Longmont, CO Environmental Rules: Flood Elevation Requirements (2026)
Key Facts
- Freeboard
- 1 foot above base flood elevation
- Applies to
- New construction & substantial improvements
- Certification
- PE, architect, or land surveyor
- Nonresidential option
- Floodproof to same elevation
- Filed with
- Floodplain administrator
Summary
Longmont requires new and substantially improved residential structures in mapped flood zones to elevate the lowest floor one foot above the base flood elevation, certified by a licensed engineer or surveyor.
New construction and substantial improvement of any residential structure shall have the lowest floor (including basement), electrical, heating, ventilation, plumbing, and air conditioning equipment and other service facilities (including ductwork), elevated to one foot above the base flood elevation. Upon completion of the structure, the elevation of the lowest floor, including basement, shall be certified by a registered state professional engineer, architect, or land surveyor.
Full Breakdown
LMC § 20.20.020(A) requires new construction and substantial improvements of residential structures in special flood hazard areas to elevate the lowest floor, including basement, electrical, HVAC, and plumbing equipment, to one foot above the base flood elevation, Longmont's local freeboard standard above the FEMA minimum. A registered Colorado professional engineer, architect, or land surveyor must certify the as-built elevation to the floodplain administrator. Nonresidential structures under § 20.20.020(B) must meet the same one-foot freeboard or be certified watertight and floodproofed to that elevation. Manufactured homes and below-floor enclosures carry their own elevation and flood-vent standards in the same section.
Violations & Fines
Completing or occupying a structure without the required elevation certification violates § 20.16.060, treated as a separate daily offense and public nuisance enforceable by the city attorney.
Frequently Asked Questions
How much freeboard does Longmont require above base flood elevation?
Who certifies the elevation?
Sources & Official References
Other rules in Longmont
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Flood Elevation Requirements in Nearby Cities
How other cities in Boulder County handle flood elevation requirements.