Crawl space encapsulation cost in Seattle (2026):
prices by size and what's included
HOW MUCH DOES CRAWL SPACE ENCAPSULATION COST?
Angi puts crawl space encapsulation at $5,000 to $15,000 for most homes, with an average of $5,500, or about $2 to $4 per square foot for basic work and $3 to $10 for more extensive work. For Seattle, HomeAdvisor reports $2,276 to $5,694 (average $3,965) for the wider category of crawl space and basement waterproofing and encapsulation.
Crawl space encapsulation cost
| Source | Reported cost |
|---|---|
| Angi, most homes (national) | $5,000–$15,000 |
| Angi, average (national) | $5,500 |
| Angi, full range | $1,500–$20,000 |
| HomeAdvisor, Seattle (waterproofing and encapsulation category) | $2,276–$5,694, average $3,965 |
Cost by crawl space size
| Crawl space | Reported cost | With 10.55% sales tax |
|---|---|---|
| 1,000 sq ft | $5,000–$7,000 | $5,528–$7,739 |
| 2,000 sq ft | $8,000–$12,000 | $8,844–$13,266 |
| 4,000 sq ft | $15,000–$20,000 | $16,583–$22,110 |
What's included, and what each part costs
| Part | Reported cost |
|---|---|
| Vapor barrier | $0.50–$0.70 per sq ft |
| Dehumidifier | $800–$1,200 |
| Sump pump | $60–$170 (pedestal), $100–$400 (submersible) |
| Spray foam insulation | $0.50–$1.50 per sq ft |
| Dealing with mold first | $1,000–$3,500 |
Not sure whether you have a moisture or mold problem? A test is cheaper than a full job: see radon and mold testing cost. Water in a finished basement is a different job: see basement waterproofing cost in Seattle.
Drains and permits in Seattle
- Drains outside the house need a permit. SDCI Tip 503 treats footing and foundation drains as service drains, and says a side sewer permit is needed before work on side sewers and service drains.
- Inside the footprint, pipes count as plumbing under Tip 503.
- Ask who will pull any permit, and whether the quote includes it.
Before you sign
- Get the crawl space size and every part (barrier, dehumidifier, sump, insulation) itemized in writing.
- Ask what happens to existing mold or standing water before the barrier goes down.
- Check the contractor on L&I's Verify a Contractor tool, and keep the first payment small: see contractor down payments.
Frequently asked questions
How much does crawl space encapsulation cost?
Angi puts most jobs at $5,000 to $15,000, with an average of $5,500, or about $2 to $4 per square foot for basic work. For Seattle, HomeAdvisor reports $2,276 to $5,694 for the wider waterproofing and encapsulation category.
How much does it cost to encapsulate a 1,000 sq ft crawl space?
Angi lists $5,000 to $7,000 for a 1,000 sq ft crawl space. In Seattle, 10.55% sales tax brings that to about $5,528 to $7,739.
How much does a crawl space dehumidifier cost?
Angi lists $800 to $1,200 for a crawl space dehumidifier.
Do I need a permit to encapsulate a crawl space in Seattle?
Drainage work outside the house can. SDCI Tip 503 treats footing and foundation drains as service drains that need a side sewer permit before work starts. Ask SDCI about your specific project.
Does mold have to be removed before encapsulation?
Angi lists $1,000 to $3,500 to deal with mold issues and says more than minimal mold calls for remediation. Ask the contractor how they will handle it before the barrier goes in.
About these prices. The ranges are published estimates from the sources below, as of the dates shown. Material costs, labor rates, tariffs and inflation can change prices after those dates, and your home may differ. Use them to plan a budget, then get written quotes from licensed contractors.
Sources
- Angi — Crawl space encapsulation cost (data July 15, 2024)
- HomeAdvisor / Angi — Waterproofing and encapsulation companies in Seattle, WA
- SDCI Tip 503 — Side sewer permits
- Washington Department of Revenue — Custom construction
All sources accessed November 10, 2026, except SDCI Tip 503 (checked November 1, 2026).
This guide summarizes published cost estimates and City of Seattle information. Confirm permit requirements with SDCI before work starts, and get written quotes from licensed, bonded contractors. See our disclosure and disclaimer.