French drain cost

A French drain costs $10 to $90 per linear foot installed depending on depth and placement. A 50 foot shallow yard drain is $500 to $1,750. An interior basement drain is $40 to $85 per foot. A deep exterior perimeter drain at footing level is $30 to $90.

The name covers three quite different installations, and the price difference between them is entirely how deep somebody has to dig.

What each type costs

Type	Per linear foot	What it does
Yard or curtain drain	$10 to $35	Intercepts surface and shallow groundwater
Interior basement drain	$40 to $85	Collects water at the wall and floor joint, to a sump
Exterior perimeter drain at footing	$30 to $90	Relieves pressure before water reaches the wall
Driveway or trench drain	$30 to $80	Catches surface runoff at a hard surface

A typical residential job:

Job	Length	Typical total
Wet patch in the lawn	30 to 50 ft	$600 to $1,800
Curtain drain across a slope	60 to 100 ft	$1,200 to $3,500
Interior basement perimeter	60 to 100 ft	$3,000 to $8,500
Full exterior perimeter, excavated	100 to 150 ft	$6,000 to $15,000

Interior and exterior drains usually come with a sump pump at $650 to $2,500, and a battery backup is $350 to $1,800 more.

A drain pipe discharging water onto open ground — Slope and an outlet decide whether a drain works, and both are invisible once the trench is filled. Ask where the water leaves, then go and look at it.

How it works, and the two things that decide whether it does

A French drain is a trench with a perforated pipe in the bottom, surrounded by washed stone, wrapped in filter fabric, sloped so water runs somewhere.

Slope. The pipe needs a consistent fall, about an inch every ten feet. A drain laid flat holds water instead of moving it, and a drain that sags in the middle collects silt at the low point until it blocks. This is the most common installation failure and it is invisible once the trench is filled.

Somewhere to go. Water has to exit: daylight on a slope, a dry well, a storm drain if the municipality allows it, or a sump pump. A drain with no outlet is a buried trench full of water. Ask where the water leaves, and go and look at that point.

Filter fabric matters too. Washed stone against bare soil silts up within a few years; wrapped in fabric it stays porous for decades.

Which drain for which problem

A soggy patch in the lawn after rain. Shallow yard drain, the cheapest option.

Water running down a slope toward the house. Curtain drain across the slope above the house, intercepting it before it arrives. Often the highest-value drain you can install.

Water at the basement wall and floor joint after heavy rain. Hydrostatic pressure. Interior perimeter drain to a sump, or exterior work if the wall itself is the problem.

A driveway or patio that sheds water at the garage door. Trench drain across the opening.

Damp walls with no visible entry point. Probably condensation rather than groundwater. A dehumidifier costs a fraction of a drain, so diagnose before digging.

Do the free things first

Before paying for a drain, check the water is not being delivered to the house by its own roof.

Downspouts. Should discharge at least six feet from the foundation, ten is better. Extensions cost $10 each. A single downspout dumping at the wall puts thousands of gallons a year exactly where you least want them.

Gutters. Blocked ones overflow at the wall.

Grading. The ground should fall away from the house six inches over the first ten feet. Mulch beds built up against the foundation year after year reverse it.

A surprising number of French drain quotes are for problems that a $40 downspout extension and an afternoon of shovel work would solve. A contractor who checks these before quoting is one worth using.

Doing it yourself

A shallow yard drain is a realistic DIY project and saves 50% to 70%. It is a trench, a pipe, stone and fabric. The tools are a shovel or a rented trencher, and a laser or line level to confirm the fall.

The rules that matter: maintain the slope the whole way, use washed stone rather than anything with fines in it, wrap the stone in fabric, lay the pipe with its holes down rather than up, and confirm the outlet before you start digging.

Call 811 before you dig. It is free, and utilities mark their buried lines within a few days.

Interior basement drains and exterior footing drains are not DIY. One means breaking out and replacing the slab; the other means excavating against the foundation.

Frequently asked questions

How long does a French drain last?

Thirty to fifty years when built with washed stone and filter fabric. Without fabric, ten to fifteen before silt clogs it. Rigid perforated pipe outlasts corrugated flexible pipe by a wide margin and costs a little more.

Does it need maintenance?

Very little. Keep the outlet clear and check it after heavy rain. Interior systems depend on the sump pump, which needs testing twice a year and replacing every seven to ten.

Can it be installed under a lawn without wrecking it?

The trench is 12 to 24 inches wide and the grass over it will take a season to recover. Some contractors lift and relay turf, which costs a little more and looks far better.

Will it fix my wet basement?

If the water is groundwater arriving under pressure, yes. If it is condensation, a plumbing leak, or surface water entering through a window well, no. Identify the source first: this is the difference between a $6,000 fix and a $6,000 disappointment.

Interior or exterior?

Interior is roughly half the price, needs no excavation, and works in winter. Exterior stops the water before it reaches the wall and is the permanent answer. For most houses interior is the practical choice; exterior is right when the wall itself is deteriorating or the basement is finished living space.