COOKFOX Architects' restored Andrew Geller's Pearlroth House (foreground) and designed a new house behind it, commissioned by Geller's client's son, Jonathan Pearlroth.

In what seems like unalloyed good news, Andrew Geller’s Pearlroth House, a box-kite-like icon of midcentury modernism, has been saved. The house in Westhampton Beach, Long Island, completed in 1959, was moved 40 feet inland by COOKFOX, the Manhattan architects, who are also restoring it. Jonathan Pearlroth, a lawyer and the son of Geller’s clients, has built a new house, also designed by COOKFOX, on the original site of what he calls the “double diamonds.” Pearlroth plans to open Geller’s 600-square-foot building to the public, by appointment, which he says will be easy to do now that it is closer to the road and now that his family has another place to live.

Pearlroth says he wasn’t always as appreciative of Geller’s structure as he is now. “It was just my house,” he says of the place where he spent summers as a child. “Meanwhile, I needed a bigger place for my family.” That created a dilemma. When Jake Gorst, Geller’s grandson and a documentarian, interviewed him about the house in 2005, Pearlroth spoke of possibly tearing it down.

Gorst, who has devoted much of his life to burnishing his grandfather’s legacy (Geller died in 2011), organized fundraisers to help save the house, which Pearlroth was willing to give to a nonprofit. But even harder than raising money, he says, was changing the public’s opinion of the house. “When we started this people were calling it refuse on the beach,” he says.

It didn’t help that the house had been enlarged in the 1970s, with a pair of motel-like rooms. The additions were “ugly,” Pearlroth says. And they were so badly built that they were endangering the original structure, says Gorst, who added that his grandfather was shocked when he saw the new wings. Eventually, Gorst found a nonprofit that was willing to turn the house into a beach pavilion on public property. But that deal collapsed, and the financial meltdown of 2008 made further planning difficult. Pearlroth, while waiting for resolution, let the house go downhill. But at least it remained standing.

In the meantime, Gorst met Manhattan architect Rick Cook—a self-described Geller obsessive—at a Geller exhibition. (Cook says he needed someone to talk to about Geller’s work, which thrilled him, and Gorst was the first person he saw.) Gorst introduced Cook to Jonathan Pearlroth, who arranged for Cook to visit the house with his sons. “It was a complete and total wreck, boarded up with plywood,” Cook says. “But it’s so playful. The boys totally got it.”

Eventually Cook designed what he calls Pearlroth II. His “number one priority,” he says, was to create the best possible setting for Pearlroth I. Though the new house separates the Geller building from the beach, its central void will give the old house ocean views. And the back of the new house is screened by oversized cedar shutters; in their closed position, they form a continuous, neutral backdrop for the Geller building. Cook also gave a lot of thought to the distance between the two structures. The Geller building is “sculpture in architecture,” he says, “and sculpture is in part formed by the space around it.”

The only catch, for both environmentalists and those who think historic buildings should be used as originally intended, is that these days, a house built in the 1950s is more likely to be seen as a pool house, a guesthouse, a pavilion, or even a folly, rather than an actual house. (The new residence is more than six times as big as the old one.) But if Geller’s building has been repurposed, it has also been renewed. “As happy as we are to have the big house,” Pearlroth says, “the star of the show is the diamonds.”