01
Diagnose masonry and roof separately
Open joints, porous caps and failed counterflashing can each admit water. Interior staining alone does not identify which component failed.
02
Protect slate during masonry access
Scaffold, lifts or roof platforms should prevent concentrated loads and falling mortar. Covering must not trap abrasive debris against the slate surface.
03
Sequence counterflashing correctly
Base or step flashing and masonry counterflashing must overlap in the right order. Repointing around old embedded metal without a complete flashing plan can lock in a failing detail.