Within the next few weeks, the scaffolding surrounding the exterior of the Baptistry will disappear. So also will the plastic barrier separating the interior of the Baptistry from the main body of the church. It has been a long project that involved substantially more work than initially envisioned. That is both the bad news and the good news. The decision was made early on in the project to utilize the expertise of two preservationist engineers skilled in stone reconstruction. Ultimately that led to the discovery of a number of hidden defects within the tower that went undetected by an earlier "envelope" study of the church's exterior condition.
One of those hidden items was the discovery of some rotting timbers in the left side roofing of the tower itself. The repair required the stripping of the roof tiles and a reconstruction of a portion of the underlying wood substructure as well as the replacement of an extensive portion of the lead coated copper 'through-wall' flashing between the tiles and the granite tower.
Another discovery related to work done to the tower in 1991, which affected several areas of the membrane and resulted in water seepage and the need to do a partial replacement. The membrane was actually trapping moisture behind it, thereby facilitating the movement of moisture within the wall to the interior of the Baptistry. The water was, in effect, leeching through the stone facade of the interior walls, resulting in extensive water infiltration and the blistering of the interior painted walls of the Baptistry.
Extensive high pressure water testing of the exterior of the tower revealed that the mortar joints between the granite and limestone blocks needed to be replaced since this was another major source of water infiltration. All of the mortar had to be removed to a depth of approximately 4 inches and each of the interior surfaces of the stone cleaned so as to create a positive bonding surface for the new mortar. This aspect of the project proved to be the most labor intensive. All of the mortar was mixed in a controlled setting according to a specific formula recommended by the preservationists. In addition, the new mortar had to be applied in a three phase operation. The first "lift" was applied to the deepest third of the cavity to ensure a solid backing for the next two separately applied courses of mortar. Each of the "lifts" could only be applied after the prior lift had cured and the surface areas cleaned once again.
The water testing also revealed two significant problems with the stained glass windows. The packing material surrounding the windows used to hold them in place within the limestone blocks had deteriorated so much that water was freely entering the Baptistry during heavily driven rains. Additionally, once the windows were removed to address this issue, it was discovered that the lead frames were actually too small for the opening within which they were placed. This necessitated having to add additional lead to the perimeter of the windows so as to create a better fit within the limestone channels.
Father Bob getting a bird's eye view of the work site:
