Across 919 permits filed since 2025-03-08, the median is $30,000; half of projects fall between $7,000 and $210,000. 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 Connecticut actually reported when they pulled permits.
Recent filings
- 21’1”x 19’1” multi-story home addition, 4’x 15’10” front porch extension, 16’x10’ laundry garage bay. A multi-story residential addition consisting of a new full foundation/basement expansion, an additional garage bay, a expanded front pTown of Southington · 2026-09-04$180,000
- NEW 2 STORY S/F RESIDENCE W/6 BR'S, PARTIALLY FINISHED BASEMENT AND UNFINISHED ATTICWestport · 2026-09-04$1,384,000
- Partial finishing of basement, half bath, baseboard heatTown of Westbrook · 2026-09-03$22,000
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 Connecticut came in between $7,000 and $210,000. 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 New YorkBasement finishing on Long Island