Seattle · King County
Grading & Drainage in Seattle, WA
Grading, French drains, retaining walls and RV and equipment pads across Seattle, from north Seattle neighborhoods. Built so water moves away from the house instead of toward it.
Why drainage matters on Seattle properties
Glacial till and outwash across most of the city, with landslide-prone slopes and soft fill in some lowlands. That is the root of most wet-yard, wet-crawlspace and failing-patio problems we see. Water that cannot soak in runs along the surface or perches on the hard layer until it finds the lowest point.
Hills and ridges between Puget Sound and Lake Washington, with steep slopes and ravines through many neighborhoods. Slopes push water downhill onto the next lot, and flat ground leaves it nowhere to go. Getting the grade right is cheaper than fixing what water does to a foundation.
Thornton Creek, Piper's Creek, the Sound and lake shorelines carry critical-area rules, and Seattle maps Environmentally Critical Areas for steep slopes and landslide-prone ground. Where drainage can legally discharge depends on these features, so we plan the outlet first and the trench second.
Common grading projects in Seattle
Wet yards and crawlspaces
Regrading and French or curtain drains for Seattle yards that stay soggy all winter because water perches on the hard till below.
Retaining walls on slopes
Block and rock retaining walls that hold back sloped Seattle yards and driveways, built with drainage behind them so they last.
Grading away from the foundation
Reshaping the ground around Seattle homes in Lake City and Wedgwood so it falls away from the house, the cheapest fix for water at the foundation.
Ditches and culverts
Cleaning and regrading drainage ditches, and setting culverts under driveways, on the low, wet ground around Seattle.
Downspout tightlines
Connecting downspouts to solid pipe that carries roof water to an approved outlet instead of dumping it next to a Seattle foundation.
What our grading work in Seattle covers
- Retaining Walls
- French Drains & Footing Drains
- Rough & Finish Grading
- RV & Equipment Pads
- Yard Drainage Correction
- Erosion Control
Permits & Rules
Grading and retaining wall permits in Seattle
Inside city limits, the Seattle Department of Construction and Inspections (SDCI) handles grading permits; outside them, the King County Department of Local Services. Small regrading and yard drains usually do not need one, but larger volumes of cut or fill, work in a critical area, or changes to how water leaves the property often do.
Retaining walls taller than about four feet, or walls holding back a driveway or slope, typically need engineering and a permit. We build to the approved plan and can tell you on the site walk when a wall is likely to need one.
Cost & Timing
What affects the cost of grading in Seattle
We do not publish flat prices because no two Seattle sites are the same. These are the things that move the number most here.
Slope and access
Steep Seattle lots take smaller machines, more careful staging and sometimes engineering, which adds time compared with flat, open ground.
Tight lots
Narrow side yards and alley access in Seattle mean compact equipment and shorter truck loads. We plan it so it costs less than it could.
Soft ground
Where Seattle soils are soft or wet, over-excavation, fabric and imported rock are often part of the job, and we price that in up front.
Buffers and permits
Work near Seattle's rivers, creeks, lakes or shoreline can need permits and limits on where machines go. That affects scope and schedule more than price.
Haul-off and disposal
How much material leaves the site, and what it is, drives cost. Our own trucks keep that predictable on Seattle jobs.
When to schedule grading in Seattle
Grading in Seattle goes best in the drier months, when soil compacts properly and trenches stay open. Wet-season work is doable with erosion control and the right material, and we plan for it in the quote.
Seattle's till soils hold water through the winter, which is when drainage problems show up. That is a good time to see where water goes, and the dry season is the time to fix it.
Where We Work
Grading and drainage across Seattle
In Seattle, DirtRaptor mostly works the north end, from Lake City and Wedgwood to Greenwood and Ballard. Seattle lots are tight, access is often by alley, and the city has detailed rules for trees and steep slopes.
We regrade yards, install French drains and curtain drains, build block and rock retaining walls, and set gravel RV and equipment pads across Lake City, Wedgwood, Maple Leaf, Northgate, Greenwood, Ballard, View Ridge and Magnolia.
Craftsman and mid-century homes on small lots, with a lot of ADU, townhome and redevelopment work. Older lots often have no real drainage at all, while newer ones sometimes have drains that were never connected. We find out which before we dig.
We also do grading nearby in Kirkland, Shoreline, Lake Forest Park and Kenmore. See everything we do in Seattle, read our full guide to grading, or browse all service areas.
Why DirtRaptor
Why Seattle owners call us for grading
Owner on the machine
On Seattle jobs you talk to the person who walks the site, writes the quote and runs the equipment.
Trees and dirt, one crew
If trees are in the way of your Seattle project, we take them down ourselves instead of waiting on a separate tree service.
Our own trucks
Haul-off and deliveries run on our schedule along I-5 and SR 99, not a subcontractor's.
Built for slopes
We plan machine placement, drainage and erosion control for Seattle's sloped ground before we start.
How a grading job runs
- 01
Site Assessment & Water Tracing
- 02
Design & Elevations
- 03
Excavation & Base Preparation
- 04
Build, Drainage & Backfill
Real Jobs
Recent DirtRaptor work near Seattle
Demolition · Edmonds, WA
Driveway Removal & Concrete Prep
Tearing out an old blacktop driveway and prepping the ground for a new concrete pour — broken material hauled off, base left clean and ready.
Demolition · Everett, WA
Condemned 100-Year-Old Shed Teardown
A 100-year-old shed, condemned and unsafe, brought down and hauled off — the site left graded flat and clean.
Questions
Grading & Drainage in Seattle: FAQs
Why does water collect around homes in Seattle?
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Glacial till and outwash across most of the city, with landslide-prone slopes and soft fill in some lowlands. When water cannot soak in, it follows the surface toward the house. Regrading so the ground falls away from the foundation, plus a drain where needed, usually solves it.
Do retaining walls need a permit in Seattle?
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Walls over about four feet, or walls supporting a driveway, building or slope, usually need engineering and a permit from the Seattle Department of Construction and Inspections (SDCI) (or the King County Department of Local Services outside city limits). Shorter landscape walls often do not. We confirm before building.
Where can drainage water go on my Seattle property?
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It has to go somewhere approved: an existing storm system, a dispersion area or an infiltration trench where the soil allows. Thornton Creek, Piper's Creek, the Sound and lake shorelines carry critical-area rules, and Seattle maps Environmentally Critical Areas for steep slopes and landslide-prone ground. We plan the outlet before we trench.
How much does grading cost in Seattle?
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It depends on the site, so we quote after a free site walk rather than guessing on the phone. The biggest drivers in Seattle are usually slope and access, tight lots, soft ground. You get a written number with inclusions and exclusions spelled out.
When is the best time to schedule grading in Seattle?
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Grading in Seattle goes best in the drier months, when soil compacts properly and trenches stay open. Wet-season work is doable with erosion control and the right material, and we plan for it in the quote.
Can you work on a tight Seattle lot with alley access?
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Yes. Compact tracked machines and our own trucks let us dig, demo and haul off from alley access, with the alley protected and kept open as much as possible.
Do you handle site prep for ADUs in Seattle?
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Yes. ADU site prep usually includes small demolition, tree work, excavation for the foundation and utility trenching. We do it all with one crew.
Do I need a permit for a retaining wall in Washington?
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Generally yes above four feet, measured from the bottom of the footing rather than finished grade — which catches people out. Engineered drawings are typically required at that point too. Lower walls near property lines, slopes or critical areas can also require review.
Ready for a real number in Seattle?
Send the address and a few photos. We walk the site for free and come back with a written quote.
