St. Charles County, MO Fence Regulations: Retaining Walls (2026)

Under the Residential Code for One- and Two-Family Dwellings, adopted at St. Charles County Code Section 500.150, retaining walls not over four feet in height, measured from the bottom of the footing to the top of the wall, are exempt from a building permit unless the wall supports a surcharge, per Section R105.2, Item 3. Any retaining wall taller than four feet, or a shorter wall backing a slope, driveway or other load, needs a full permit from the Division of Building and Code Enforcement.

Under Section R106.1, construction documents must be prepared by a registered design professional when the Building Official requires it, and special site conditions can force a mandatory engineered design. The permit fee, set at Section 505.020(A)(2)(e)(8), is $100 or the estimated construction cost multiplied by the county's Permit Fee Multiplier, whichever is greater. Under Section R108.6, anyone who starts wall construction before the permit issues owes an added fee on top of the permit cost, though rough grading under 5,000 square feet and simple stakeouts are excepted.

Section R113.4 makes it a misdemeanor to build, alter or occupy in violation of an approved permit or the Building Official's directive, punishable by a fine of up to $500, with each day the violation continues counted as a separate offense. If the Building Official halts work with a stop-work order under Section R114.2, the owner or contractor must pay an administrative penalty of up to $250 before work resumes. Appeals of a retaining-wall permit decision go to the County Building Commission under Section R112.1, which follows the appeal procedure set out at Section 113 of the Building Code, Section 500.100.