Excavation
Foundation Drainage in Sherwood, Oregon: Keeping Water Out
Cojo
May 30, 2026
7 min read
Sherwood's newer subdivisions, built on the graded hills south of Tualatin, put many homes on cut-and-fill lots where water management is part of the design but not always enough for the realities of the Pacific Northwest wet season. On these sloped lots, water flows downhill toward foundations, sometimes carrying runoff from neighboring properties above. Add western Washington County's heavy clay soil and the long wet season, and Sherwood foundations face sustained moisture pressure every winter.
Foundation drainage is the system that intercepts groundwater and surface flow and keeps it away from your basement or crawlspace walls. When it works, your home stays dry through the wettest Washington County winter. When it fails, you get a musty crawlspace, efflorescence on the walls, mold, and eventually cracking as saturated clay expands and contracts against the concrete. On Sherwood's hillside lots, intercepting slope water before it reaches the foundation is often the central task.
Because every property drains differently, an effective solution starts with an on-site assessment.
Keeping water away from a foundation takes several components working together.
A footing drain is a perforated pipe set in gravel at the base of the foundation footing. It collects rising groundwater and carries it by gravity to a daylight outlet or sump. On Sherwood's sloped lots a gravity outfall is frequently available. In clay soil, the gravel envelope and filter fabric are essential to keep the pipe from clogging.
On hillside lots, an uphill curtain drain intercepts water flowing toward the house from above before it ever reaches the foundation. This is one of the most valuable tools for sloped Sherwood properties, especially where runoff arrives from neighboring lots.
Most foundation water problems begin at the surface. The standard target is a fall of about six inches over the first ten feet away from the foundation. On graded lots, settling or fill can leave the grade pitched toward the house, so regrading is often the most cost-effective single fix.
A single downspout can dump hundreds of gallons at the foundation during a downpour. Extending downspouts well away from the house, or onto a solid drain line that daylights downhill, removes a large volume before it reaches the footing.
Western Washington County around Sherwood receives well over 40 inches of rain a year, concentrated in the cool months when the ground stays saturated for weeks. The clay soils drain slowly, hold water near the surface, and expand when wet, putting lateral pressure on foundation walls. The result is sustained hydrostatic pressure through the winter.
Sherwood's graded, hilly subdivisions add slope runoff to the equation. Cut-and-fill lots can channel water toward homes, and a property below a neighbor may receive that runoff. This shapes the right solution: a footing drain with a gravity outfall is often achievable, and an uphill curtain drain frequently does the heavy lifting by intercepting slope water before it reaches the foundation. Our foundation drain installation cost in Oregon guide breaks down what these systems involve.
Any one of these warrants a closer look. Several together usually mean water is already reaching the foundation, and delay only raises the eventual repair cost.
Foundation drainage projects vary widely because every lot is different. Industry baseline ranges for exterior footing drain installation generally run from roughly $15 to $35 per linear foot for accessible work, though excavation depth, soil conditions, equipment access, and outfall distance can push real costs well above that. A full perimeter system on an existing home typically lands in the low-to-mid thousands and climbs with complexity, and adding a curtain drain for hillside interception increases scope.
Sherwood's clay soil and graded terrain can make excavation and routing more involved. Published ranges are a starting reference, not a quote. The only way to know your number is a site assessment.
Sherwood homes sit at various points on graded slopes, and a lot at the base of a hill has very different needs than one at the top. An on-site evaluation lets us check the existing grade, identify hillside water flowing toward the house including runoff from neighboring lots, find a workable outfall, and decide whether your situation calls for a footing drain, a curtain drain, a regrade, or a combination.
Foundation work done on a guess wastes money and often fails. A contractor who walks your property, checks the slope, and evaluates the soil delivers a far more accurate plan than any cost chart, and catches the slope-runoff issues common on Sherwood's subdivision lots.
If water is finding your foundation, the problem compounds with every wet season. Cojo Excavation & Asphalt provides free, no-obligation drainage assessments for Sherwood homeowners and property managers. We evaluate your grade, soil, and outfall options, then deliver a clear plan and transparent quote.
Start with the big picture in our guide to property and site drainage in Oregon, then learn more about our excavation services and how we protect Washington County homes from groundwater.
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