Award of Merit: High-Rise Category
Buttress and Exterior Façade Repairs of Alice S. Millar Chapel
Northwestern University, Evanston, Illinois
Submitted by Building Technology Consultants, PC
Building Technology Consultants, PC
Arlington Heights, Illinois
Bulley & Andrews Masonry Restoration, LLC
Northwestern University’s Alice S. Millar Chapel was originally constructed in 1962. The exterior façade of this religious facility is clad in lannon stone, buff limestone, and bluestone. Full-height 60 ft (18.3 m) tall buttresses constructed with common backup brick are located at each corner of the building and intermittently along the east and west elevations.
Significant deterioration of mortar joints and displacement of lannon stone at several buttresses prompted a façade evaluation. Buttress deterioration was attributed to severe freezing-and-thawing damage of the backup brick masonry. During the evaluation, additional façade distress, including cracked individual lannon stones, deteriorated sealant joints, and open mortar joints at wall areas between buttresses, was noted. The condition of the exterior walls and buttresses allowed a significant amount of water into the mass wall system.
The primary project objectives were to rebuild portions of deteriorated buttresses with durable freezing-and-thawing-resistant materials and limit the amount of water that could penetrate through the exterior façade. After assessing the structural contribution to the lateral load resistance of the buttresses, repair details and specifications were prepared to address the observed deterioration and water penetration.
During construction, several hidden conditions were uncovered that required repairs. Details were developed and these conditions were repaired to reinstate the structural integrity and water penetration resistance of the buttresses.
Due to the complexity of the project, close coordination between the owner, contractor, and engineer was necessary. Technical challenges during construction required expeditious decisions to keep the project on schedule. Now that the buttress and masonry repairs have been completed, the owner is planning to restore the interior chapel wall surfaces during the summer of 2011.