Basement Finishing Cost in Seattle (2026)
Average cost in Seattle
US$30,000 — US$350,000
US$50 — US$250 per sq ft
Cost Breakdown
ItemizedSkilled trades and general construction
40%
Drywall, flooring, insulation, and fixtures
25%
Mechanical, electrical, and below-grade plumbing
15%
Moisture control, French drains, and egress
12%
SDCI fees and architectural drawings
8%
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$114,986
Today
US$121,425
Basement Finishing in Seattle is ↑ 5.6% compared to roughly a year ago — about US$6,439 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
54 reviews
Contemporary Home Construction, Llc
11335 NE 122nd Way, Kirkland, WA 98034, USA
75 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
In 2026, costs typically range from $50 per sq ft for basic finishes to $250 per sq ft for high-end remodels or ADU conversions.
Permit and design fees generally range from $5,000 to $10,000+. Seattle SDCI fees for construction permits increased by 18% year-over-year in 2026.
Yes, an egress window is required for any legal basement bedroom. Installation, including the window and well, typically costs between $3,000 and $6,500 per unit.
A full basement-to-ADU conversion typically costs between $150,000 and $350,000, driven by requirements for separate utility connections and ceiling height adjustments.
📊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 weeks 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.