Foundation Drainage in Hillsboro, Oregon: Keeping Water Out

Protecting a Hillsboro Foundation From Water

Hillsboro homes face one of the tougher foundation-water situations in the Portland metro. The city sits on the flat Tualatin Valley floor, where heavy clay holds water against the structure, the water table rises high through winter, and the level ground gives water nowhere to drain. Through months of steady Pacific Northwest rain, the soil around a Hillsboro foundation stays saturated, building hydrostatic pressure that pushes moisture into any below-grade space it can reach.

Foundation drainage is the system that intercepts water before it reaches your structure and carries it to a safe outlet. When it fails or was never installed, you get a wet basement, a damp crawlspace, mold, and over time structural damage. This guide explains how foundation water threatens Hillsboro homes and how to keep it out.

For the broader picture, see our guide to property and site drainage in Oregon. For statewide pricing, see foundation drain installation cost in Oregon.

How Water Reaches a Hillsboro Foundation

Saturated Clay Against the Walls

Hillsboro's clay holds water rather than draining it, so through the wet season the soil against your foundation stays fully saturated. That standing water creates hydrostatic pressure that forces moisture through cracks, joints, and porous concrete.

A High Water Table

The Tualatin Valley's groundwater rises close to the surface in winter. When the water table sits near or above the base of a foundation, water is pressing against the structure from below as well as the sides.

Flat Ground With No Drainage Path

On level valley lots, water that reaches the foundation has no natural slope to carry it away. It collects and lingers exactly where it does the most harm.

Downspouts Discharging at the Footing

Roof runoff dumped right next to the foundation is one of the most common and most fixable causes of foundation moisture in Hillsboro, adding concentrated water to an already saturated zone.

How Foundation Drainage Is Done in Hillsboro

The right system depends on the home, the soil, and the water table, so an assessment comes first. Common solutions include:

• Footing (foundation) drains — A perforated pipe in a gravel bed at the base of the footing collects water and carries it to a safe outlet. This is the core defense against saturated clay and a high water table.
• Exterior regrading — Reshaping the soil to slope away from the foundation removes the most common cause of foundation moisture, often at modest cost.
• Interior drainage systems — Where a high water table makes exterior excavation impractical, an interior perimeter drain to a sump can be the better route.
• Downspout extensions and drainage — Carrying roof water well away from the footing protects the foundation and reduces the load on every other system.
• Daylight or sump outlets — Because flat ground and clay limit gravity drainage, the outlet may be a daylight point where slope allows or a sump-and-pump system where it does not.

Our excavation services cover the careful foundation excavation these jobs require.

What Foundation Drainage Costs in Hillsboro

Foundation drainage is priced by scope — exterior regrading is far cheaper than excavating a full perimeter footing drain. Industry baseline ranges commonly referenced include:

Work	Industry Baseline Range
Exterior footing drain (per linear foot)	$20–$80
Full perimeter foundation drain	$5,000–$15,000+
Interior perimeter drain with sump	$3,000–$12,000+
Exterior regrading	$1,000–$4,000

In Hillsboro, cost drivers are excavation depth, the high water table (which can require dewatering or push the job toward an interior system), the perimeter length, and the outlet. A regrade-and-downspout fix sits at the low end; a full perimeter drain or an interior system with a sump runs well above it. Foundation work is high-stakes, so a professional assessment is essential. See foundation drain installation cost in Oregon for the broader breakdown.

Why This Is Not a DIY Job in Hillsboro

Excavating against a foundation is unforgiving, and Hillsboro adds a high water table and flat ground to the equation. Dig too aggressively next to a footing and you can undermine it; hit groundwater and the trench fills as you work; choose a poor outlet on flat ground and the water has nowhere to go. A contractor who works Washington County evaluates the grade, the clay, the water table, and how water is reaching the structure, then designs a system — exterior, interior, or both — that actually carries water away.

Get Your Hillsboro Foundation Drainage Quote

Cojo Excavation & Asphalt protects Hillsboro and Washington County homes from foundation water, with solutions designed for Tualatin Valley clay and a high winter water table. We assess how water is reaching your foundation and recommend the most effective, cost-appropriate fix.

Request a free drainage assessment and we will respond within 24 hours. Learn more about our excavation services for Hillsboro-area homes.