Renovation Award of Excellence: Hudson Commons, New York City
Kohn Pedersen Fox Associates, New York City
Cove Property Group, New York City
Vertical Expansion with Seventeen New Floors of Steel
The developers of Hudson Commons opted to transform what was initially a drab eight-story commercial building into a sleek office tower—and a case study in complex vertical expansion. Built in 1962, the existing cast-in-place structure was originally designed as a warehouse, and the base structure is comprised of two-way concrete slabs on a 24-by-28-foot (7.3-by-8.5-meter) grid, with drop panels, “mushroom” capitals, and a masonry core. To add to the appeal of a retrofit, the conversion from warehouse to office helped minimize the upgrades that would need to be implemented to the existing base building, and the unused zoning area was further capitalized upon through the addition of a vertical addition.
To accommodate the load from an additional 17 floors of steel, existing columns were retrofitted with new concrete “jackets.” To mitigate the difficulties of forming and casting within the confines of an existing environment, the new jackets were cast using shotcrete, as opposed to traditional methods. A new reinforced-concrete core was threaded through the building from foundation to the top of the structure, articulating existing columns, which helped meet the lateral demand of the new larger structure.
Demolition for the new core was done by reinforcing the existing slab around the area to be demolished, with some of the steel becoming part of the permanent structure. This permitted a shoring-free demolition, accelerating the schedule and cutting significant costs. The existing roof was reinforced with structural steel to accommodate a new, heavily landscaped amenity area, and the ground floor was lowered by over 2 feet (600 millimeters), yielding a generous new lobby space.