Basement Finishing Cost in Seattle, WA
Based on 446 basement finishing building permits filed in Seattle between 2015 and 2026, the typical declared project value is $44,384, with most landing between $26,564 and $65,000. These are real records from Seattle's public building-permit data, declared job values, not contractor estimates or AI guesses.
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Basement Finishing values over time in Seattle
Median declared value moved from $43,128 in 2019 to $59,750 in 2024, up 39% over that span. Each year below is computed from the filings that actually cleared in Seattle.
Recent basement finishing permits in Seattle
Actual filings from Seattle's public permit records. Declared job values, not final paid prices.
| Filed | Declared value | Work described |
|---|---|---|
| 2026-06-04 | $10,000 | Construct alterations to add sleeping room in unfinished basement of one-family dwelling |
| 2026-05-13 | $89,699 | Construct alterations to lower floor and finish basement of existing single-family residen |
| 2026-03-10 | $74,335 | Construct alterations to finish basement of existing single-family dwelling per plan. |
| 2025-11-04 | $38,000 | Re-screen for STFIInterior remodel of existing SFR. Incorporate two small portions of exis |
| 2025-07-09 | $25,000 | Alterations to finish basement in a single-family residence subject to field inspection. |
| 2025-06-16 | $75,000 | Screen for STFI Hi - I would like to finish my unfinished basement and have it considered |
| 2025-06-03 | $50,000 | Construct alterations to convert portions of unfinished basement to conditioned living spa |
| 2025-05-27 | $70,000 | Construct substantial alterations to finish basement provide egress opening and revise k |
| 2025-03-08 | $60,000 | Alterations to finish the basement to a single-family residence subject to field inspecti |
| 2024-12-17 | $69,500 | Construct substantial alterations to finish basement alterations at main floor and new ba |
| 2024-11-11 | $100,000 | Construct alterations to unfinished basement and house per plans |
| 2024-10-05 | $50,000 | Construct alterations to finish basement level of one-family dwelling subject to field in |
| 2024-09-13 | $88,240 | Construct alterations to convert existing unfinished basement to conditioned/habitable liv |
| 2024-07-31 | $20,000 | Allow Attached Accessory Dwelling Unit (AADU) within existing dwelling per land use code. |
| 2024-07-08 | $44,000 | Construct interior non-structural alterations to convert unfinished basement to living sp |
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Add your price →How to read these numbers
A permit's declared value is the job cost the owner or contractor stated when they pulled the permit. It tracks the real cost of the work but can run a bit under what was actually paid, since it often leaves out some labor and finish costs. Treat the range as a grounded starting point. What basement finishing actually costs in Seattle comes down to home size, materials, and scope.
Where this comes from
Every figure is pulled from Seattle's public building-permit records and classified by the work described. Nothing is estimated or AI-generated. How the data works. The moment a Seattle homeowner adds a real receipt, this page upgrades to show what neighbors actually paid next to these permit values.
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