Tag: preservation

How the Domes Got Tiled

E013 july 1956 dome 2Parish-led renovations in the 1950s looked good at the time, but changed an historic church.

Contractor Charles Kain recalled a long-ago project at St. Francis de Sales Church in Philadelphia: “Early in the 1950’s we were approached by Bishop Joseph McShea,..the pastor…, to resurface the domes. They were quite old, in poor condition, and leaking into the church…The Bishop was proud of the fact that the domes could be seen as part of the skyline from a distance in the city on the highways going north and he wanted to maintain the character of the domes as they existed…We assured him that we could renew them with ceramic tile.

We consulted a tile contractor, Belfi Brothers, with whom we had done work previously. They advised us that the common bathroom tile was not sufficiently durable under exterior conditions and directed us to a tile manufacturer in upper New York State who made the type of exterior tile which would be appropriate. Next, I performed the structural calculations necessary for a domed structure. We determined that we should leave the existing dome in place to serve as a base for the superstructure, cover this with a four-ply fabric and pitch roofing membrane for waterproofing, then place a 3-inch thick reinforced concrete layer to accommodate the loads of snow and wind, then install the finished tile layer. We also divided the surface into eight quadrants, designed artistic patterns similar to those in the existing dome, and used a herringbone pattern for installing the tile.

The old dome had a base structure of masonry tile which was adequate to carry the necessary roof loads. One question asked was how this structure could carry the additional loads of the new concrete and tile. We explained that the old structure would have to carry the added loads only on a temporary basis until the new concrete dome on top could harden and become the basic supporting structure of itself and the normal roof loads…When we presented our design… to the Bishop, he…called upon…a structural engineer…to re-check my calculations…The Bishop…had previously read Latin descriptions of how some of the Roman domes were constructed…this confirmed his approval of our work.”

In the process of construction…we designed a small steel frame to roll around the dome on wheels at the base and at the top, enabling the workmen to reach all areas of the dome. For the exterior tile work, the tile setters, accustomed to placing tile on bathroom walls, had to experiment to get the flat tiles in a herringbone pattern on a spherical surface. Obviously, they succeeded.”

Fifty years later, when the joint between the big dome and the lantern at the top leaked, and the veneer of modern tiles peeled off, Annabelle Radcliffe-Trenner and her team from Historic Building Architects were called in to study the original Guastavino dome underneath – a unique historic structure not understood by the 1950s parish contractors — and the engineering complications created by the 1950s concrete overlay. After considerable research and consultation with a variety of experts, they determined that the best available option was to remove the hazardous modern tiles and confirm that the 1950s concrete was working well to prevent water leakage. The simplest and cheapest solution was to paint the concrete dome to match the original dome tile colors. Paint samples were tested and left in place for several years and they did very well. However, a different paint product was ultimately used and that has not adhered to the concrete and has faded over time. It’s under warranty. We’re working on resolving issues and hope to get the dome repainted in 2020. So, as St. Francis de Sales himself once said: “Let us await our advancement with patience.”

 

 

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The main dome with the 1950 tiles, as it looked in the 1990s.

A000 aerial view

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