How much does a French drain cost?

Exterior French drains cost $15-$30 per linear foot professionally installed ($2,250-$4,500 for a full perimeter). Interior basement French drains cost $40-$85 per linear foot ($6,000-$15,000 for a full perimeter, including sump pump). DIY yard drains cost $5-$10 per linear foot in materials. The main cost factors are length, depth, soil conditions, and whether you need an interior system with sump pump. How deep should a French drain be?

How deep should a French drain be?

Yard and landscape French drains should be 18-24 inches deep. Foundation perimeter drains need to be at footer depth, typically 6+ feet. The drain must slope at least 1 inch per 8 feet (1% grade) toward the discharge point. Deeper drains collect more groundwater but are harder to install. For most yard drainage problems, 18-24 inches is sufficient. Can I install a French drain myself?

Can I install a French drain myself?

Yes, exterior yard French drains are a manageable DIY project. You need to dig a trench, line it with filter fabric, add gravel, lay perforated pipe (holes facing DOWN), cover with more gravel, wrap the fabric over, and backfill. A 50-foot run costs $250-$500 in materials. Interior basement French drains require cutting concrete and installing a sump pump, so professional installation is strongly recommended for those. Do French drains clog?

Do French drains clog?

French drains can clog over time, but proper installation minimizes this. Use filter fabric (geotextile) to line the trench, use washed 3/4-inch crushed stone (not limestone or fine gravel), install pipe with holes facing DOWN, and use sock-wrapped pipe for extra protection. Without filter fabric, drains typically clog within 2-5 years. With proper installation, French drains last 10-30+ years before needing maintenance.

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Woodworking & Lumber

French Drain Guide: Cost, Installation, Depth & DIY Steps

Lumberama Editorial Team, Drainage & Waterproofing Specialists Jun 22, 2026 9 min read

What Is a French Drain

Definition: A trench filled with gravel and a perforated pipe that redirects surface water and groundwater away from a specific area. Named after Henry French (1859), not the country. Used for: wet basements, soggy yards, foundation waterproofing, retaining wall drainage, driveway drainage.

How it works: Water flows downhill by gravity into gravel-filled trench. Perforated pipe at bottom of trench collects water. Pipe carries water to discharge point (daylight, storm drain, dry well). Filter fabric prevents soil from clogging gravel and pipe.

Types: Exterior (around foundation perimeter). Interior (inside basement along footer). Yard/landscape (in low-lying areas). Curtain drain (intercepts water on slope). Driveway drain (across driveway at low point).

Cost

Exterior French drain: DIY: $5-$10 per linear foot (materials). Professional: $15-$30 per linear foot. Full perimeter (150 ft): $2,250-$4,500 (professional).

Interior French drain: Professional only (requires concrete cutting). $40-$85 per linear foot. Full perimeter: $6,000-$15,000. Includes sump pump: add $1,000-$3,000.

Yard/landscape drain: DIY: $5-$10 per linear foot. Professional: $10-$25 per linear foot. Typical 50-ft run: $500-$1,250 (professional).

Cost factors: Length of drain. Depth of trench. Soil type (rocky soil costs more). Access (equipment access adds cost). Discharge point (tying into storm drain costs more). Sump pump (interior drains usually need one).

Installation Specs

Trench dimensions: Width: 12-24 inches (12 minimum). Depth: 18-24 inches (yard drains). Depth: 6 feet+ (foundation perimeter drains). Slope: 1% minimum (1 inch drop per 8 feet).

Pipe: 4-inch perforated corrugated pipe (most common). 4-inch rigid PVC with drilled holes (more durable). Holes face DOWN (common mistake: holes must face down). Sock-wrapped pipe (fabric pre-wrapped to prevent clogging).

Gravel: Washed 3/4-inch crushed stone or river rock. NO limestone (calcium clogs pipe over time). 2-3 inches below pipe. Surround pipe with 2+ inches on all sides.

Filter fabric: Non-woven geotextile fabric. Line trench before adding gravel. Wrap over top of gravel before backfilling. Prevents soil migration into gravel (clogging).

Discharge: Daylight (pipe exits on downhill slope). Pop-up emitter (aesthetic option). Dry well (underground water dispersal). Storm drain (check local codes for connection).

DIY Installation

Tools needed: Shovel or trencher (rent power trencher for long runs). Level and string line. Wheelbarrow. Tape measure. Utility knife (for fabric).

Steps: Plan route from problem area to discharge point. Call 811 for utility locates. Dig trench (12-24 inches wide, 18-24 inches deep). Establish proper slope (1 inch per 8 feet minimum). Line trench with filter fabric (leave excess for wrapping). Add 2-3 inches of gravel. Lay perforated pipe (holes DOWN). Cover pipe with 4-6 inches of gravel. Wrap fabric over gravel. Backfill with topsoil (or leave gravel exposed). Connect discharge (pop-up emitter, daylight, or dry well).

Common mistakes: Insufficient slope (water pools instead of flowing). Holes facing up on pipe (collects sediment faster). No filter fabric (drain clogs within 2-5 years). Using fine gravel (clogs faster than coarse). Not calling 811 (hitting utility lines).

Interior vs Exterior

Interior French drain: Installed inside basement along foundation footer. Concrete floor cut with saw (3-4 inch channel). Drain tile placed in channel below slab level. Channel filled with gravel, new concrete poured over. Water collected, piped to sump pit, pumped out. Best for: existing homes with wet basements. Cost: $40-$85/linear foot.

Exterior French drain: Installed outside around foundation perimeter. Requires excavation to footer depth (6+ feet). Waterproofing membrane applied to foundation wall. Drain tile placed at footer level. Gravel backfill. Best for: new construction, comprehensive waterproofing. Cost: $15-$30/linear foot.

Which to choose: Interior: less disruptive, no landscaping damage, faster. Exterior: more effective long-term, protects foundation wall. Both: maximum protection (often recommended together).