Loudoun County, VA Environmental Rules: Flood Elevation Requirements (2026)

I sets the construction standards that apply once a project is inside the Floodplain Overlay District's Major Floodplain. a requires new construction or substantial improvement of any residential structure, including manufactured homes, to have its lowest floor -- basement included -- elevated to or above base flood elevation (BFE), and recommends a one-foot freeboard safety margin above that line. b: they may be flood-proofed instead of elevated, provided every component below one foot above BFE is watertight, resists hydrostatic and hydrodynamic loads and buoyancy, and a licensed professional engineer or architect certifies the design meets that standard, with the certification retained by the Floodplain Administrator.

2. All new construction and substantial improvements must also be anchored against flotation, collapse, or lateral movement under Codified Ordinances Chapter 1410, and utilities, ductwork, and sewage systems must be positioned to prevent floodwater infiltration. 3 requires the applicant to submit the lowest-floor elevation and the base flood elevation for that specific lot, giving the Floodplain Administrator the numbers needed to confirm compliance before construction starts.