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520 Madison Avenue - STO Building Group
Structure Tone is a global leader in construction management and general contracting services with offices located in the US, UK, and Ireland. Founded in 1971, the company is among the world’s top twenty construction companies worldwide, responsible for more than $3.5B in annual construction volume.
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520 Madison Avenue

Built in the 1980s, 520 Madison offers premier office space in a prime location. To create more commercial space for tenants at the top of the 43rd floor—plus a 2,200sf landscaped terrace—the mechanical equipment room (MER) had to be relocated to the roof and elevator access extended to the top level. We were brought on to help create a dynamic approach that could get the job done within the tight timeframe.

Our approach consisted of constructing a unique scaffold system that extended down the building. To build safely on the roof at 570ft in the air, we prepared for every possible complication and designed the concept over 15 times, considering windspeeds, hanging hazards (including the building’s façade), and unpredictable weather.

Getting materials and equipment to the jobsite also required creative problem-solving. The only way to transport necessary components was through an 8ft-deep freight elevator. Once on the top level, we hooked each piece onto a trolley beam, wheeled it out of the freight and lowered it into place. To move the MER without disturbing tenants, the team cut a hole in the roof and built a temporary, waterproofed structure over it. Then they installed a chain fall hoist and lifted the equipment to the roof.

Though the MER migration went smoothly, putting a hole in the roof triggered a series of unforeseen air pressure-related issues known as the stack effect that can disrupt the way elevators operate. To combat this, we cordoned off areas with temporary walls and opened the windows on select floors to relieve the pressure.

Finally, matching the new façade to the original was a concern from day one. The stone used for 520 Madison was sourced from an open-pit quarry that shut down years ago. We connected with the owners, who found stones from 37 years ago. The slabs were shipped to New York to see if they matched the existing façade. As it turns out, those blocks were part of the batch quarried for the original 1981 exterior.


Tishman Speyer


520 Madison Avenue
New York, NY


MdeAS Architects


AMA Consulting Engineers

Structural Engineer

Active Design Group Engineering

Building Envelope

Thornton Tomasetti

Contract Type




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