Cass County, MO Fence Regulations: Retaining Walls (2026)

" The retaining-wall trigger sits second on the county's twelve-item list: "Foundation walls and retaining walls supporting more than 48 inches (1219 mm) of unbalanced backfill that do not have permanent lateral support at the top or bottom" must be engineered. A separate item catches masonry construction at a lower threshold, "masonry foundation walls with an unbalanced backfill height greater that 4 feet," and other items in the same list trigger engineering for foundation walls under hydrostatic pressure, walls exceeding 9 feet from top to slab, footings placed on fill, foundations on slopes steeper than 4:1, foundations bearing partly on rock, foundation walls with an unbroken run over 25 feet, ICF foundation walls, long-span slabs over accessible space, log structures, and cold-formed steel framing.

Where the county's design-required list applies, the Building Codes Department will accept "a standard design approved by the Code Official" in place of a project-specific engineer's design, and for new single-family dwellings using a Code-Official-approved standard design, the sealing design professional must note the use of that standard design on the approved plans or in a separate report. A wall under the 48-inch backfill threshold, built with permanent lateral support, falls outside this engineered-design trigger, though the Building Codes Department still reviews it as part of the underlying building permit.