North Hempstead, NY Environmental Rules: Flood Elevation Requirements (2026)

Chapter 21's construction standards set the Town's freeboard, the safety margin required above the federally mapped base flood elevation (BFE), the flood level with a one-percent annual chance of occurring. Under § 21-16A(1), new construction and substantial improvements in Zones A1-A30, AE and AH, and in Zone A where base flood elevation data exist, must have the lowest floor, including any basement or cellar, elevated to or above two feet above the base flood elevation. If no BFE data are published for a Zone A property, § 21-16A(2) instead requires the lowest floor to sit at least three feet above the highest adjacent grade.

In Zone AO, the lowest floor must clear the highest adjacent grade by at least two feet above the map's stated flood depth number, or two feet if none is shown. 1 requires new and substantially improved homes to be elevated on pilings, columns or shear walls so the bottom of the lowest horizontal structural member clears two feet above the base flood elevation, engineered to resist simultaneous wind and water loads. 2: instead of elevating, they may be floodproofed watertight to two feet above the base flood elevation if a licensed engineer or architect certifies the design.

Once the lowest floor is in place, the permit holder must submit an as-built elevation certificate, prepared and certified by a licensed land surveyor or professional engineer, to the Local Administrator before the Building Department signs off on the work.