Erroneous Design Assumptions and Construction Defects in a Thin Stone Facade System

Abstract

Abstract During a routine close-up facade inspection of the exterior walls of a 15-year-old, 31-story office building, a loose 30-mm thick granite panel was discovered. Initially, it was believed that this movement was due to the location of the anchorages relative to the panel geometry. A more thorough examination of the panel was performed by inspecting the panel attachment from the interior of the building. This inspection revealed that one of the two epoxied wind load anchors had failed. An extensive investigation of the granite facade panels, including additional close-up exterior and interior inspections, structural analyses, and testing, was undertaken. Interior examinations revealed construction defects in the epoxied anchors. In addition, the structural analyses indicated a flaw in the original design that affected certain panels in high wind load zones. Repairs were designed to address the design and construction deficiencies. Supplemental panel anchorages were installed from the exterior of the building, thereby minimizing disruptions to building occupants. While the implemented panel repairs can be identified at close range, they are imperceptible from publicly accessible vantage points.