Across 947 permits filed since 2025-04-25, the median is $20,000; half of projects fall between $5,850 and $129,000. 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
- addition in back 12'6X42'6 add second story to the house and garage 30'X36'Town of Southington · 2026-10-23$342,000
- Provide electrical wiring, install receptacles, switches and lights in the addition Your application for a Building Permit has been reviewed for compliance with the 2022 State of Connecticut Building Code. The permit for the proposed work iSimsbury · 2026-10-23$2,500
- REAR 3 STORY ADDITION & RENOVATIONS TO CONVERT 1 FAMILY TO 3 FR & REAR STAIRS TO GRADECity of Norwalk · 2026-10-23$480,000
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 Connecticut came in between $5,850 and $129,000. We exclude permits under $1,000, jobs filed as whole-house construction, and counties whose building departments don't reliably report valuations.