Across 35 permits filed since 2025-03-09, the median is $15,000; half of projects fall between $4,000 and $88,800. 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 Middlesex County, CT actually reported when they pulled permits.
Recent filings
- Construction of 22' x 22' addition to garage with 2nd floor addtion on existing garage 20' x 30'Haddam · 2026-08-27$88,800
- Construction of new addition 22' x 22' to garage with 2nd floor on existing part of garage 20' x 30'Haddam · 2026-08-25$88,800
- New plumbing of new in law apartment additionHigganum · 2026-08-17$1,000
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 home addition permits in Middlesex County, CT came in between $4,000 and $88,800. 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
Home addition in New YorkHome addition in ConnecticutHome addition on Long Island