Storm & Flood Damage Recovery in Princeton, NJ

Much of it does not, and applying it can do harm. Historic stone walls were built to breathe and to be damp, with lime mortars that tolerate moisture. Modern sealants and cement repointing trap water in the wall and push it elsewhere, often accelerating deterioration. The right approach manages water before it reaches the wall and uses compatible materials on the wall itself. It is worth engaging someone who works on historic fabric specifically.

That delay points to subsurface flow along the rock. Rain soaks through thin soil, reaches hard diabase, and travels laterally along it, which takes time and can bring water from some distance away. Surface runoff arrives during the storm; rock-surface flow arrives afterward. The timing is genuinely diagnostic, and it puts the effective remedy below grade rather than in the gutters.

Yes, though the discharge point is the constraint rather than the drain. On sloping ground a gravity drain to daylight is best, with no pump to fail. Where the rock leaves nowhere lower to go, an interior perimeter drain to a sump is the practical alternative. What does not work is expecting backfill in a rock excavation to drain by itself, because there is nowhere for it to drain to.