Investigation and Repair of Structural Deficiencies in Projected Masonry Bay Construction

Projected masonry bays are a common feature on many historic buildings. Over the course of the last 100 years or so, bays have been constructed utilizing a wide variety of masonry and framing configurations to provide structural support to these eccentric architectural elements. Mechanisms to resist the natural tendency of the bay construction to “sag” and/or rotate away from the plane of the wall have historically included corbelled and/or cantilevered masonry, steel tension ties, counterweight beams, and a variety of steel, concrete, and wood framing configurations. Many of these support system mechanisms have satisfactory in-service performance, whereas others have been found to permit undesirable behavior. Unanticipated flexibility in the bay support may result from improper interaction of the various structural components. Distortion of the bay construction leads to distress, premature deterioration, and sometimes failure within the bay assemblies. This paper will present a case study pertaining to the investigation, analysis, and repair of a projected masonry bay system involving several different support mechanisms and will focus on a specific structure in which effective support assemblies were integrated into the existing building fabric.