Courtesy of Morris Adjmi Architects

The view of New York City from this floating glass-and-steel aerie on the city’s West Side couldn’t be more majestic.

In the near-distance reigns the Empire State Building and the fabled NYC skyline. Closer in, the growing architectural wonderland of Chelsea. Below, the strolling paradise of the High Line. Imagine this crazy-beautiful view being walled-over to meet fire code.

Welcome to 520 West 20th Street, the latest architectural pearl on a string of them along the High Line from Morris Adjmi Architects. The firm’s portfolio of adaptive reuse projects reveals a sensitive hand at fusing historic integrity with contemporary design and materials. 520 West 20th Street is a classic example, essentially a stacked massing of new atop old in a beguiling vision.

Floating Three-Story Addition

The seemingly suspended new three-story steel addition is poised above an old 60,000-square-foot, four-story brick warehouse. The family-owned building is being reimagined as an 85,000-square-foot, seven-story mixed-use center, ideal for a corporate tenant.

“The historic integrity of the warehouse is preserved with the help of two new vertical cores that support the glass-and-still addition,” explains firm founder Morris Adjmi, FAIA. The cores work like “vertical masts to support the glass-and-steel box spanning between them.” The new addition is cantilevered, creating the illusion of a floating office complex to High Line strollers.

Courtesy of Morris Adjmi Architects

Transparent Firewall

The upper tier features floor-to-ceiling glass panels. As obvious as that transparency seems, it didn’t come without a knotty complication: The extreme proximity to neighboring buildings mandated two-hour-rated firewalls on the building’s flanks. Spanning the new addition with an 11-foot-tall glass ribbon seemed like a dim possibility.

“We discovered there were apparently no manufacturers of two-hour-rated fire-resistive glass in the sizes we required,” Adjmi says. “You could find smaller windows or create something with lots of mullions.” In fact, the solution Adjmi’s team had in mind would make 520 West 20th Street the nation’s largest installation of fire-resistive glass.

Unexpected Solution

Emphasize the word “apparently.” A California company came to the architect’s attention from the project’s chief glazing contractor. Contact was quickly made to Safti-First, North America’s only vertically integrated, single-source manufacturer of fire-resistive glass, framing, and entrances for over 35 years. Yes, their ASTM E-119–rated, fire-resistive SuperLite II-XLB 120 system met the fire code requirement. What about the oversized dimensions?

Good news … they could go even bigger. Lucas Posada, Adjmi’s lead architect on the project, remembers the feeling well. “It was amazing. The windows are custom-designed to just what we needed.” Having a maximum clear view area of 7,980 square inches with a maximum clear view height or width of 133 inches, SuperLite II-XLB 120 has the largest tested and listed sizes of any fire-resistive glazing product available today. The inclusion of low-iron glass in the fire-resistive glazing units also ensured superior clarity and aesthetic continuity with the adjacent non-rated windows.

Courtesy of Morris Adjmi Architects

Good to Go

There were no code issues, either. NYC code officials took one look at the third-party certifications from Safti-First and issued a quick approval. “There wasn’t even a question,” Posada recalls.

Like the acclaimed repurposing of the neighboring High Line, 520 West 20th Street is a stylish reminder of how adaptive reuse can be a superbly-realized melding of old and new.

To learn how advanced USA-made fire rated glazing systems, including jumbo-sized two-hour-rated fire-resistive glazing, could support your design, visit