No. 9 Walton is a luxury condominium high-rise in Chicago’s elegant Gold Coast neighborhood. The 500-foot-tall tower boasts a long list of amenities, including an indoor pool and spa, wine cellar with private wine storage and covered dog-run terrace. While no two floors are completely alike, each 4,400-square-foot condo unit includes a 360-square-foot terrace.
Tribco provided the full concrete frame with all materials, labor and the tower crane for this residential condo tower, ultimately supplying and installing more than 23,000 cubic yards of concrete, 1,900 tons of rebar and 237,000 pounds of post-tensioning cables.
The Tribco team used a post-tensioned (PT) flat-plate slab concrete structural system for the tower with a large tube shear core wall for the central elevator. The structural system is ideal for a building containing spacious residential units with unobstructed views of the city—including 18-foot ceilings at the penthouse levels. Flat PT slabs maximize the amount of usable space and window sizing while keeping the overall structure height lower and adept to the Chicago winds.
Adaptability and coordination
Walton No. 9 was a unique project not only because of its luxurious floor plans and finishes, but also due to the need for frequent last-minute coordination. The project included more than 30 structural drawing bulletins, 80-plus architectural drawing bulletins and nearly 300 concrete requests for information (RFIs) due to the customization needs of the condo buyers. Several floors were added to the building design after foundation work had already begun. To help accommodate loading for the additional levels, several post-tensioned levels were converted to lightweight concrete. Nevertheless, Tribco’s quick-acting project team and field crew worked in tandem to help guide the project to a successful close without notable quality issues.
Tribco engineers leveraged Revit BIM software to model all concrete geometry changes. In-house shop drawings were updated and often electronically sent to the field within the same day as receiving the design changes. More than 3,000 embedded items were modeled to find clashes between precast facade, window and mechanical embeds so adjustments could be made in advance without delaying field operations.
A tight urban site
The tight quarters of most city center project sites require careful planning and consideration, and No. 9 Walton was no exception. The Tribco project team engineered and coordinated a temporary leave-out in the second floor to allow concrete trucks to deliver concrete inside the footprint of the first floor and above the subterranean levels. Tribco’s construction plan accounted for ready-mix trucks delivering loads as well as the need for the trailer pump to convey the mix to the upper floors.
With the building footprint directly abutting a historic church to the west, the pool deck of the neighboring 2 West Delaware building to the south and an elementary school across the street to the north, concerns about falling debris were incredibly important. Tribco used a perimeter safety screen to stop any loose debris from falling from active construction floors, protecting workers and the public alike.
Since its completion in 2017, the project has become an elite address to call home. Residents have included Chicago finance and industrial tycoons as well as several star athletes from almost every major Chicago sports team. This building broke housing sale records when Ken Griffin bought the top four floors for $58.5 million.