Across 51 permits filed since 2025-05-02, the median is $12,000; half of projects fall between $4,150 and $29,850. 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 London County, CT actually reported when they pulled permits.
Recent filings
- Spicer will run approximately 15 feet of one half inch copper gas line from existing propane tank on site LSF house at rear. Line will go from tank into unfinished basement through the sill plate and run along overhead over to and into a 26Montville · 2026-10-30$1,057
- Insulate & Finish Basement WallsGroton · 2026-10-23$3,000
- Wiring for basement renovation in new indoor mini golf areaMontville · 2026-10-14$5,000
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 London County, CT came in between $4,150 and $29,850. 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