Author(s)

M. Farmer & F. Peters

Abstract

This project involves one of the largest cathedrals in the United States. Built in the 1950s, the exterior walls are limestone-faced brick masonry bearing walls. The roof structure is composed of reinforced, cast-in-place concrete slabs, joists, and beams, decoratively painted and exposed to the interior. The roof structure is supported by 14 limestone-faced masonry arches – the arches are approximately 30 inches thick. In 1972 a limestone fragment fell from a 90 foot high limestone masonry arch to the Sanctuary floor. Our investigation revealed that concerns regarding limestone failure were initially raised 10 years after the original construction. It was determined that control joints in the concrete roof structure were located directly over the arches, and the concrete members were placed directly in contact with the limestone arches without any ability for the arch masonry to accommodate the inevitable volume changes and movements of the roof structure. These differential movements between the concrete structure and the limestone arches have caused substantial damage to the limestone masonry and the concrete roof structural members, threatening the overall stability of both. The objective of this project was to stabilize the limestone arch masonry and reduce the potential for future distress by disengaging the roof structure from the arches to the greatest extent possible without critically compromising bearing of the roof structure on the arches. This challenge led to a series of targeted modifications to the concrete roof structure to overcome the damage it has sustained, and stone masonry repairs to isolate the roof structure’s influence on the arches. Keywords: cathedral, arch, roof, stone, concrete, joints, movement, structure, distress, repairs.

Keywords

cathedral, arch, roof, stone, concrete, joints, movement, structure, distress, repairs