Across 1,055 permits filed since 2025-04-27, the median is $18,000; half of projects fall between $5,000 and $70,000. 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 New York actually reported when they pulled permits.
Recent filings
- The construction of a 34.5 x 32.83 (oa) (1,133 sf) second floor addition, interior alterations to existing first floor, an 18 x 15 (oa) (270 sf) one (1) story rear addition with basement, one (1) 6 ft wide sliding glass door, one (1) 9 ft wVillage of Mineola · 2026-10-26$383,811
- ONE FAMILY RESIDENCE WITH UNFINISHED BASEMENTTown of Warwick · 2026-10-23$458,000
- FINISHED BASEMENT TO INCLUDE A CRAFT ROOM, FULL BATHROOM, KITCHEN AND MEDIA ROOM. EXTEND EXISTING DECK APPROXIMATELY 14' X 12'Town of Warwick · 2026-10-23$50,000
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 New York came in between $5,000 and $70,000. 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 ConnecticutBasement finishing on Long Island