Cupertino, CA Environmental Rules: Flood Elevation Requirements (2026)

043 requires new construction, substantial improvements, and reconstruction after substantial damage to residential structures to set the lowest floor, including basement, machinery, and equipment floors, at least one foot above the base flood elevation in AE, AH, and A1-30 zones. In an AO zone the lowest floor must clear the highest adjacent grade by one foot above the depth number shown on the Flood Insurance Rate Map, or by at least three feet above grade if no depth number is listed; in an unnumbered A zone without a mapped base flood elevation, the same one-foot freeboard applies once the Floodplain Administrator determines the elevation.

A registered civil engineer or licensed land surveyor must certify the completed lowest-floor elevation, and the community building inspector must verify it before the Floodplain Administrator will accept it. Nonresidential structures may instead be floodproofed below that elevation so the building is watertight, with structural components able to resist hydrostatic and hydrodynamic loads, certified by a registered civil engineer or architect. Any fully enclosed area below the lowest floor used only for parking, storage, or access must have flood openings that automatically equalize hydrostatic pressure: non-engineered openings need at least two openings on different walls totaling one square inch of net area per square foot of enclosed area, with the bottom of each opening no higher than one foot above grade.

Detached garages and small accessory structures may sit below the base flood elevation only if built with flood-resistant materials, anchored against flotation, and designed for automatic floodwater entry.