In the course of a conditions survey, it occasionally becomes necessary to get beneath the surface to find the cause of problems. Conducting probes helps us understand a building's construction better and in some cases shows problematic variations from the intended design.
The roof of St. John's Chapel at the Groton School is probed in this picture to check the condition and design of the original roof decking. Underneath the slate is rubber flashing, yet the rubber flashing does not extend to cover the entire roof. The limited coverage of the rubber flashing allowed considerable leaking on the existing roof. The membrane seal to copper gutters is a weak roofing system; it was allowing water infiltration into the walls and accelerating the deterioration of the limestone.