Paver PatioView full sizeCharcoal grid with planted joints
Large charcoal units set with open joints for grass, so the surface drains through itself rather than off itself. It photographs best wet, which in Seattle is most of the year.
Drainage · Seattle
French Drains & Yard Drainage in Seattle
Standing water in a Seattle garden is almost never a mystery, and it is almost never a lawn problem. The city sits on glacial till — a dense hardpan under a foot or two of topsoil — and takes 38 inches of rain a year with nearly all of it between October and March. Water goes down until it hits the till, then stops. Once the topsoil above is saturated there is nowhere for the next inch to go, so it sits on the surface. Nothing about that improves with reseeding, aeration or a load of topsoil, all of which we regularly find have already been tried by the time we are called. It improves when the water is given a route out of the property.
- Typical range
- $10–$25 per linear foot
- From our base
- Base of operations — Capitol Hill
- Ground here
- Predominantly glacial till (Alderwood series) — a dense hardpan under 12–24 inches of topsoil that water sits on rather than passes through.
Covered outdoor lounge with a fire table beside an artificial turf lawn on a Seattle property
What we get called about
Drainage problems specific to Seattle.
Seattle takes 38+ inches of rain a year and almost all of it arrives October to March. That single fact decides more landscaping outcomes here than plant choice ever does — a patio without a drainage plan is a patio that heaves, and a lawn on undisturbed till is a lawn that sits under water all winter.
- A lawn that is spongy from November to March on ground that was fine in August
- Water pooling against a foundation or finding its way into a crawlspace
- Moss winning against grass that never gets a chance to dry out
- A downspout discharging into a border and undermining a wall or patio
- Runoff from a neighbouring property higher up arriving on your ground
Worth knowing in Seattle
Book the assessment in the wet months, not in July. Between October and March we can see exactly where water collects, which way it runs and how long it takes to clear. A dry August site visit gives you a drain designed from your description of last winter rather than from the evidence.
Why a soakaway does not work here
The most common bad proposal we are asked to price against is a soakaway pit — a hole filled with rock that the drain runs into, on the theory that the water will disperse into the surrounding ground.
On glacial till it will not. The entire reason the garden floods is that the ground beneath it does not absorb water at any useful rate. Digging a hole, filling it with rock and piping water into it does not create absorption; it creates a buried reservoir that fills up and then backs up. In a normal Seattle winter it stays full for months.
A drain needs somewhere legal and physical to discharge to. On a sloped Seattle lot that is usually daylight — a point lower than the drain where water can run out freely — and where it is not, it is an approved connection. Establishing which one you have is the first thing we do, because a drainage system with no viable outfall is money spent on a trench.
The method
How we build drainage, wherever the job is.
The sequence does not change between neighbourhoods — what changes is the ground it is applied to. Full detail on the drainage service page.
- 01
Find out where the water actually comes from
Roof, surface runoff, a neighbouring property's grade, or groundwater sitting on the till. These need different answers and guessing wastes the whole job.
- 02
Establish where it can discharge to
A drain needs somewhere legal and physical to go — daylight at a lower point, or an approved connection. A drain that terminates in a hole is a soakaway on ground that does not soak.
- 03
Cut the trench to a consistent fall
Continuous fall along the whole run. A trench that dips holds water and silts up, which is the most common reason a retrofit drain stops working.
- 04
Lay pipe, rock and geotextile
Perforated pipe bedded in clean washed rock, wrapped in geotextile so the surrounding soil cannot migrate in and clog the void.
- 05
Reinstate the surface
Turf, planting or hard surface put back so the finished job does not read as a scar across the garden.
What it costs in Seattle
$10–$25 per linear foot
Seattle drainage runs $10 to $25 per linear foot, with most residential projects landing between $1,000 and $4,000. The same hundred-foot job gets quoted anywhere from $5,000 to $14,000 across this market, which is why we itemise what is actually being installed — pipe, rock, geotextile, and the discharge — rather than handing over a single number.
No down payment
You pay after the project is fully completed.
Fixed price, agreed up front
The estimate you sign is the price you pay.
0% interest for up to 6 months
Spread the cost with no interest.
Warranty on hardscaping
Covers hardscape work; vegetation excluded.
Local questions
Drainage in Seattle, answered.
General questions about this service are on the service page. These are the ones that only come up here.
Will a French drain fix water in my Seattle crawlspace?
Often it is a large part of the answer, and sometimes it is not the answer at all — it depends where the water is entering. Exterior drainage that intercepts surface and shallow groundwater before it reaches the foundation, combined with regrading so the ground falls away from the building and downspouts discharging well clear of it, resolves a lot of crawlspace water in this city. What exterior work will not fix is water coming through a failed foundation or a hydrostatic problem below the drain line. That is a different trade, and we will say so rather than sell you a drain that does not address it.
Do I need a drain, or would regrading be enough?
Regrading is frequently enough and it is usually cheaper, so it is worth asking before committing to a system. If the problem is a single low area, or water sitting against the house because the ground falls the wrong way, reshaping the ground to move water away solves it without a pipe. If the problem is that the whole garden saturates and stays saturated, regrading only moves the puddle. The other cheap fix people miss is roof water: a downspout discharging into a border delivers an enormous volume to one spot, and tying it into a proper run sometimes fixes what looked like it needed a full system.
How long does a French drain last in Seattle conditions?
A properly built one should run for decades with essentially no attention. The failures we get called to fix are almost all construction faults rather than age. No geotextile, so soil migrated into the rock over a few seasons and silted up the void that was carrying the water. An inconsistent fall with dips along the run that hold water and collect fines. Or perforated pipe surrounded by sandy fill instead of clean washed rock, which has no void to speak of from day one. If there are catch basins in the system they want the leaf litter clearing once a year, which takes minutes.
Can drainage be done at the same time as a patio or wall?
It should be, and it is significantly cheaper that way. The machine is already on site, the ground is already open, and the drainage can be designed into the levels rather than retrofitted around them. Doing it afterwards means excavating through work that has just been finished and paid for. On most of our Seattle hardscape projects the drainage is not a line item people opt into — it is simply part of building something that will still be flat and standing in ten years.
Serving Seattle and surrounding neighbourhoods
Base of operations — Capitol Hill.
Capitol Hill · Ballard · Queen Anne · Magnolia · West Seattle · Green Lake · Wedgwood · Madison Park · Laurelhurst · Mount Baker · Seward Park · Fremont · Wallingford · Columbia City
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Recent work
Built in Seattle.
Paver PatioView full size
Outdoor LivingView full sizeCovered lounge, fire table & turf lawn
A modern pergola over a paved lounge, edged straight into a turf lawn that stays green all winter, with a plank path running the length of the lot.
2 photos
Retaining WallsView full sizeLit seat wall, steps and turf lawn
Lighting recessed into the wall face and the step risers, so the garden still works through eight months of dark Seattle evenings. Photographed the night it was commissioned.
2 photos
FlagstoneView full sizeFlagstone patio with a fire bowl
Hand-fitted flagstone laid tight, with a fire bowl and seating where the lawn used to sit wet.
Book a free drainage assessment in Seattle.
We come out, look at the ground, and put a fixed written price together. No deposit, and it does not change once agreed.
Free estimate
Drainage in Seattle — get a price.
Three minutes on the form. We reply during office hours, Monday – Friday, 9:00 AM – 7:00 PM, and we come out and look at the site before quoting anything.
Or call (425) 533-9734
Request received
Thank you — we have your details. We reply during office hours, Monday – Friday, 9:00 AM – 7:00 PM. If it is urgent, call (425) 533-9734.