How Much Does a French Drain Cost? (2026 Guide)

A French drain is one of the most effective solutions for persistent basement water intrusion or yard drainage problems. The cost varies significantly based on where the drain goes, how long it needs to be, and what the ground looks like. Here’s what to expect.

French Drain Cost Overview

Exterior perimeter drain: $5,000-$15,000. This is the more expensive option because it requires excavating around the foundation, installing the drain system, and backfilling. It’s the most effective at keeping water away from the foundation before it can penetrate.

Interior perimeter drain: $3,000-$10,000. Installed inside the basement along the perimeter, below the concrete floor. Less expensive than exterior because it doesn’t require major excavation, but it manages water after it enters rather than preventing entry.

Yard drainage trench (surface French drain): $2,000-$6,000. A shallower trench drain for redirecting surface water away from the home or yard. Simpler to install than perimeter systems around foundations.

Cost Per Linear Foot

Most contractors price French drains by linear foot plus equipment and disposal:

• Interior French drain: $50-$100 per linear foot
• Exterior French drain: $75-$150 per linear foot
• Yard drainage trench: $30-$75 per linear foot

A typical 1,500 sq ft basement has roughly 150-160 linear feet of perimeter. An interior system at $75/ft comes to approximately $11,000-$12,000 before any additional equipment costs.

What’s Included

A complete French drain system typically includes:

• Excavation (exterior or interior concrete cutting)
• Perforated pipe wrapped in filter fabric
• Drainage stone (washed gravel)
• Sump pump basin and pump if not already present ($800-$1,500 additional)
• Discharge line to an appropriate outlet
• Backfill and surface restoration

Interior systems require cutting through the basement floor, which adds concrete removal and disposal costs. Exterior systems require major excavation, waterproof membrane application, and often landscaping restoration.

Factors That Drive the Price Up

Soil and rock conditions: Rocky soil or heavy clay significantly increases excavation costs. Contractors hit bedrock or massive roots unexpectedly, and the additional equipment time adds to the bill quickly.

Depth to foundation footing: Deeper foundations require deeper trenches, more pipe, and more excavation.

Access constraints: Limited access on the exterior (close to neighboring properties, landscaping features) or interior (finished basement requiring demo) increases labor costs.

Sump pump requirement: If no sump pump exists, adding one is typically required for interior systems. Budget $800-$1,500 for the basin, pump, and discharge line.

Waterproofing membrane: Exterior French drain installations are often paired with a waterproofing membrane applied to the foundation wall. This adds $2,000-$5,000 but significantly improves performance.

Interior vs. Exterior: Which Is Better?

This is the most common question homeowners have when pricing a French drain. The honest answer depends on your situation:

Choose exterior if: The water source is hydrostatic pressure from saturated soil outside, you have the budget, and the yard is accessible.

Choose interior if: The exterior is inaccessible, you’re working with a limited budget, or the water is coming through foundation cracks and floor joints (which an interior system manages effectively).

Many waterproofing specialists recommend exterior for new construction and interior for existing homes with active water problems — not because interior is inferior, but because exterior excavation on an existing home disrupts landscaping significantly.

Codes and Standards Worth Knowing

Waterproofing work tied to a permit pull defaults to the foundation drainage and dampproofing requirements in the ICC’s International Residential Code, the residential building-code framework most US municipalities adopt. If mold has developed in connection with the water intrusion, the EPA’s mold cleanup guidance sets the practical thresholds (around 10 square feet) where a homeowner should step back and bring in a remediation pro. A contractor who can reference both when scoping the work is more current than one who works off house style alone.

Frequently Asked Questions

Does a French drain solve all basement water problems? French drains address water intrusion from hydrostatic pressure and surface runoff. They don’t fix structural cracks, window well flooding, or water coming in through above-grade openings. A proper diagnosis of where your water is coming from is essential before choosing a solution.

How long does a French drain last? With proper installation and maintenance, a French drain system lasts 30-40 years. The filter fabric can clog over time in certain soil conditions. Some contractors include cleanout access ports to flush the system periodically.

Do I need a permit for a French drain? Interior French drains rarely require permits. Exterior excavation near your foundation may require a permit depending on your municipality. Drainage work that directs water to municipal storm systems almost always requires permits. Your contractor should handle this.

Will a French drain lower my home’s value? A properly documented French drain with a warranty can actually be a selling point — it demonstrates the water issue was professionally resolved. Undisclosed active water problems are far more damaging to value.

Find licensed basement waterproofing contractors in your area to assess your specific drainage situation.