Across 88 permits filed since 2025-03-10, the median is $125,000; half of projects fall between $74,250 and $221,250. 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 Nassau County, NY actually reported when they pulled permits.
Recent filings
- Construct 9'-10" wide x 4'-9" deep one story front addition over crawl space, new landing and steps and alterations to relocate stair to second floor and new front fenestration; in conjunction with electrical permit #20260352 Zoning VariancVillage of Malverne · 2026-09-04$50,000
- Construct 565 SF master bedroom and bath addition over existing first floorVillage of Garden City · 2026-08-31$150,000
- Construct a 575 sq. ft. second floor addition and 123 sq. ft. porch and steps in the Mulberry Avenue frontVillage of Garden City · 2026-08-26$220,000
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 Nassau County, NY came in between $74,250 and $221,250. 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
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