Unusual Failure and Repair of an Ornamental Limestone Entablature

The exterior walls of the subject three-story office building constructed in the 1920s are composed of multi-wythe clay masonry with a limestone facade and a decorative entablature at the roof level. A roof parapet sits atop a limestone water table that extends approximately 1 m out from the building facade. After multiple cracks, open joints, and spalls near the building corner drew attention from municipal officials and the local press, an investigation was undertaken to determine the extent and causes of the observed distress. This investigation revealed that expansive forces from the roof parapet, coupled with structural separation at a roof construction joint, likely led to the facade distress at the building corner. In addition, spalls and cracks on the underside of the limestone water table were attributable to improper roofing details. Repairs were designed to stabilize and remediate affected portions of the facade while minimizing the aesthetic impact to this historic structure. Lessons learned from the investigation of this uncommon failure and the subsequent repair designs are presented herein.