Chicago Federal Plaza
The Chicago Federal Plaza in Chicago’s Loop district includes the John C. Kluczynski Federal Building and Loop Station Post Office, both designed by Ludwig Mies van der Rohe. The plaza is used often for community activities, such as protest demonstrations and a weekly farmers market. The General Services Administration (GSA) carried out a complete rehabilitation of the plaza in the early 2010s. GSA personnel observed displacement of the plaza’s granite pavers, particularly at drain locations, and became concerned about tripping hazards. SGH investigated the cause of the pavers’ movement and helped the project team evaluate remedial options.
The plaza’s pavers are set in a mortar bed over waterproofing on the concrete slab. SGH investigated the pavers’ displacement, which was reported primarily around the bi-level drains on the plaza’s north side and along the perimeter of the vault to the south. Highlights of our work include the following:
- Reviewing existing documents to understand the plaza’s design and configuration
- Conducting a visual survey to document the location and extent of displaced pavers
- Making observations at exploratory openings to document the existing construction
- Performing petrographic analyses of extracted mortar bed samples to determine the material composition and condition
SGH identified areas where water could not properly drain, saturating the mortar bed and leading to displacement of the pavers when the mortar experiences freeze/thaw cycles. We proposed several remedial options for the project team’s consideration and are proceeding with designing the repairs.