Floor Slabs on Grade

Super-storm Sandy impacted many buildings, including 92 Laight Street, on the west side of Manhattan with tremendous groundwater hydrostatic pressure that caused cracking to occur in foundation walls and floor slabs on grade.  In this particular building, the new electrical conduit feeds were installed within floor slab trenches to protect them against any future storm surge. However, groundwater found its way to the area where the cellar level concrete floor slab trenches were dugout, waterproofed and re-patched with new concrete. The groundwater infiltration was witnessed at the cold joints where the trench cutouts met the original floor slab, as well as in all of the cellar level rooms where the trenches existed. The Compactor Room, the South Tenant Room, the Electrical Service Room, and the Hallway outside of the Electric Service Rm. have a raised floor slab on top of the trench locations. The hallway between the Compactor Room and the center Tenant Storage Room was also demonstrating an active flow of groundwater at the surface of the floor slab (where one side of the trench cut-out meets the original floor slab – small opening in floor).

In order to correct this groundwater intrusion problem, CGI utilized the unique water-like viscosity of its two-component, hydrophilic waterproofing system along the cold joints of the floor trench locations by drilling holes for the injection to a depth of 4 inches (to twist in our injection tools), so as not to compromise the waterproofing membranes within the trenches any further. Consequently, the compromised waterproofing membranes were sealed with the resulting gel.

After an intense and comprehensive injection waterproofing program whereby these floor slab trench cold joints were addressed with the CGI waterproofing system, the groundwater intrusion was remediated allowing building management to continue with the rebuilding construction program with the aftermath of the super-storm in the cellar level.

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