Basement Finishing Cost in Seattle (2026)
Average cost in Seattle
US$40,000 — US$400,000
US$250 — US$600 per sq ft
Cost Breakdown
ItemizedSkilled trades and general contracting
40%
Framing, drywall, flooring, and finishes
35%
SDCI fees and architectural drawings
10%
Moisture control and foundation prep
10%
Unexpected repairs and mold remediation
5%
Sales Tax at 6.5%
📋What's Included
ScopeTypically Includes
- Framing & drywall
- Basic flooring (LVP or carpet)
- Electrical (outlets & lighting)
- Egress window (if required)
- Painting
- Basic bathroom rough-in
Typically Excludes
- Full basement bathroom
- Built-in bar or kitchen
- Home theater wiring
- Waterproofing (separate cost)
- Permits & inspections
Assumes an unfinished basement with existing concrete floor and basic utilities.
🧮Estimate Your Cost
InteractiveEstimated Cost
US$30,120 — US$45,180
Based on 9 sources and market data for Seattle. Actual costs may vary depending on specific project requirements.
📈Price Momentum
Year-over-year~1 year ago
US$133,568
Today
US$142,250
Basement Finishing in Seattle is ↑ 6.5% compared to roughly a year ago — about US$8,682 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 Basement Finish Contractors in Seattle
Verified providersFuller Living Construction
5304 Green Lake Way N, Seattle, WA 98103, USA
53 reviews
Levite Construction CO
5608 17th Ave NW Suite 1490, Seattle, WA 98107, USA
40 reviews
Contemporary Home Construction, Llc
11335 NE 122nd Way, Kirkland, WA 98034, USA
79 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
Yes. Seattle Department of Construction and Inspections (SDCI) requires permits for any project involving structural changes, egress windows, or new electrical/plumbing. Permit fees typically range from $1,200 to $5,000 depending on project value.
Homeowners can expect a return on investment (ROI) of 60% to 80%. In Seattle's high-density market, adding livable square footage or an ADU significantly boosts resale value.
Adding a full bathroom typically adds $40,000 to $75,000 to the total project cost, largely due to the need to break concrete slabs for new plumbing lines.
Costs are 20-50% higher due to Seattle's high labor rates (averaging $150/hr for some trades), strict energy codes, and the critical need for advanced waterproofing in the Pacific Northwest climate.
📊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: 2 days 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.