Homeowners think about gutters. Fewer think about the complete path water takes from roof to somewhere harmless, and that path is where things go wrong.
The volume involved
A roof is a large collection surface, and Western Washington rainfall is persistent rather than dramatic. That combination means substantial volumes arriving at the same handful of discharge points, month after month, through the wet season.
Concentrating that at the base of a wall is what produces saturated ground, wet crawl spaces and foundation problems. It is not a dramatic failure — it is the same modest error repeating for years.
Watch it happen
The single most useful thing you can do is go outside during heavy rain and watch.
Is water overflowing anywhere along the gutter run? Is it sheeting over the front edge rather than running to the downspouts? Where does each downspout actually discharge, and where does that water then go? Is anything pooling against the house?
Ten minutes in the rain tells you more than any amount of inspection in dry weather, because in July everything looks fine.
Where downspouts should discharge
Well away from the foundation. How far depends on your ground and slope, but the base of the wall is never the right answer.
Options run from simple extensions and splash blocks through to buried drainage lines carrying water to a proper discharge point. Extensions are cheap and effective and frequently missing entirely.
Watch what happens after the water lands. An extension that discharges onto ground sloping back toward the house has achieved nothing.
Grading
The ground should slope away from the house. This is frequently wrong in older properties, because soil settles over decades and landscaping gets added without regard to it.
Check by looking, and confirm during rain by seeing which way water runs. Regrading is not glamorous work and it is often the most effective drainage improvement available.
The Thurston County note
Olympia and the southern Sound receive more annual rainfall than Seattle, on flatter ground with slower-draining soils. Gutter and drainage capacity adequate elsewhere can be marginal there, and drainage work is routine rather than exceptional.
Where drainage has a ceiling
Worth being honest about. In the Skagit valley floor and parts of Thurston County, high water tables mean groundwater arrives from below regardless of how well surface water is managed.
Drainage improvements help but cannot overcome that, and a contractor promising they will fully solve a crawl space problem in those locations may be overpromising. Encapsulation with active humidity control is often the realistic answer there.
Buried lines need maintenance too
Underground drainage lines block, and because they are buried nobody notices until water backs up at the downspout or surfaces somewhere unexpected.
If your property has buried drainage, know where it discharges and check that the outlet is clear and flowing. An outlet buried under years of soil and vegetation is a common and invisible failure.
What good looks like
Gutters clear and correctly fallen. Downspouts discharging well clear of the foundation. Ground sloping away from the house. Water reaching a point where it can soak away or run off without returning. Nothing pooling against the wall during or after rain.
None of it is complicated. It just requires looking at the whole path rather than the first few feet of it.