Memorial Sloan-Kettering Cancer Center

Building a five-story rooftop addition over seven floors of Memorial Sloan-Kettering Cancer Center's existing seven-story main campus on the Upper East Side of Manhattan was anything but a run-of-the-mill hospital project.

Not only did the project team have to build atop a structure that was grossly inadequate to accommodate the enormous loads of an addition, it also had to complete the $99.48 million job without interrupting patient care.

"During the entire construction schedule, the hospital never lost a day of operation," a jury panel member said. "This was a tough assignment executed masterfully."

The project required five new fit-up programs, including a 78,300-sq.-ft. state-of-the-art operating suite, interoperational pathological accessioning laboratories, new pediatric day hospital, pediatric inpatient unit and a complex double-height interstitial mechanical platform to support this and future expansion.

To accommodate the loads of the addition, the project team decided to use a system of vertical trusses, called "supercolumns," that would penetrate the seven existing floors like four "table legs" and slice down through the building's existing structural floor slabs.

To support the supercolumns, new foundations and a 22-ft. pit for the elevator shafts had to be built below the existing mechanical subcellar. Specialized equipment and technologies, as well as innovative construction engineering and site logistics, were implemented on a daily basis.

To ensure that hospital operations were not disrupted, the supercolumns components were assembled, bolted and welded and floor penetrations were done during off-hours (typically overnight) within sound-deadened barricades.

After the supercolumn work was complete, the removed sections of floor slab were repoured, the barricades were removed, and all floor, ceiling and wall finishes were returned to their preconstruction condition. The supercolumns were never visible to hospital workers.

The structural and logistic challenges faced with construction of the supercolumns were not as great as those pertaining to distribution of the mechanical, electrical and plumbing systems.

The floors through which the supercolumns were constructed were built as four or five separate structures, so proper documentation describing the MEP distribution did not exist. Furthermore, the supercolumns were placed in locations selected strictly for programmatic, functional and architectural reasons, not for optimizing MEP considerations. For example, on one floor the hospital's main power feeders needed to be rerouted around the column legs one by one.

The project team also faced a hurdle in architecturally and structurally integrating the addition with the existing building to convey the impression of having been conceived and constructed as one holistic, modern hospital building.

Despite the existing building's light-beige brick motif, the façade architect selected a cladding solution of a new custom-designed, sleek, translucent curtain wall system. This system would interplay the light and shadow effects caused by masking existing exterior masonry walls, existing ribbon-type window systems, new and existing mechanical louver systems and the new building's structural frame.