Nashua, NH Environmental Rules: Flood Elevation Requirements (2026)
Key Facts
- Freeboard above BFE
- 1 foot (residential lowest floor)
- Nonresidential option
- 1-2 ft elevate or floodproof
- Zones covered
- A, AE, AO
- Enforcing office
- Dept. of Building Safety
- Proof required
- FEMA Elevation Certificate
Summary
New and substantially improved homes in Nashua flood zones must sit at least one foot above the 100-year flood elevation, a one-foot freeboard above FEMA's base flood level.
All new construction or substantial improvement of residential structures have the lowest floor (including basement) elevated at least one foot above the 100-year flood elevation.
(2) That all new construction or substantial improvements of nonresidential structures have the lowest floor (including basement) elevated at least one or two feet above the one-hundred-year flood level depending on the Flood Design Class (one foot for Flood Design Classes 1, 2 and 3 and two feet or the 500-year flood elevation, whichever is higher for Flood Design Class 4) or to the design flood elevation, whichever is higher or, together with attendant utility and sanitary facilities, shall:
(a) Be floodproofed so that below the one-hundred-year flood elevation the structure is watertight with walls substantially impermeable to the passage of water;
(b) Have structural components capable of resisting hydrostatic and hydrodynamic loads and the effects of buoyancy; and
(c) Be certified by a registered professional engineer or architect that the design and methods of construction are in accordance with accepted standards of practice for meeting the provisions of this section.
(3)
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: rev 4805762; v29 updated 2026-02-10; through 02-10-2026).
Full Breakdown
Under the City of Nashua Floodplain Development Ordinance, the Administrative Officer sets the 100-year flood elevation for each site from FEMA's Flood Insurance Study and FIRM, or from best-available data in unmapped Zone A. New construction or substantial improvement of a residential structure in Zones A, AE, or AO must have its lowest floor, including any basement, elevated at least one foot above that elevation. Nonresidential buildings face the same one-foot minimum (or two feet for higher Flood Design Classes), or must be floodproofed and engineer-certified instead. Section 190-63 separately requires that a residential structure's mechanical and utility equipment sit at least one foot above base flood elevation so it isn't submerged during a flood event.
Violations & Fines
Development without the required elevation is a code violation; owners must furnish a FEMA Elevation Certificate to the Department of Building Safety, and a structure lacking one is presumed noncompliant until documentation is provided.
Frequently Asked Questions
How high above base flood elevation must a new Nashua home be built?
Do manufactured homes get the same freeboard requirement?
Sources & Official References
Other rules in Nashua
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