breen said. “Bob figured out how to safely remove the stairs and treads, designed a ‘cradle’ to hold them and then worked with the Port Authority on safely lifting them into place. Never would have happened without Bob.”

Guy Nordenson, who heads a structural engineering firm bearing his name, said by email: “Bob Silman will be remembered as one of the great New York engineers, one that kept the ‘civic’ alive in civil engineering. He led the restoration of the structure and fabric of the Guggenheim Museum, and worked closely with Renzo Piano to reinvent the Morgan Library campus, renewing these and other key New York institutions.”

Robert Silman was born May 19, 1935, in Rockville Centre, N.Y.

He graduated from Cornell University with a bachelor of arts degree in 1956. At New York University, he received a bachelor’s degree in civil engineering in 1960 and a master’s degree in 1963.

His firm, Silman, has 160 employees in New York, Washington and Boston. Preservation accounts for about one-fifth of the firm’s work.