Biloxi, MS Fence Regulations: Retaining Walls (2026)

Harrison County and its cities regulate retaining walls under the adopted International Residential Code and International Building Code. Walls 4 feet or less in height, measured from bottom of footing to top of wall, typically do not require a building permit unless supporting a surcharge. Walls over 4 feet require a building permit and structural drawings stamped by a Mississippi-licensed professional engineer. Surcharge loads from driveways, structures, or sloped backfill above the wall lower the permit-free threshold — any wall retaining a slope over 1:1 or supporting a structure requires engineering regardless of height. Harrison County's coastal soil profile — sandy fill, variable water table, and high seasonal rainfall — makes drainage design critical; walls without proper weep holes, gravel backfill, and drain tile commonly fail. Setbacks from property lines typically match zoning fence setbacks (3 to 5 feet). Walls in FEMA floodplains or within the MS Coastal Wetlands zone (§49-27) may require additional permits from the Mississippi Department of Marine Resources.