Basement Waterproofing Cost in Seattle (2026)
Average cost in Seattle
US$1,500 — US$18,000
US$4 — US$10 per sq ft
Cost Breakdown
ItemizedProfessional waterproofing crew and excavation
45%
Membranes, sealants, gravel, and vapor barriers
30%
Sump pump units and drainage piping
15%
SDCI fees for excavation and plumbing
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 Cost
InteractiveEstimated Cost
US$7,040 — US$10,560
Based on 8 sources and market data for Seattle. Actual costs may vary depending on specific project requirements.
🏢Top Waterproofing Contractors in Seattle
Verified providersExpert Masonry and Foundation Repairs
221 1st Ave W, Seattle, WA 98119, USA
63 reviews
Embassy Masonry And Foundation Repairs
1700 7th Ave, Seattle, WA 98101, USA
61 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
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 glacial till soil and high water tables, combined with over 150 days of annual rainfall, require more robust drainage systems. This complexity typically pushes local averages to $7,350, compared to the $5,000 national average.
For projects involving excavation or structural drainage changes, the Seattle Department of Construction & Inspections (SDCI) typically requires permits ranging from $500 to $1,200 depending on the project scope.
Interior systems, which manage water after it enters, typically cost between $5,000 and $13,500. Exterior waterproofing, which requires full excavation to stop water at the source, ranges from $15,000 to over $40,000.
A professional installation for a high-capacity submersible sump pump with a battery backup typically ranges from $1,500 to $4,500, including labor and electrical upgrades.
📊Our Methodology
How we collect dataAggregated from 5+ 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: today. Updates run weekly. All costs in USD.