Islip, NY Environmental Rules: Flood Elevation Requirements (2026)

Islip's freeboard standard sits inside Article XL, Flood Damage Prevention, first adopted March 17, 1987, and substantially rewritten by Local Law No. 9-2009 to track FEMA's Suffolk County Flood Insurance Study of September 25, 2009. The Commissioner of Planning and Development serves as local administrator under § 68-441A, reviewing floodplain development permit applications and requiring an as-built lowest-floor elevation certified by a licensed professional engineer or surveyor once construction is complete. In Zones A1-A30, AE and AH, and Zone A where base flood elevation data exist, § 68-442C(1) sets the lowest floor, including any basement, at two feet above base flood elevation.

Where Zone A has no base flood elevation data, § 68-442C(2) instead requires three feet above the highest adjacent grade, and Zone AO structures under § 68-442C(3) must sit at least two feet above the FIRM's mapped depth number. A 2017 amendment added § 68-442C(5), capping the lowest floor at no more than two feet above the required minimum so a homeowner cannot over-elevate beyond the standard. Coastal high-hazard Zones V1-V30, VE and V carry a parallel two-foot freeboard rule at § 68-442D(1), measured to the bottom of the lowest horizontal structural member on pilings or shear walls. Noncompliant construction is declared noncompliant and reported to FEMA under § 68-440E.