French Drain Cost Per Linear Foot: 2026 Price Guide

A French drain typically costs between $20 and $60 per linear foot installed. Exterior systems usually fall at the lower end of that range, while interior systems that require cutting through a concrete slab run higher. Total project cost depends on trench depth, pipe material, access conditions, and whether a sump pump is included.

What a French Drain Is and What It Does

A French drain is a trench filled with gravel or rock that contains a perforated pipe. The pipe collects groundwater and redirects it away from the foundation, usually to a storm drain, dry well, or sump pump. The purpose is hydrostatic pressure management: by giving water an easier path than through foundation walls or under a slab, the drain reduces the force pushing against below-grade concrete.

French drains are not structural repairs. They do not lift a settled slab or stabilize a bowing wall. If a foundation has active settlement or wall movement beyond the typical 2-inch limit, drainage work should be paired with structural measures such as piers or wall anchors, not treated as a substitute.

Cost Per Linear Foot by System Type

Cost estimates below are installed prices, including materials and labor, for a standard residential job. They are labeled as estimates because actual quotes vary by region, contractor, and site conditions.

For a 100-linear-foot exterior drain at $30 per linear foot:

100 ft × $30/ft = $3,000

For the same length indoors at $60 per linear foot:

100 ft × $60/ft = $6,000

These figures exclude permits, which vary by city and county and typically require 1-3 weeks for approval where applicable.

What Drives the Price

Several variables move the per-linear-foot cost within the ranges above.

Depth and excavation. A trench dug to 2 feet costs less than one dug to 6 or 8 feet because deeper digging requires more soil removal, possible shoring, and greater care around existing footings. Exterior drains installed alongside a basement foundation often reach the footing level, which can add significant labor compared with a shallow curtain drain in a yard.

Pipe material. Perforated PVC pipe is common and inexpensive. Corrugated flexible pipe costs less upfront but can crush under backfill if not protected. Some installations use PVC with filter fabric and washed stone, which raises material cost but improves long-term flow.

Access and obstructions. Exterior work near decks, patios, mature trees, or utility lines costs more because the crew must work around or remove obstacles. Interior work requires saw-cutting the slab, removing concrete, and patching afterward, all of which add labor hours.

Sump pump and discharge. If gravity discharge is not possible, a sump pump and basin are required. A residential sump pump installation typically adds $800 to $2,500 to the project, depending on pump horsepower and basin material. That fixed cost is spread across the linear footage, so shorter drains see a higher effective cost per foot.

Backfill and restoration. Replacing excavated soil, compacting it in lifts, and restoring landscaping or concrete adds to the total. Some quotes include restoration; others bill it separately.

Interior vs. Exterior: When Each Applies

An exterior French drain is installed outside the foundation wall, usually at footing depth. It intercepts water before it reaches the structure. This is the preferred approach when the yard slopes away from the house and there is room to excavate without disturbing hardscaping.

An interior French drain is installed inside the basement or crawl space, along the perimeter of the slab. It captures water that has already entered or is likely to enter through the wall-floor joint. Interior systems are common when exterior access is blocked by a tight lot, an attached structure, or finished landscaping. Because the slab must be opened and the drain tied to a sump, interior systems cost more per linear foot.

Neither system repairs a cracked or settled foundation on its own. If the foundation shows movement, a structural assessment should come first. An engineer inspection typically costs $400 to $1,500 and takes 1-2 weeks to schedule. Related repair options are priced separately; for example, pier installation ranges from $6,000 to $30,000 per job, while slab lifting runs $3 to $12 per square foot.

Sample Project Arithmetic

Consider a home with 120 linear feet of foundation perimeter needing an exterior French drain at $25 per linear foot, plus a sump pump.

Drainage pipe and labor:

120 ft × $25/ft = $3,000

Sump pump and basin:

$1,500 (mid-range estimate)

Total before permits and restoration:

$3,000 + $1,500 = $4,500

If the same job were done indoors at $60 per linear foot:

120 ft × $60/ft = $7,200

Plus sump pump:

$7,200 + $1,500 = $8,700

These are estimates. A contractor should measure the actual linear footage, trench depth, and discharge route before issuing a fixed price.

How to Get an Accurate Quote

Measure first, price second. A reliable quote should include:

• Total linear feet of drain
• Trench depth and width
• Pipe diameter and material
• Gravel volume and filter fabric
• Sump pump requirements, if any
• Permit fees, where required
• Surface restoration scope

Request an itemized quote rather than a single per-linear-foot figure. That makes it easier to compare bids and identify what is included. If foundation cracks or movement are present, schedule the engineer inspection before drainage work so the scope addresses both water management and structural needs.

Learn more about overall foundation repair pricing

See pier-and-beam foundation repair cost details

Review foundation crack repair cost guidelines