A significant aspect of Phase I was the replacement of the main upper roof over the nave, transepts, and apse.  The original roof was determined to have been a standing seam sheet metal; most likely tin-coated wrought iron, which failed early on. Consequently, the roof was replaced with slate in the 1870’s, and the crenelated parapets were later removed in 1938.  Removal of the gutters and crenelated parapets at the eaves allowed water to run over the clerestory walls and windows, accelerating deterioration of these elements.

Analysis of the roof replacement options concluded with the recommendation to install a sheet lead roof and gutters, and to reconstruct the crenelated stone parapets.  Lead roofing was recommended because of the similar appearance to the original tin plated roof and for its proven longevity.  Consultation with lead roofing expert Stan Halls, from the United Kingdom, was conducted to ensure proper detailing and installation. The replacement of the main upper roof was completed in the summer of 2004.