Foundation and Drainage in Puget Sound: Costs, Causes and How to Hire
Most foundation problems in the Seattle area start with water, not concrete. Drainage repairs typically cost $4,000 to $30,000, crawlspace encapsulation $8,000 to $20,000, and push or helical piers $1,800 to $3,500 each. Fixing the water first often solves what looks like a structural problem, or at least keeps a structural repair from failing.
What foundation and drainage work costs here
| Repair | Installed range | When it applies |
|---|---|---|
| Downspout extensions and regrading | $800 – $4,000 | Water pooling against the house |
| French or curtain drain | $4,000 – $18,000 | Groundwater moving toward the house |
| Footing drain replacement | $10,000 – $30,000 | Crushed or clogged original drains |
| Interior drain and sump | $6,000 – $18,000 | Basements with recurring seepage |
| Crawlspace vapor barrier | $2,500 – $6,000 | Damp crawlspace, no standing water |
| Crawlspace encapsulation | $8,000 – $20,000 | Persistent moisture, mold, humidity |
| Crack injection | $800 – $3,000 per crack | Non-moving cracks that leak |
| Piers, push or helical | $1,800 – $3,500 each, usually 6 – 20 | Settlement at the perimeter |
| Seismic bolting and bracing | $6,000 – $25,000 | Pre-1980 houses on crawlspaces |
Why water causes most problems here
Much of the region sits on glacial till: dense soil that water cannot easily soak through. Rain moves sideways along it until it meets a foundation. Add hillside lots, eight months of rain, footing drains from decades ago that have crushed or filled with roots, and downspouts that empty next to the walls, and water ends up in crawlspaces and basements. Saturated soil also loses strength under footings, which is how drainage problems turn into settlement.
Signs and what they usually mean
- Standing water or efflorescence in the crawlspace or basement: drainage.
- Musty smell and cupped floors above a crawlspace: humidity under the house.
- Hairline vertical cracks in poured concrete: usually shrinkage.
- Stair-step, diagonal or widening cracks, sticking doors, sloping floors: movement, usually needs an engineer.
- Cracks around a downhill corner: settlement where water collects.
Engineer first on structural problems
If the signs point to movement, have a licensed structural engineer diagnose it before a repair company sells a fix. An engineer is paid to find the cause; a pier company is paid to install piers. The engineer's report also becomes the document buyers, lenders and the city ask for.
Permits for foundation and drainage work
Piers, underpinning, structural repairs and seismic retrofits need building permits. Drainage work often does not, unless it connects to the city's storm system, crosses a property line or is in a critical area. Work on steep slopes may require geotechnical review. Check with the Permit Checker.
How to vet a foundation or drainage contractor
- Confirm L&I registration, bond and insurance.
- Ask whether an engineer has assessed the problem, or whether they will bring one in.
- Ask where the collected water will go and whether that discharge is allowed.
- Ask for a camera inspection of existing footing drains before replacing them.
- For piers, ask for the engineer's design: number, location and depth.
- Ask for a transferable warranty.
Foundation quote red flags
- A pier proposal with no engineer involved.
- Waterproofing paint on the inside of a basement wall sold as a cure.
- A drain that discharges onto a neighbor's property or a slope.
- High-pressure sales on the first visit.
Foundation and drainage guides by city
Questions about foundations and drainage
Is a wet crawlspace an emergency?
Not usually, but it shortens the life of posts, joists and insulation and often leads to mold. Fix it before the next wet season.
Do all cracks need repair?
No. Hairline shrinkage cracks may only need sealing. Cracks that widen, offset or come with sticking doors need assessment.
Can I sell a house with foundation repairs?
Yes. Buyers accept documented repairs with an engineer's letter and permit records far more readily than unexplained cracks.
Does encapsulation fix water problems?
No. It controls humidity. Standing water needs drainage first.
How long do repairs take?
Drainage work one to two weeks; piers several days; encapsulation two to four days.