Waterproofing · Service

French drain installation — but which one?

Three completely different products are sold under this one name, and they differ in price by an order of magnitude. Work out which one you are being quoted before you compare a single number.

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In short

What is french drain installation?

A French drain is a trench holding perforated pipe surrounded by washed stone and wrapped in filter fabric, sloped so water collects into the pipe and runs somewhere useful. The problem is that the name gets applied to at least three unrelated installations: a shallow yard drain that clears standing surface water from a low spot, a curtain or interception drain dug deeper across a slope to cut off subsurface water heading toward the house, and an interior perimeter drain installed inside the basement under the edge of the slab. Before you compare quotes, establish which of the three each contractor means — because they solve different problems and the prices are not remotely comparable.

Triggers

Signs you need french drain installation

A section of lawn stays soggy for days after rain and the grass there has thinned out or died
Water sheets down a slope and arrives at the back of the house every storm
A patio, driveway or walkway sends its runoff toward the foundation instead of away
Landscaping beds against the house stay saturated even when the rest of the yard has dried
Water is showing up in the basement or crawl space on the uphill side of the house specifically
A retaining wall is weeping, bulging or has efflorescence across its face
The ground beside the foundation has settled into a trough that now holds water against the wall
You have already extended the downspouts and the wet spot is still there

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The job

How french drain installation actually works

Establish which drain is actually being proposed

Ask for the trench depth, the length, where it starts, where it discharges, and whether it is intercepting surface water or subsurface flow. Those five answers identify the product regardless of what it is called on the quote.

Watch for: A quote that says only "French drain — 60 linear feet". That describes a trench, not a solution, and it makes two bids impossible to compare.
Rule out the cheaper fixes first

Downspouts discharging at the wall, overflowing or undersized gutters, and a grade that has settled toward the house cause a large share of the water that gets blamed on a missing drain. Extending downspouts and re-establishing slope costs a fraction of a trench.

Watch for: A contractor who quotes a drain without walking the roof drainage with you. If they have not looked up, they have not diagnosed anything.
Find where the water is going and confirm there is somewhere to send it

Every drain needs an outlet lower than its inlet — daylight on a slope, a dry well, or a permitted storm connection. Fall is set with a laser or a level over the full run, not eyeballed.

Watch for: No identified outlet, an outlet on a neighbour's property, or a flat lot where the fall is claimed rather than measured. A drain with nowhere to go relocates your puddle instead of removing it.
Excavate to the depth the job actually requires

A surface yard drain can be shallow. A curtain drain has to reach below the level the subsurface water is travelling at, often down toward the base of the layer that is carrying it, or it simply passes underneath.

Watch for: A curtain drain dug to convenient shovel depth on a slope. Too shallow is the single most common reason this type fails, and it fails while looking perfectly built.
Bed the pipe in washed stone and wrap it in filter fabric

Clean, angular washed stone gives water room to move. Non-woven filter fabric lining the trench keeps soil fines out of that stone. Together they are what stops the drain silting shut over a few seasons.

Watch for: Sock-wrapped pipe used instead of a fabric-lined trench in silty or clay soil. The sock clogs against the pipe and the drain dies quietly. Also watch for unwashed crusher run backfilled straight against the pipe.
Orient and connect the pipe correctly

Perforations, solid runs, cleanouts and any tie-in of downspouts or surface grates get planned as one system. Cleanouts at the ends and at direction changes are what make the drain maintainable in ten years.

Watch for: No cleanouts anywhere. A buried drain with no access cannot be jetted or inspected, so its first blockage is also its last.
Backfill and restore the surface honestly

Stone to near the surface with fabric folded over the top keeps the drain permeable; capping it with topsoil and sod makes a tidier lawn but slows how quickly surface water reaches the stone. That is a design trade-off you should be asked about.

Watch for: A drain capped with heavy soil and sod when it was sold as a surface-water fix. It will look finished and drain far more slowly than promised.

Money

What does french drain installation cost?

Prices are usually quoted per linear foot and swing enormously with depth, soil, access and what is on top — a shallow lawn run is a different order of expense from a deep curtain drain cut through a slope with machinery. Get depth and outlet stated before comparing rates.

See the full french drain installation cost guide — by material, size and region →

Straight answer

When french drain installation is the wrong call

Everyone else ranking for this is paid when you say yes. Here's when you shouldn't.

Your downspouts still empty next to the house. Nothing on this page is a better first move than moving roof water away from the foundation. Do it, watch it through a wet season, and see how much of the problem is left.
There is nowhere lower to send the water. On a flat lot with no daylight outlet, a gravity drain either does nothing or becomes an underground pond. That situation needs a pumped or infiltration design, priced honestly, not a standard trench.
You are being sold an exterior yard drain to fix an interior basement leak. These are sometimes related and often not. If water is entering the basement, the diagnosis has to come first — a lawn drain thirty feet away may not touch it.
The wet area is caused by a downspout, an irrigation leak or a neighbour's runoff. Each has a targeted fix. A trench is an expensive way to manage water that should not be arriving in the first place.
The trench would run through mature tree roots you want to keep. Cutting a drain line through a root plate can cost you the tree years later. Reroute the drain or accept the risk deliberately.
Nobody will commit to the outlet in writing. The outlet is the whole job. If the quote is vague about where the water ends up, you are buying a trench and inheriting the problem it was meant to solve.

