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

City Code § 56-148F(1) sets the residential freeboard standard: within Zones A1-A30, AE and AH, and Zone A where base flood elevation data are available, new construction and substantial improvements must have the lowest floor, including any basement, elevated to or above two feet above the base flood level. Where no base flood elevation data exist in Zone A, § 56-148F(2) instead requires the lowest floor to sit at least three feet above the highest adjacent grade, and in Zone AO the lowest floor must be at least two feet above the FIRM's depth number, or two feet above grade if no depth number is shown, under § 56-148F(3).

Section 56-148G applies the same two-foot freeboard logic to nonresidential structures, but gives owners a choice: either elevate the lowest floor, including basement or cellar, to or above two feet above the base flood elevation, or floodproof the building so it is watertight below that same two-foot mark, with walls substantially impermeable to water and structural components able to resist hydrostatic and hydrodynamic loads. Any floodproofing route requires a licensed professional engineer or architect to design and certify the work, specifying the exact elevation, referenced to mean sea level, to which the structure is floodproofed.

Section 56-148D layers in general standards that apply regardless of elevation method: new construction must be anchored against flotation, collapse or lateral movement, built with flood-resistant materials, and any enclosed area below the lowest floor used for parking, access or storage must have flood vents meeting minimum opening-size criteria so hydrostatic forces equalize automatically during flooding.