Award of Merit - Renovation

640 Fifth Avenue

The project team that renovated and redeveloped 640 Fifth Ave. in Manhattan needed to turn an 18-story building into a 21-story building without disrupting the office tenants or retail customers inside it.

The $38.3 million project involved constructing a three-story addition to the 267,000-sq.-ft. structure built in 1949 on the west side of Fifth Avenue between 51st and 52nd streets. The building now has 302,000 sq. ft. with standardized floor plates and common rentable floors. Tenants occupied the first eight floors throughout the project.

"It was a big job, well executed," said one judge.

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The project also involved extensive renovations. The project team stripped the existing exterior limestone façade from the 18th floor down to the 10th floor, and built and maintained a temporary protective roof for a full season. The team also completely renovated the lobby and added floor-to-ceiling windows, which provide views of St. Patrick's Cathedral and the rooftop gardens of Rockefeller Center.

The team also replaced and relocated the building's mechanical and electrical equipment in a phased sequence, while keeping systems for the occupied floors operating.

The project team had its work cut out to not disrupt tenants in the building or pedestrians on the busy surrounding sidewalks. That added to the complexity during all phases of construction, such as the steel structure erection, installation of the glass curtain wall, construction of the temporary roof at the 10th floor, reinforcement of steel columns, and replacement of windows. One solution the team developed was eliminating hoist delivery of materials to the upper floors. Instead, the team used the tower crane on site for structural steel erection.

Similarly, the team carefully managed elevator renovation. It maintained the existing service while reconditioning the cabs on four low-rise elevators by programming a different sequence and focusing on one elevator at a time. For the renovation and extension of the four high-rise elevators, the project team demolished half of the existing elevator machine room and brought two of the new shafts through it, while keeping the other two operational for construction personnel. It repeated the process in the remaining half of the elevator machine room for the last two elevators.

Another aspect of the renovation involved installing new cooling towers and a water tank. The project team erected the new towers and tank above the existing ones, built the new three-story addition around them, tied in the new equipment, and then removed the old systems.

Crews erected the steel by cantilevering a Gantry tower crane out from the existing base building at the 12th floor on a steel platform. While the approach required the team to reinforce the building in certain locations to support the new load and crane, it also allowed full completion of each floor as the steel went up.

The team also installed diagonal bracing, which transferred the new load to the building's center core. This approach - devised by the structural engineer - involved welding a new steel plate at the flange to reinforce and strengthen each structural steel column to carry the additional load of the new upper floors.

"It was a total change in use with major building upgrades," said a judge.