The Northern Trust Building, part of a revitalization plan in the South Loop, was set to be gutted, remodeled, and transformed into modular office space under new ownership. Built in the late 1960s, the structure featured 8-inch precast panels hung on a robust steel frame, giving it an imposing appearance that was both architecturally and structurally impressive. However, the window openings were small compared to today’s demand for expansive views. The renovation plans aimed to vertically "open" these existing window bays to accommodate larger glass panels, revealing breathtaking city vistas that had long been hidden.
Problem:
The challenge was to saw-cut and remove over 38 inches from each of the 365 reinforced 8-inch thick precast concrete panels, each spanning 27 feet. Three demolition contractors proposed cutting the panels from the inside, which would leave the building exposed to the weather for at least two days per bay, delaying temporary board-up installation. Additionally, the wet-spray and slurry from the cutting would halt all work except for interior demolition until all openings on a floor were sealed. With around sixty bays per floor and two days needed per bay, this approach would delay remodeling for at least four months, extending the project timeline by at least two years for six floors.
Solution:
P&G proposed an innovative solution for the precast demolition that kept the building secure and weather-tight, allowing other trades to continue interior work. Their design involved movable jacks in each opening after removing the existing glazing and aluminum framing. Three jacks per bay transferred the load from the precast panel above, enabling safe saw-cutting from the outside. Each 7,000-pound panel was removed in one piece using a portable rooftop hoist, reducing saw-cuts from over 30 to just three. This streamlined the demolition time from two days to about two and a half hours. An interior board-up system was installed at each bay to keep the window opening watertight during the removal, allowing for simultaneous interior work.
Despite the initial costs, P&G’s solution is estimated to have saved the Owner several million dollars and cut the project timeline by nearly two years.