French Drain Installation Cost Calculator

Length is the primary cost driver - most contractors price french drains by the linear foot. A shallow surface drain in soft soil runs $10-$20 per foot. A deep perimeter drain (24-36 inches) in firm soil runs $25-$50 per foot. Systems that require 4+ feet of excavation due to footing depth or clay layers can reach $75-$100 per linear foot once equipment costs are factored in.

Sandy loam is a contractor's dream - easy digging, good drainage. Heavy clay soil is the opposite: it's slow to excavate, prone to caving, and may require specialized backfill material to ensure adequate water movement around the pipe. Rocky soil or sites with poor machine access (tight side yards, steep slopes) also add significant labor. Expect a 30-50% premium over base pricing in difficult soil or access conditions.

The cheapest discharge option is daylighting - running the pipe to a low point in the yard or property edge where water flows out freely. That can cost little or nothing beyond the pipe run itself. A dry well (an underground gravel-filled pit that disperses water into the soil) adds $500-$1,500. Tying into a municipal storm drain or sump pump system is the most expensive option at $1,500-$3,000 due to permitting and tie-in requirements.

Running a french drain under an existing concrete patio, driveway, or paver walkway requires saw-cutting, demolition, and reinstallation after the drain is set. This can easily double the cost of the affected section. Concrete removal and repour runs $6-$12 per square foot on top of drain costs. Paver removal and relay is $8-$20 per square foot. Plan for this upfront - it's one of the most common sources of change orders.

Simple residential drainage systems typically don't need an engineer. But if the drain is meant to protect a foundation, handle significant water volume, or tie into a public storm system, many municipalities require a stamped engineering plan before issuing a permit. Civil engineering fees for a residential drainage plan run $700-$2,000 depending on complexity. Some drainage contractors offer design-build services that include basic design at a lower cost than a separate engineer.