How Much Does Foundation Drainage Cost?

What Does Foundation Drainage Cost?

Foundation drainage costs between $3,000 and $18,000, averaging around $9,000 for a comprehensive system. The range is wide because the solutions are so different: a partial interior drain is a modest job, while a full exterior perimeter system with excavation is a major one. What you pay depends on whether the drainage is interior or exterior, how many linear feet it covers, and whether excavation is involved.

Interior French Drain: $6,000 to $15,000

An interior French drain is perimeter drain tile installed at the inside base of the basement walls, routing collected water to a sump pump. It is the most common residential foundation drainage solution. The contractor breaks the concrete floor along the perimeter, excavates a trench at footing level, installs perforated pipe in gravel, and patches the concrete. The pipe feeds a new or existing sump pit. A typical full-perimeter installation in a standard basement runs $6,000 to $15,000, or $60 to $120 per linear foot. A partial installation covering one or two walls runs $3,000 to $6,000. Because nothing outside is excavated, it is much less disruptive than exterior work, and it gives any water that reaches the foundation a defined route out rather than letting it spread across the floor. (For more on this, see Interior vs. Exterior French Drain: Which Do You Need?.)

Exterior French Drain: $30 to $90 Per Linear Foot

An exterior French drain is a perforated pipe in gravel, installed in a trench outside the foundation, parallel to the wall and sloped to a discharge point or a dry well. It intercepts groundwater before it reaches the foundation wall. Cost runs $30 to $90 per linear foot including excavation, pipe, gravel, and backfill, so a 100-linear-foot drain around the home’s perimeter comes to $3,000 to $9,000. The trench is dug down alongside the foundation, ideally to the level of the footing so water is caught before it can rise against the wall. Small sections can be dug by hand; a full perimeter takes a trencher or an excavator. Expect the work to disrupt landscaping and to require care around underground utilities.

Full Drainage System: $6,000 to $18,000

A comprehensive system combines perimeter interior drain tile, a sump pump with battery backup, corrected downspout routing, and grading corrections. The total runs $6,000 to $18,000, with the perimeter drain the largest single line at $6,000 to $15,000 for a home that gets all four elements. The layers attack water at different stages: downspout tie-ins capture roof water before it ever hits the ground near the house, regrading sheds surface water away from the foundation, and the perimeter drain catches whatever still reaches the wall. Integrating surface drainage, underground drainage, and interior water management is the most reliable way to keep a basement dry over the long term. (For more on this, see What Makes Foundation Drainage Cost More (or Less)?.)

Foundation Drainage Cost at a Glance

Supporting Work That Changes the Total

Not every wet basement needs a drain tile system. The surface fixes are cheaper, and they are often the most cost-effective drainage improvement, so try them first.

Keeping the System Working

Exterior French drains can clog with sediment over 10 to 20 years as fine soil particles infiltrate the gravel and the pipe perforations. The warning signs are wet soil returning next to the foundation after a dry stretch, or water reappearing in a basement that had stayed dry. Flushing the pipe with a high-pressure water nozzle from the outlet end back through the line clears most sediment; a severely clogged drain has to be excavated and replaced. Filter fabric wrapped around the pipe and gravel at the time of installation significantly delays clogging, which makes it worth confirming in the quote.

Where the water goes matters as much as how it is collected. A drain that daylights at a lower elevation on the property is the simplest discharge. Where there is no low point and the water cannot be piped to a street or storm drain, a dry well collects the flow and lets it percolate into the surrounding soil — an option only where soil is permeable enough to accept the volume.

What Else Moves the Number

Beyond the type of drainage, the price tracks the linear footage of the perimeter, the depth of excavation, soil and site conditions, whether landscaping and hardscape must be restored, and how much grading and downspout work is folded into the scope. Rocky soil and buried obstacles add cost. Depth is a quiet but significant driver: reaching the footing on an exterior drain can mean digging down several feet along the whole wall, so two homes with the same perimeter length can price very differently depending on how deep the foundation runs. (For more on this, see The Best Foundation Drainage Solution for Your Situation.)

Because the exterior drain is priced by the foot, the interior drain sits in a set range, and a full system bundles grading and downspout work on top, the single biggest question is which of these the water problem actually calls for. That takes an on-site look at where water enters and how the lot sheds it, not an estimate made sight unseen.

Getting an Accurate Quote

Treat the ranges above as planning benchmarks, not fixed prices. Get at least two written quotes on an equivalent, defined scope before committing. Wide variation between bids usually reflects differences in material quality, scope completeness, or contractor overhead rather than simple price competition, so ask each bidder what the per-linear-foot rate includes and excludes, whether permits, cleanup, and disposal are covered, and what the labor warranty is. For any project over $500, get the scope in writing: materials, labor, timeline, inclusions, and warranty terms. Tie payments to milestones — a deposit at signing, a payment at project start, and the balance after a completion walkthrough. A contractor who wants the full amount upfront is a red flag.