Basement Waterproofing Cost in Seattle (2026)
Average cost in Seattle
$2,350 – $18,500
$3 – $15 per sq ft
In Seattle, the average is $7,280 and most projects cost between $2,350 and $18,500, or about $3 – $15 per sq ft. Prices are before tax and based on 7 sources.
Cost Breakdown
ItemizedSkilled trade labor and installation
40%
Sealants, membranes, and drainage pipes
25%
Trenching and heavy machinery rental
15%
SDCI fees and structural assessment
10%
Combined Seattle/WA rate of 10.35%
10%
Sales Tax at 6.5%
📋What's Included
ScopeTypically Includes
- Interior drain tile system
- Sump pump installation
- Vapor barrier
- Crack injection sealing
- Labor
Typically Excludes
- Exterior excavation waterproofing
- Foundation repair
- Mold remediation
- Dehumidifier
- Landscaping restoration
Based on interior waterproofing for a standard 800-1,000 sq ft basement.
🧮Estimate your project
LiveYour estimate in Seattle
Likely range $3,276 – $16,016
- Labor40%$2,912
- Materials25%$1,820
- Excavation & Equipment15%$1,092
- Permits & Engineering10%$728
- Sales Tax10%$728
Interior sealant
$7,280
Interior drainage / weeping tile
$11,648
Exterior excavation
$17,472
Calibrated to 7 researched sources for Seattle. Before tax. Real quotes vary with site conditions.
📈Price Momentum
Year-over-year~1 year ago
$6,967
Today
$7,280
Basement Waterproofing in Seattle is ↑ 4.5% compared to roughly a year ago — about $313 more on the average project.
Comparison derived from the year-over-year change rate, not a month-by-month price index. We don't store historical snapshots yet — when we do, this will become a real time series.
🏢Top Waterproofing Contractors in Seattle
Verified providersCity Construction Solution
1997 Bellevue Way SE, Bellevue, WA 98004, USA
206 reviews
Seattle Elite masonry and foundation repair
221 1st Ave W #200, Seattle, WA 98119, USA
40 reviews
KG Basement Waterproofing Seattle
800 S Weller St, Seattle, WA 98104, USA
34 reviews
Embassy Masonry And Foundation Repairs
1700 7th Ave, Seattle, WA 98101, USA
62 reviews
Provider data sourced from public business directories. Ratings and reviews are public and may change. LookupCost is not affiliated with listed providers.
💬What People Actually Paid
Community❓Common Questions
Seattle's unique geological characteristics, including heavy clay soils and high water tables, combined with over 150 days of annual rainfall, require more robust drainage solutions. Additionally, local labor rates are significantly higher, with total compensation for trade labor rising approximately 4.6% to 5.8% annually.
For projects involving excavation or structural changes, the Seattle Department of Construction & Inspections (SDCI) typically charges between $500 and $1,200 in permit fees, depending on the project's complexity and the inclusion of plumbing or drainage work.
Interior systems, which manage water after it enters, typically range from $3,000 to $13,500. Exterior solutions, which prevent water entry through excavation and membranes, are significantly more expensive, often starting at $15,000 and exceeding $40,000 for complex residential properties.
Yes, professional waterproofing in the Pacific Northwest typically yields a 60% to 80% return on investment (ROI). Given Seattle's wet climate, a dry, certified basement is a critical selling point that prevents structural devaluation from mold or foundation rot.
📊Our Methodology
How we collect dataAggregated from 7+ verified web sources and cost databases
Licensed contractor estimates and regional cost guides
Government construction and labor statistics
Community-reported project costs and reviews
Last data collection: 1 months ago. Updates run weekly. All costs in USD.
About this data
Cost figures are estimates synthesized from public market data using AI research and refreshed regularly. Real project costs vary by scope, materials, contractor, and site conditions. Always get verified quotes from licensed contractors for your specific project.
Spotted bad data? Let us know — we'll review and update.