Planning ranges for every drainage job, what pushes them up or down, and how to tell a fair quote from an inflated one — written for homeowners staring at a wet basement.
| Job | Typical range* | When it applies |
|---|---|---|
| Downspout tie-in / redirect | $300 – $2,000 | Roof water dumping at the foundation — cheapest high-impact fix |
| Yard French drain | $2,500 – $8,000 | Standing water, soggy lawn, a wet low spot |
| Exterior footing drain | $6,000 – $15,000+ | Failed clay tile; water at the foundation, yard accessible |
| Interior perimeter drain + sump | $6,000 – $15,000 | Wet finished basement — the standard Seattle fix |
| Sump pump (install / replace) | $1,200 – $4,000 | New basin + pump; battery backup adds ~$600–1,500 |
| Curtain / interception drain | $4,000 – $12,000 | Hillside lot, water arriving from uphill |
| Full basement waterproofing system | $10,000 – $20,000+ | Perimeter drain, sump, backup, wall treatment together |
*Planning ranges from regional drainage-industry norms — not a quote. Seattle jobs vary with length, depth, access, exit point, and what an assessment finds. Every real number starts with someone looking at your property.
The single biggest driver. A lot that falls away to a daylight exit is the cheap case — gravity does the work. A flat lot with no downhill needs a sump, and a storm-system tie-in (where the city allows it) adds permit and connection cost. Same drain, very different price, decided by grade.
Drainage is priced heavily per foot, and depth compounds it. A footing drain around a full foundation on a deep Seattle basement is a different project than a 30-foot yard drain.
A run under open lawn is cheap to reach and restore. The same run under a driveway, a patio, mature landscaping, or a retaining wall costs more to excavate and much more to put back. Interior systems avoid this — one reason they're often chosen for finished Seattle basements over exterior digs.
Seattle's narrow lots, alley-only access, and steep driveways can force hand-digging where a machine can't reach — slower and costlier. It's a real factor here that flatter, more open markets don't face.
Failed clay tile, roots, and buried surprises add time. Homes from the pre-1980 stock often hide an abandoned drain or an unexpected footing depth that the assessment catches and the quote should account for.