Storm & Flood Damage Recovery in Philadelphia, PA

That is normal in a rowhouse and it complicates the repair more than the drying. Roof planes and party walls run continuous across several houses, so water entering at one address travels along the framing and appears wherever the first opening is. Drying has to cover the wet assembly, which may sit on both sides of a wall you do not own. Getting access early, before either owner starts closing things up, is the part that most often goes wrong.

Intensity rather than total. The combined sewer here handles steady rain well; what overwhelms it is the rate of an August cell dropping an inch or more in under an hour across blocks with almost no absorbent ground. The line surcharges and relieves through the lowest openings connected to it. A March rain of the same total, spread over a day, never reaches that rate and the system keeps up.

If the cellar has ever backed up through a drain or a fixture, yes. A backwater valve on the building sewer closes when the public line surcharges, which is precisely the failure mode here. It needs to be accessible for inspection and it needs to be maintained, because a valve that has silted open provides nothing. It is one of the few one-time investments in this stock that reliably changes the outcome.