Across 455 permits filed since 2025-03-09, the median is $13,000; half of projects fall between $4,500 and $47,386. Figures are permit valuations reported to building departments. National cost guides answer this question with averages from other markets; these numbers are what homeowners in Westchester County, NY actually reported when they pulled permits.
Recent filings
- Finished basementVillage of Dobbs Ferry · 2026-09-05$3,150
- Plumbing for the legalization of the basement and interior alterations to create an accessory dwelling unit consisting of 5 fixtures including an ejector pump.Village of Ardsley · 2026-09-04$7,000
- File to Legalize Basement storage rooms, Boiler room & basement BathroomCity of Yonkers · 2026-09-01$2,000
How to read these numbers
Permit valuations are the project cost the applicant reports to the building department. They skew slightly low — nobody rounds up for the permit fee — and scope varies, so the middle-half range is the honest picture: half of all basement finishing permits in Westchester County, NY came in between $4,500 and $47,386. We exclude permits under $1,000, jobs filed as whole-house construction, and counties whose building departments don't reliably report valuations.
Same project, other places
Basement finishing in New YorkBasement finishing in ConnecticutBasement finishing on Long Island