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A VERTICAL VENTURE: 520 Madison Avenue - STO Building Group
520 Madison Avenue, positioned in the heart of NYC Midtown, the famed Plaza District has long been one of Manhattan's most sought-after commercial neighborhoods. Click to learn project details.
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Madison Avenue

A VERTICAL VENTURE: 520 Madison Avenue

Perfectly positioned in the heart of Midtown, the famed Plaza District has long been one of Manhattan’s most sought-after commercial neighborhoods. But trendy downtown developments and sleek skyscrapers taking shape on the far West Side have sparked a shift in this prestigious area. The towers that line the streets of NYC’s most expensive office market are raising the bar to compete with the flashy high-rises popping up throughout the city—and real estate giant Tishman Speyer is leading the way at 520 Madison Avenue.

Built in the 1980s, 520 Madison offers premier office space in a prime location, but as part of a larger initiative to revamp a few of their well-established properties, Tishman Speyer set out to create more commercial space at the top of the 43-story building. To make room for tenants on the 42nd and 43rd floors—plus a 2,200sf landscaped terrace—the mechanical equipment room (MER) on the 43rd floor needed to be relocated to the roof and elevator access had to be extended to the top level. Tishman Speyer brought on the Structure Tone team to help lead the way, but before they could get to work, they needed a dynamic approach that could get the job done within Tishman Speyer’s tight timeframe.

Detailed design. Designing this complex concept took over 15 iterations of scaffolding drawings—each of which was reviewed by Structure Tone, the steel and scaffolding contractors and two engineering teams. The primary engineer monitored the loads this 60-foot framework would impose on the building, while the third-party engineer proofed the design.

Swift winds. To ensure the scaffold was designed for the correct windspeeds, the team enlisted a firm that specializes in wind modeling and forecasting. The company built a scale model of the building, scaffold and every building within a 1,600ft radius. After testing the model in a wind tunnel, they concluded the design should be enhanced from the 110mph winds specified by New York City code to withstand winds of 130mph.

Hanging hazards. Demolishing the façade around the top floors meant the crew was breaking and removing thousand-pound slabs of granite with only the scaffold separating the huge stones from the street below. The team came up with a process to secure and test each slab, so they couldn’t slip before or during removal.

Unpredictable weather. Any rain, snow or winds exceeding 30mph meant all work on the scaffold came to a halt. The team analyzed two weather reports per day and prepared for weather events up to five days in advance. Before and during snowstorms, extra laborers came in to scatter ice melt and monitor the site overnight. When the storm was over, more laborers came in to help shovel the scaffold and work areas on the roof. The roofers even used their butane torches to help melt the snow.

We tried to plan for everything,’’ says Ron Pennella, Structure Tone project manager. “So, when we ran into challenges along the way, we were able to stay on schedule.

etting materials and equipment to the jobsite also required some creative problem-solving. The only way to transport the necessary components to the roof was through an 8ft-deep freight elevator in the basement—meaning all elements had to come in at 7ft, 11in. Once on the top level, each piece was hooked onto a trolley beam, wheeled out of the freight car and lowered into place.

“The size and weight of the components were critical,’’ says Pennella. “Everything had to be brought in and erected by hand with a tremendous amount of care.”

That level of care extended to the mechanical equipment room migration as well. At 8,000lbs a piece, lifting the elevator motors to the 43rd floor in an occupied building required extensive research and communication between the project team and building management. To move the equipment without disturbing tenants, the team cut a 10x10ft hole in the roof and built a temporary, waterproofed structure from the scaffolding over it. Then, they installed a chain fall hoist and gently lifted the equipment from the 43rd floor to its new location on the roof.

Though the migration went smoothly, punching a hole in the roof triggered a series of unforeseen air pressure-related issues known as the stack effect. Fairly common in high-rises, the stack effect refers to the difference in outdoor and indoor air pressure that can cause a building to act like a chimney—all the heat rises to the top in the winter and vice versa in the summer. In addition to affecting temperature regulation, the stack effect can disrupt the way elevators operate. Thankfully, there was a simple solution: windows! The team cordoned off areas with temporary walls and opened the windows on select floors to relieve the pressure.


Matching the building’s new façade to the original was a concern from day one. The stone used for 520 Madison’s façade was sourced from an open-pit quarry that shut down years ago. Determined to find a match, the team connected with the quarry owners in South Dakota, who found stones that had been quarried 37 years ago. Those slabs were shipped to Canada to be cut and finished, and then to New York to see if they’d match the existing façade. As it turns out, those blocks were part of the batch quarried for 520 Madison’s original exterior in 1981—Tishman Speyer’s very first development.

Ultimately, thanks to an amazing team effort, this phase of 520 Madison’s was delivered three months early, within budget and without a safety incident. “From the inception of the bid, Structure Tone had the most dynamic approach and the right team to tackle a project like this,” says Mucci. “I don’t think there are many other firms in the city who could have done what they did.”

Project Details

Size: 20,600sf

Client: Tishman Speyer

Architect: MdeAS

MEP Engineer: AMA Consulting Engineers, P.C.

Consulting Engineer: Thornton Tomasetti

Structural Engineer: Active Design Group

Wind Consultant: RWDI Consulting Engineers and Scientists

Sector: Commercial

Completion: January 2019

© Images courtesy of John Baer Photography.