Parametric design and the geologic processes that formed the rock bluffs of the Puget Sound region may seem unrelated, but Seattle-based NBBJ senior associates Sarah Steen and Daniel Cockrell believe the processes share a—relative—independence from human hands. In creating a feature wall that abstracts the bluffs for the third-floor lobby renovation of the 56-story Two Union Square, also in Seattle, Steen says the designers aimed “to use technology in an unpredictable manner,” similar to the way tectonic activity is uncontrollable by humans.
The office tower, designed originally by NBBJ in 1989, features a curving reinforced concrete building core, which had been finished in a faceted wood veneer. NBBJ wrapped the core on the building's third floor in approximately 1,650 curved panels of pale travertine—selected due to its lightness in both color and weight—which were quarried and custom fabricated by the Poggi Brothers in Tivoli, Italy.
Because of the lobby’s prominence as the pinnacle of a grand staircase leading from the building’s first- and second-floor entrances, the architects saw a need for a focal point. “It just begs for something cool to be happening,” Steen says.
Instead of a surface treatment, the design team “started experimenting with something that could be part of the wall,” Steen says. They envisioned a sculptural element inspired by the geologic history of the Pacific Northwest, “sharp and angular with peaks and valleys.”
Using Grasshopper and Rhino, the NBBJ team established a set of parameters that would maximize the number of triangular sizes and shapes in order to keep them as irregular as possible. Next, they “allowed the script to connect the dots and create this network of angles,” Steen says. “That’s how we arrived at the patterning.”
The result is a nearly 20-foot-tall by 20-foot-wide 3D sculptural ribbon of 415 fractal panels that cuts diagonally across the wall plane like a mountain range. (A smaller tectonic wall feature arises near the elevator bank.) The angular stone panels emerge seamlessly from the more conventional coursing of the rectilinear wall panels, creating a monolithic central element that simultaneously feels divorced from its heft, floating above the floor. This juxtaposition is amplified by the natural banding in the stone, which was preserved meticulously by NBBJ working with the Poggi Brothers and local stonemason Synergism Stone. “It’s laid up on the wall as it [appeared coming] out of the Earth,” Steen says.
Ranging in thickness from 1¼ inches to 3¼ inches, the fractal panels are effectively pinned into place through pre-drilled holes in their top and bottom edges. The holes accommodate steel dowels welded to bent steel plates that are screwed into horizontal strapping, which, in turn, is secured to an 8-inch-wide stud wall covered with gypsum wallboard.
Though the concept of an abstracted cliff face came early, the final design required much refinement. “We did a lot of lighting experiments to make sure that we weren’t protruding from the wall too far and creating too many shadows,” Steen says. “And we did a lot of cardboard mock-ups [following the modeling]. We went analog.”
The light tests, conducted by NBBJ’s internal lighting studio, revealed that the panels, when positioned under overhead illumination from a recessed light cove, only needed to rise a maximum of 2 inches outboard to achieve the desired relief. This was fortuitous since the existing structure had to bear the additional dead load of the travertine panels.
Other design considerations came from the material restraints of the stone. The most significant deviation from NBBJ's 3D model followed the construction of a full-scale mock-up in Italy, working with the Poggi Brothers and Synergism Stone. Some triangular stone panel vertices chipped during installation. “We realized some of our acute angles were a little too fragile,” Steen says, “so we applied another parameter or two to control those acute angles.” Vertices had to be greater than 25 degrees and NBBJ specified filled travertine for panels with the most acute angles.
NBBJ ran a final mock-up with the stone on-site in Seattle, testing every aspect of the process, from fabrication to shipping to installation. Because the firm planned to preserve the natural coursing in the travertine, specific areas of the quarry were hand-selected to ensure the horizontal bands were consistent and not crooked. Even the rectilinear panels had to be precisely fabricated and labeled according to their position. “They had to be cut, labeled, crated, loaded, [and so on] all in the order” in which Synergism Stone planned to install the stone, which was from the top down.
It took 18 months to complete the overall lobby renovation, with Synergism Stone spending 15 months alone on the entire travertine wall.
The luminous end effect is testament to the team’s persistence. It’s critical, Steen says, to maintain “that clarity of concept and [continue] pushing for those big ideas when challenges arrive.”
