Structural Drying & Dehumidification in Shelton, CT

It is common wherever the excavation went into ledge. Blasting or cutting a basement into rock creates a hole with impermeable sides and bottom, and the backfill placed against the wall is more permeable than the rock around it. Water that gets into that backfill cannot drain down, so it fills the space and stands against the wall. A footing drain that actually discharges somewhere is essential in this condition, and many older houses do not have one.

Two reasons combine. The autumn peak here is driven partly by tropical remnants that still carry substantial moisture this far north, so single-event totals are larger. And by October the soil is no longer being dried by growing vegetation and warm sun, so it holds what it receives. Same rainfall, much less capacity to absorb it, which is why the seasonal pattern of basement problems follows the calendar as much as the storms.

Yes, from the inside or the outside, and which one makes sense depends on the site. An exterior drain addresses the water before it reaches the wall but requires excavating around the foundation, which on a ledge lot can be difficult and expensive. An interior perimeter drain and sump is less disruptive and relieves the water once it has arrived. On tight urban and valley lots the interior approach is more often the practical one.