What's the cost of installing a French drain beside my Vancouver deck?

French drain installation alongside a deck in Metro Vancouver typically costs $15-$35 per linear foot, or $1,500-$3,500 for a standard 100-foot run. The wide price range depends on excavation depth, pipe diameter, gravel type, and whether you're dealing with clay-heavy soil common in Surrey, Richmond, and Delta.

French drains are particularly valuable for deck longevity in Metro Vancouver's wet climate. With over 1,200mm of annual rainfall and persistent humidity, proper drainage around your deck prevents the standing water and saturated soil conditions that accelerate wood rot, foundation settling, and moisture problems under the deck structure. Many deck failures in the Lower Mainland stem from poor drainage rather than structural issues.

Excavation and materials make up the bulk of French drain costs. The trench typically needs to be 12-18 inches wide and 18-24 inches deep, sloped at 1% grade (1 inch drop per 100 feet) toward the drainage outlet. In Metro Vancouver's clay-heavy soils, particularly in Richmond, Surrey, and Delta, excavation is more challenging and time-consuming than in sandy or loamy soils. The drain system includes a 4-inch perforated pipe surrounded by clean gravel (typically 3/4-inch crushed rock), wrapped in landscape fabric to prevent soil infiltration.

Professional installation versus DIY is worth considering carefully. While French drain installation might seem straightforward, proper grading, pipe placement, and connection to municipal storm systems or appropriate discharge points require experience. Many Metro Vancouver properties have complex drainage patterns due to slope, and connecting to existing storm drains may require municipal permits. Clay soil excavation is also physically demanding and may require mechanical equipment.

Additional costs can include connecting to the municipal storm system ($200-$500 for permits and inspection), adding catch basins or cleanouts ($150-$300 each), and landscaping restoration over the drain route ($5-$15 per square foot). If your deck sits on a slope—common in North Vancouver, West Vancouver, Burnaby, and Coquitlam—the French drain may need to be deeper or longer to effectively capture and redirect water flow.

For drainage issues around decks specifically, Vancouver Deck Contractors can match you with contractors experienced in both deck construction and site drainage. However, for standalone French drain installation, you'll want a drainage specialist or landscaping contractor from the Vancouver Construction Network who understands Metro Vancouver's soil conditions and municipal drainage requirements.