Your options

Types of french drain installation

French drain vs sump-only approaches

When intercepting water outside beats collecting it inside.

Drain tile, stone and fabric

The components, and which combinations actually stay open.

Standing water near the foundation

Symptom-side diagnosis before you commit to a trench.

Compare waterproofing options side by side →

Straight answer

Can I do this myself?

Call for utility locates before any digging, every time, including on your own property. Gas, electric, water, sewer and communications lines are routinely shallower than people expect, and a locate is free where a strike is not.

Reasonable to DIY

Extending downspouts well away from the foundation with rigid pipe or roll-out extensions
Cleaning gutters and confirming they are not overflowing at the corners during a real storm
Building up soil to re-establish a slope away from the house where it has settled
Digging out and rebuilding a short, shallow surface drain in a flat, cable-free part of the yard
Adding a surface grate over an obvious low spot and connecting it to an existing outlet

Call a licensed pro

Any trench that needs a surveyed or instrument-set fall over a long run — guessing the slope is how these fail
A curtain or interception drain on a slope, where the required depth is a judgement call, not a standard
Anything within digging distance of a foundation, a retaining wall, or a septic field
Work where the outlet is not obvious and a dry well, pump or permitted connection may be needed
Any drain intended to fix water that is already entering the basement — that is a diagnosis question, not a trenching one

Before you sign

What to check when hiring for french drain installation

Is this a surface drain, a curtain drain, or an interior system?

The question that makes competing quotes comparable. Contractors bidding different products against each other is the normal state of this market.
How deep is the trench, and how did you decide that depth?

Depth is what separates a drain that intercepts subsurface water from one that lets it pass underneath. A confident answer with a reason behind it is a good sign.
Where does it discharge, and have you confirmed the fall?

You want a physical location you can walk to and a measured drop, not an assurance. This is where gravity drains fail on flat lots.
What stone and what fabric, and is the trench lined or the pipe sleeved?

In silty and clay soils a fabric-lined trench with washed stone lasts; a sock on the pipe surrounded by fines does not. It is the difference between a decade and a couple of seasons.
Where are the cleanouts?

A drain you cannot inspect or jet is a drain you will eventually re-dig. Cleanouts are cheap at installation and impossible to add later.
Who calls in the utility locates, and who is liable for a strike?

Should be the contractor, in writing. Get it settled before a machine is on your property.
What did you rule out before recommending this?

A drainage contractor who tells you the gutters and grading were checked first has earned more credibility than one who arrived with a price.

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Local pros

French Drain Installation near you

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Related work

Often done at the same time

Interior Drain Tile

The interior perimeter version

Sump Pump System

When gravity has nowhere to go

Exterior Waterproofing

When the wall itself needs treating

Basement Waterproofing

The overall decision

All waterproofing services →

FAQ

French Drain Installation — questions people ask

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What is the difference between a French drain and a curtain drain?

A curtain drain is a French drain positioned and dug specifically to intercept water moving through the soil from uphill before it reaches a structure. It sits across the slope, above the thing being protected, and it has to be deep enough to catch the layer the water is travelling in. A general yard French drain is usually shallower and aimed at surface water pooling in a low spot. Same construction, different depth, different placement, different problem.

Does a French drain need an outlet, or can it just soak away?

It needs somewhere for the water to go. On a sloping lot that is usually daylight. On a flat lot it may be a dry well sized for the volume, or a pumped basin. What does not work is a level trench full of stone with no exit — it fills, stays full, and stops accepting water exactly when you need it most.

How long does a French drain last?

It depends almost entirely on whether soil fines can reach the stone. A fabric-lined trench with washed stone in reasonable soil can work for a very long time; the same drain built with unwashed aggregate or a sock-wrapped pipe in silt can silt up within a few seasons. Cleanouts and the ability to jet the line are what keep it recoverable either way.

Will a French drain fix my wet basement?

Sometimes, and only if the water reaching your basement is coming from a source the drain actually intercepts. Exterior drains address water moving toward the house. They do not address a high water table pushing up under the slab, a crack in the wall, or roof water landing at the foundation. Get the source identified before you commit, because the wrong drain in the right-looking place changes nothing.

Can I install a French drain myself?

A short, shallow surface drain in an open, utility-free part of the yard is genuinely within reach for a determined homeowner. What is not is any run where the fall has to be instrument-set over distance, anything near the foundation, and any curtain drain where depth is a judgement call. And regardless of scale, call for utility locates first — that part is not optional.