French Drain Installation Cost in 2026: What to Expect

Interior French drains typically cost $40-$75 per linear foot because they require cutting through a concrete basement floor, excavating underneath, and patching the concrete afterward. Exterior French drains run $25-$50 per linear foot and involve trenching along the foundation, which requires heavy equipment and landscaping restoration. Interior drains are more common for existing homes because exterior excavation is more disruptive.

A short 30-foot drain along one wall might cost $1,200-$2,500. A full perimeter drain (100-150 linear feet for an average basement) runs $4,000-$10,000. Exterior drains around the full foundation perimeter of a 1,500 sq ft home can push $6,000-$12,000 when you factor in equipment, excavation depth, and landscape repair.

Exterior French drains need to be deep enough to intercept groundwater before it reaches the foundation. Typical depth is 18-24 inches for yard drainage but 4-6 feet for foundation drainage. Every additional foot of depth increases labor and equipment costs significantly. Rocky soil or high water tables add further complications.

Interior French drains need somewhere to send the collected water. If you already have a sump pump and pit, connection costs $200-$400. If you need a new sump pit and pump, add $600-$1,500 to the project. Most interior French drain installations include sump pump setup since the drain is useless without a way to remove the collected water.

Clay soil is harder to excavate and drains poorly, which may require wider trenches and more gravel. Rocky soil requires specialized equipment. Tight access around the home's exterior can prevent heavy equipment from reaching work areas, forcing more hand digging. Interior drains in basements with finished floors require demolition and restoration of flooring.

“Do you recommend an interior or exterior French drain for my situation, and why?”

Why this matters: The right approach depends on where water is entering. A contractor who evaluates your specific water intrusion pattern before recommending a solution is more trustworthy than one who defaults to the same approach for every home.

“What pipe material will you use, and what's the expected lifespan?”

Why this matters: Corrugated pipe is cheaper but clogs more easily and lasts 10-15 years. Rigid PVC costs more but lasts 50+ years. Knowing what you're getting helps you assess the true long-term value.

“How will you ensure proper slope throughout the drain run?”

Why this matters: The drain must slope at least 1% toward the collection point. A professional should use a laser level to verify grade. Improper slope is the number one reason French drains fail.

“Is a sump pump included, and what happens to the collected water?”

Why this matters: Water needs somewhere to go. If the drain can't gravity-flow to daylight, you need a sump pump. Make sure the quote addresses the full water removal path, not just the drain pipe.

“What warranty do you offer, and does it cover drain failure?”

Why this matters: A quality French drain should last 15-30 years. Look for at least a 5-year warranty on workmanship. Some waterproofing companies offer transferable lifetime warranties, which adds real value at resale.

“Do I need permits for this work, and who handles that?”

Why this matters: Many municipalities require permits for drainage work, especially if it connects to storm sewers or affects neighboring properties. The contractor should handle permits and ensure the installation meets local codes.

“Will this solve my water problem completely, or is additional waterproofing needed?”

Why this matters: French drains address water at the floor level, but wall seepage may require additional waterproofing treatments. An honest contractor will tell you upfront if the drain alone won't fully solve your issue.