Storm & Flood Damage Recovery in Tacoma, WA

That is the classic local mechanism and it is a soil boundary rather than a spring. Permeable glacial outwash sits over dense till in much of this area; rain soaks down through the outwash, hits the till, and then travels sideways until it daylights, often part way down a slope. A house built at that contact gets water arriving through the uphill wall. Interception with a curtain drain uphill of the foundation is the standard answer.

Because the rain is persistent rather than intense. A month of steady November rain keeps everything saturated continuously, so an assembly never dries between events. Small failures that would be self-correcting in a drier climate simply run all winter. That is also why the damage is often discovered late, as staining or a smell, rather than as a dramatic event on a particular night.

More than in most climates, and for a specific reason. Heavy conifer litter blocks gutters and downspouts through the autumn, precisely when the rain becomes continuous. A blocked downspout concentrates the entire roof area onto one spot of foundation soil for weeks at a time. Clearing gutters in late October is one of the few genuinely high-value maintenance tasks against water damage in this area.