What goes wrong with slate roofs?
Typically, problems with a slate roof can be traced to one of four factors. • All slate is stone, but not all slate is the same. • Flashings fail. • People walking on slate roofs damage them. • Bad workmanship plagues many. (Photos: Bad repairs can be found on almost any old slate roof. Some constitute “hidden leaks,” such as #1 below, where a nail has been driven into the top of the slot, caulked, then the caulk has worn off leaving an almost invisible hole in the roof. A bib flashing would have prevented this problem and will still solve the problem if inserted at this time. #2 illustrates the same problem, this time with roof cement rather than caulk. #3 shows “face nails” that have been tarred over — these are guaranteed leaks. #4 illustrates two obvious errors: wrong type of replacement slate and exposed roof cement. #5 is another example of a multiple error — face nails, wrong type of slate and wrong shape of slate. All of the above can be removed and the roof properly repaired.
