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

015(F)(4)(a) sets the elevation, or "freeboard," standard for residential construction inside Fullerton's mapped special flood hazard areas. In Zone AE, the lowest floor, including any basement, must be elevated at least one foot above the base flood elevation shown on the Flood Insurance Rate Map. In Zone AO, where the FIRM shows a flood depth number, the lowest floor must clear the highest adjacent grade by at least one foot above that depth number; if no depth number is shown, the minimum rises to three feet above the highest adjacent grade.

In Zone A, where no published base flood elevation exists on the FIRM, the lowest floor must reach or exceed the base flood elevation as determined by the City Engineer under division (C)(2)(d), using the best available federal, state or other data. Once construction is complete, the elevation of the lowest floor, including any basement, must be certified by a registered civil engineer or licensed land surveyor, and that certification is then verified by the Community Building Inspector before the Building Official will accept it.

Division (F)(4)(b) applies the same elevation benchmark to nonresidential structures but gives owners a floodproofing alternative: a nonresidential building may instead be floodproofed to or above the same elevation, with watertight walls and structural components able to resist hydrostatic and hydrodynamic loads, in place of physically raising the lowest floor. Manufactured homes get their own rule under division (F)(4)(c): the lowest floor must sit at or above one foot over the base flood elevation on a permanent, anchored foundation.