French Drain Installation in Portland, Wilsonville & Lake Oswego

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At Foundations First Northwest, we install French drains for homes across the Portland metro area. These drainage systems protect your foundation by directing water away from your property. We handle installations in crawl spaces, basements, and exterior locations.

What Is a French Drain?

A French drain is a perforated pipe system surrounded by gravel. Water seeps into the pipe through small holes and flows away from your home. This reduces hydrostatic pressure around your foundation and prevents water damage.

The system works through simple gravity. You dig a trench with a slight slope, place the pipe, and backfill with clean rock. Water naturally moves from high points to low points where it exits through a discharge system.

Crawl Space Drainage Systems

Crawl space French drains prevent standing water under your home. We start by finding the highest and lowest points in your crawl space. The drain runs from high to low with at least a 1% slope—about one inch of drop per 10 feet.

We dig a four-inch trench and set perforated socked pipe along the path. Clean river rock goes in first as a base layer, then we backfill over the pipe. This keeps water flowing and your crawl space dry.

Basement Perimeter Drains

Basement installations require more work but solve serious water problems. We break out a 10-inch section of your concrete slab along the foundation wall. The trench goes 4-6 inches below the footing.

After digging, we add a gravel base and install the drainage pipe with the same 1% slope. We place drainage mat four inches up the stem wall and lay plastic over the rock. Then we pour new concrete to match your existing floor.

This interior drainage system catches water before it enters your basement. The water flows to a sump pump or discharge point.

Exterior French Drains

Outside installations work best for yard drainage and foundation protection. Before digging, we locate all utility lines. Safety comes first.

The exterior trench runs 12-18 inches deep and nine inches wide. We install either a catch basin or pop-up discharge at the end point. After drilling drainage holes in the basin, we set the pipe and connect everything.

For perforated socked pipe, you don’t need landscape fabric. For triple wall pipe, we install fabric first to prevent clogs. Then we backfill with clean river rock.

Water is your foundation’s biggest enemy. When soil gets saturated, it expands and pushes against your foundation walls. During dry periods, soil contracts and pulls away. This constant movement causes cracks and structural damage.

A French drain intercepts water before it reaches your foundation. The system reduces groundwater pressure and keeps your basement or crawl space dry. This protects your home’s structural integrity and prevents costly repairs down the road.