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.
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.
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
Seeing something not on this list? Browse waterproofing problems by symptom →
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 forA 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 forA 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 forNo 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 forA 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 forSock-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 forNo 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 forA 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.
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 →
If the number is the problem, here are the ways people pay for it →
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When french drain installation is the wrong call
When saying yes is the wrong move:
- 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.
Types of french drain installation
| Option | What it means for you |
|---|---|
| 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. |
Can I do this myself?
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
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.
French Drain Installation near you
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Sources
Sources last checked
- Basement Waterproofing basicsU.S. Environmental Protection Agency (moisture)Retrieved 2026-08-04Moisture control principles that drive waterproofing scopes.
- Occupational Employment and Wages — Construction TradesU.S. Bureau of Labor StatisticsRetrieved 2026-08-04Labor cost context for home-services trades nationally.
Sources for figures and claims on this page.
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