La Grange, MO Environmental Rules: Flood Elevation Requirements (2026)

Section 405.040(B) of the La Grange City Code sets the specific elevation standard that applies once base flood elevation data exists for a site under Section 405.040(A)(2). Residential structures, including manufactured homes, must have the lowest floor elevated to one foot above base flood elevation, giving La Grange one foot of freeboard above the FEMA-mapped elevation. Non-residential buildings, such as commercial or industrial structures, may either meet that same one-foot freeboard standard or be floodproofed below the base flood elevation so the structure is watertight with walls substantially impermeable to water and components able to resist hydrostatic and hydrodynamic loads; a registered professional engineer or architect must certify that floodproofing standard and file the certification with the Floodplain Administrator under Section 405.030(C)(9).

Fully enclosed areas below the lowest floor used only for parking, building access or storage must have at least two openings with a combined net area of one square inch per square foot of enclosed area, with the bottom of each opening no higher than one foot above grade, so floodwaters can automatically enter and exit rather than build hydrostatic pressure on the walls. Manufactured homes get a parallel rule: the lowest floor must sit one foot above base flood elevation, or, in an existing manufactured home park not otherwise covered, the chassis may instead rest on reinforced piers at least thirty-six inches above grade.