Track 2: Materials over Time: Points of Change
Montreal Customs Building – Two Wings, Two Experiments in Construction
Tuesday, September 25
10:30 AM - 12:00 PM
Location: BNCC- 101BG
The Montreal Customs Building is an eight-floor Beaux Arts-style building taking up a complete city block in Montreal, Quebec. Built over two phases in 1912-16 and 1934-36, the building possesses a highly uniform façade of Stanstead granite and Wallace sandstone based on the original 1912 design by E.L. Horwood for both wings. The consistency of the façades nonetheless conceals heterogeneous structural systems and exterior wall assemblies, illustrating the early twentieth-century period of experiments in construction as steel and concrete structures gradually replaced load-bearing masonry in institutional buildings.
To illustrate that evolution in construction methods, this presentation focuses on the full-height projecting corner bays (avant-corps). It will compare the observed assemblies and deteriorations of both wings as well as the proposed remedial strategies.
The original 1912 wing is a hybrid building with a steel structure. Structural elements along the building perimeter are typically embedded in the brick backing of the stone-clad exterior walls. However, at the projecting corners, the wall thickness significantly increases to 2.2 meters (7 feet), forming eight floor-high load-bearing masonry components, mostly unsupported by the structural steel grid. Exploratory openings revealed that the brick backing is an alveolar assembly presenting numerous horizontal cavities, likely a deliberate attempt to reduce loads and costs during the original construction. The stone cladding presents large joints and significant deformation. These deteriorations are progressing despite past stabilization efforts to tie the cladding to the backing. Analysis demonstrated that the deformation may be the result of inherent vices such as the height of unsupported masonry, stone shapes, insufficient anchoring, and freeze-thaw sensitive interface between the backing and cladding.
The 1934 wing is a hybrid building with a concrete structure. Wall assemblies tend to be relatively thin compared to the 1912 wing. Most of the inherent vices observed at the 1912 corner bays were corrected in 1934. Nevertheless, the projecting corners of the 1934 wing present, to a lesser degree, deteriorations similar to those of the original wing. Exploratory openings revealed that, on most floors, the concrete structure is not tied to the corner masonry, leaving it unsupported over four to five-floor heights. Although this condition may not fully explain observed deteriorations, this issue has to be addressed as it does not meet current regulations, nor did it follow standard practices at the time of construction.
Remedial strategies were developed to improve the performance of the projecting corners of both wings and mitigate inherent vices, with low structural impact on adjacent areas that have performed well over time. Although the corner bays of both wings have a similar appearance and similar types of deteriorations, remedial actions differ significantly.
- describe the evolution of early 20th century structural and masonry envelope systems.
- analyze the behavior and deterioration patterns of unsupported load-bearing masonry over several floors.
- analyze the behavior and deterioration patterns of unsupported hybrid structure (masonry/concrete) over several floors.
- identify possible remedial actions for unsupported early 20th century masonry.