Bruce Damonte

For the design of the New York office of Pinterest, Evan Sharp, the co-founder of the online idea-discovery and cataloging platform, suggested that San Francisco–based IwamotoScott Architecture seek inspiration from the New York Public Library’s (NYPL’s) Picture Collection. In a sense, the library's archive of more than 1 million print images is “the analog version of Pinterest,” says principal Lisa Iwamoto. “It’s like a walk through visual history.”

Beyond the collection, one aspect of the NYPL's 1911 Beaux-Arts building in particular caught the firm's eye: the crisscrossing internal stairway designed by John Merven Carrère.

Pinterest’s office, located on the fourth and fifth floors of the building directly across Fifth Avenue from the NYPL, needed an element of vertical connectivity. “To have to [take] the elevator to go up one floor is not the culture that they’re trying to create,” Iwamoto says. “They want a culture where people are flowing through the space seamlessly.”

IwamotoScott, which also designed Pinterest’s San Francisco headquarters, conceptualized a scissor stair that could be approached from opposite directions with each stair run meeting at a central landing. Working with the layout of the building’s existing structural bays, IwamotoScott with New York–based Spector Group sited the stair at the office’s center to maximize accessibility and its significance.

Intentionally oversized at 5.5 feet deep and about 14 feet wide, the landing encourages organic interactions among employees as well as serves as “an architectural reference” that Iwamoto says resonated with the client “just like it resonated for us.” However, a stair that is too open can also create acoustical distractions, she says. “We didn’t want a big hole in the floor. We wanted to enclose it somehow and yet not enclose it so that it was a tunnel. It needed to be porous too.”

The designers decided to wrap the steel stair structure in a series of vertical and horizontal white-ash fins, creating the effect of a wooden box that’s been parsed into rectangular cross-sections. The perpendicular fins provide a degree of transparency and limit visual and acoustical disruptions to or from adjacent workspaces, while the wood, also used to finish the stair treads and landing, adds warmth to the space. Pragmatically speaking, wood was also a much lighter option than metal fins, adds principal Craig Scott, AIA.

Bruce Damonte
Bruce Damonte

The fins follow the ascent and descent of the stair runs, creating a telescoping effect and the illusion of two intersecting volumes, 20 feet long by 16.5 feet wide and 20.5 feet tall, floating in the office. “It was really important for us that it form the heart of the space, and that as you were walking around the space, you would naturally gravitate toward this sculptural element in the middle,” Iwamoto says. The fins also exaggerate the intersection between the two volumes: The horizontal fins overhead overlap with the complementing fins of the adjacent stair above the central handrails rather than bypassing one another. “That was probably one of the more complicated moments,” Iwamoto says.

IwamotoScott modeled various iterations of the stair’s opacity in Rhino and worked with New York–based millwork company Miller Blaker and Englewood, N.J.–based steel fabricator Burgess Steel to build a physical mock-up. The team ultimately specified 42 wood fins 6.25 inches deep and 1.625 inches thick, spaced 5.5 inches on center. Because nearly every piece of wood is unique in length, aside from its twin on the opposite stair, each fin had its own CAD file, says Steve Samuels, the project manager for Miller Blaker.

Ranging between 11.5 feet and 13.5 feet long, the vertical wood fins were fabricated as separate L-shaped pieces and “clam-shelled” together over vertical steel plates, which are welded to the steel stringers. The solid horizontal fins, approximately 5.8 feet long, lock into the vertical fins via mortise-and-tenon joints to span the width of the stair. The 5.5-inch-long tenons are secured with specialized knock-down fittings and glued.

The fins are anchored to black steel stair stringers, which tie into the main building structure at the fifth floor. Much of the stair, including the central landing, is hung from the beams of the floor above them via what Iwamoto describes as steel stirrups: “The default thing to do would be to put the landing on posts, but we didn’t want to do that.”

The topmost horizontal beam also ties into the ceiling beam via a pair of L-shaped metal plates. To prevent the fins from swaying or sagging, 0.25-inch steel cables run through both the vertical and horizontal fins. “The ends of the cables were tightened within the body of the cross-beam, and the holes were plugged,” Samuels says.

Even with a mock-up for reference, Samuels says the steelwork was checked regularly for accuracy. “The tolerances that we had to work with in order to maintain the gap between each rib were pretty small,” he says—as tight as 0.1875 inch. If the steel wasn’t perfectly plumb, it put unnecessary tension on the wood, which relies on the steel for a certain amount of its structure. “Even within that, there was a lot of shimming that we had to do inside every clam-shelled piece to make sure our pieces were perfectly plumb even if the steel was not.”

Completed in 2016, the scissor stair has become both a functional centerpiece and means of vertical communication. “It’s like a crossing of paths,” Scott says. “When you go up either run or down either run, you have a choice of two ways to proceed.”