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Precast Approach Revives St. Mary’s Hall at Boston College

| August 24, 2016
St.Mary's Hall, reopened after major renovations and restoration. Detail of main entrance facing Linden Lane.

St.Mary’s Hall, reopened after major renovations and restoration. Detail of main entrance facing Linden Lane.

St. Mary's Hall, following its complete restoration.

St. Mary’s Hall, following its complete restoration.

Need dateline – St. Mary’s Hall, opened in 1917, had a distinguished pedigree but was showing its age. The ornate, Collegiate Gothic four-story building was constructed of Roxbury Pudding Stone with precast or cast-stone decorative elements throughout. But after nearly 100 years, these pieces — which were not well understood or engineered at the time — had begun to fail. To rejuvenate the hall, designers used precast concrete elements to recreate the ornamental pieces.

“A key design challenge was faithfully replicating the appearance of the original cast-stone details while improving the long-term durability of the masonry construction,” explains Wendall C. Kalsow, preservation architect on the project. But the project’s scope was daunting: There were more than 50 pieces of significant “museum quality” sculpture and more than 16,000 total precast units.

Each piece was surveyed, evaluated, and given a unique number with specific dimensions before shipping it to the precaster. Damaged pieces were rebuilt by the precaster’s mold team, and molds were constructed to fabricate new pieces. A high-density liquid resin ensured precision and the proper textural finish. Each piece was molded, cured, unmolded, and treated with a light acid-etch.

Two precast concrete mixes were used. One produced a granite-like granolithic finish for the building’s base, while a second mix replicated limestone. Stainless-steel reinforcements and plastic manipulation anchors added durability and long-term quality. The building was laser-scanned to digitally record benchmarks and to provide backup information needed during the reconstruction.

To save time and complexity, some of the smaller pieces were combined to create larger units with false joints. Most pieces featured a six cut-line finish executed in wet-cast, except for the 28 tracery windows. They each contained 17 pieces of cast stone, the complexity of which led to them being cast as one unit. Each was assembled from two precast sections in the plant, both cast with the visible face down to achieve the highest quality control.

The work represents the largest cast-stone restoration of a historic building in North America.

For more information on this project, read the article from the summer issue of Ascent magazine at http://www.pcine.org/st-marys-hall.

THE TEAM

Precaster: BPDL Inc., Alma QC, Canada

Precast concrete consultant: Building & Monument Conservation, Arlington, Mass.

Owner: Boston College, Chestnut Hill, Mass.

Designer: DiMella Shaffer, Boston, Mass.

Restoration architect: McGinley Kalsow & Associates, Somerville, Mass.

Structural engineer: LeMessurier Consultants, Boston, Mass.

Contractor: Shawmut Design & Construction, Boston, Mass.

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Category: All, Education