Built from 1921 to 1932, the Old Chicago Post Office is a nine-story limestone landmark groundscaper that is three city blocks long and a block wide. If stood on its end, it would be the equivalent of a 64-story tower. The Art Deco building was the city’s main hub for sorting as much as 19 million pieces of mail a day until 1997, after which it sat vacant for two decades. While vacant, the interior suffered extensive floor and interior damage due to roof failure. The building underwent an $800 million renovation, the largest historic redevelopment in the country, to convert more than 2.5M SF into a world-class multi-use office and event space with an innovative 3.5-acre urban rooftop oasis. As a historical landmark, the restoration was required to retain original design characteristics and aesthetics. The majority of the existing floor was concrete but renovation also included tile, carpet and wood in event and work spaces. Every crack, crevice, or hole throughout the 2.5 million square foot space had to be located, repaired, and brought to historic-appropriate appearance. The mixed-use structure preserves the original character of the building while creating a vibrant, functional space for work, dining, events, exercise, and recreation. The renovated Old Chicago Post Office truly bridges the city’s glorious past with its modern, dynamic future.
Unique Installation Challenge Strategy
The Old Chicago Post Office building was built above the city’s main rail lines to facilitate large volumes of mail passing through the institution. While functionally innovative, the structure is subject to constant vibration from railway traffic. Further, the raised structure, open at its base with its foundation above ground, is constantly moving and shifting. As a historic building, flooring also had to meet rigid aesthetic specifications. The renovation specified that flooring have no more than ½ inch surface fluctuation within a 10 foot area and that no significant weight be added to the building. Although a new topping could achieve surface specs, building movement virtually assured cracking. The unique solution was to allow existing cracks filled with custom color epoxy to provide necessary flex. The surface area would be raised or reduced to meet fluctuation spec and then polished or treated to meet historic aesthetic requirements. Each floor in each building (South, North, and East buildings) presented unique conditions that challenged the team and demanded extensive testing of solution materials, products, and installation techniques. With each challenge met, the team delivered floors that will withstand unique building characteristics while achieving historic aesthetics within a modern, functional mixed use development.