Hempstead, NY Hurricane Preparedness: Flood Elevation (2026)
Key Facts
- Enforcing agency
- Town of Hempstead Building Department
- Min. first-floor elevation
- 1.5 ft above groundwater table
- Flood wall standard
- Monolithic, waterproofed below 9 ft MSL
- Garage floor min.
- 6 in. above road crown at entrance
- First-offense penalty
- $500 to $2,500 fine or 15 days jail
Summary
Before the Building Department will approve construction, a new Hempstead dwelling's first floor must sit at least one and a half feet above the local groundwater table, and any exterior wall built below nine feet above mean sea level must be solid, opening-free monolithic construction that is fully waterproofed. Garage floors and street grading carry their own elevation minimums.
No person shall erect any dwelling within the Town of Hempstead having a first floor elevation less than 1 1/2 feet above the highest level of the groundwater table for the location of such dwelling or dwellings as determined from the records of the Nassau County Department of Public Works. All exterior walls of any such dwelling below the elevation of nine feet above mean sea level on any building plot, the grade of which is not wholly above the elevation of nine feet above mean sea level, shall be of monolithic construction without openings, and all such walls and floors below the elevation of nine feet shall be properly waterproofed with a waterproofing material approved by the Building Department.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: rev 4863878; v67 updated 2026-04-28; through 04-28-2026).
Full Breakdown
Chapter 86, Building Construction Administration, Section 86-9E, sets the flood-resistant elevation standards the Building Inspector checks before issuing a permit or certificate of occupancy. The first-floor elevation of any dwelling must clear the highest recorded groundwater table for that lot, as shown in Nassau County Department of Public Works records, by at least one and a half feet. Any exterior wall standing below the nine-foot mean-sea-level line must be built of monolithic construction without openings and waterproofed with a Building Department-approved material, and a flat-slab dwelling built without a cellar or crawl space must set its slab at least 18 inches above the crown of the adjoining road, or nine feet above sea level, whichever is higher.
Attached garages get their own rule: the floor must sit at least six inches above the highest point of the road crown at the entrance, with a concrete curb to stop street runoff and a floor sloped toward the entrance for drainage, though the Superintendent of Highways, Town Engineer and Building Department manager can jointly waive that rule for hardship cases. 5 feet above mean sea level before a building permit issues, unless the owner posts a performance bond to grade or install the street to that height.
Violations & Fines
Building without an approved permit or below the required elevations is a Chapter 86 violation under Section 86-25: a first offense carries a fine of $500 to $2,500 or up to 15 days in jail, a second offense within five years rises to $1,500 to $5,000, and a third or later offense within five years reaches $3,000 to $10,000, with each day the violation continues counted as a separate offense.
Frequently Asked Questions
How high above the groundwater table must a Hempstead home's first floor be?
What construction is required for walls below the nine-foot flood line?
Are garages held to the same elevation rule?
What happens if I skip these elevation requirements?
Sources & Official References
Other rules in Hempstead
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