Riverside County, CA Fence Regulations: Retaining Walls (2026)

The California Building Code requires a permit for retaining walls taller than 48 inches (4 feet) measured from the bottom of the footing to the top, or any height when supporting a surcharge. Riverside County Building and Safety applies a stricter 3-foot threshold locally in many cases and requires engineering for masonry or CMU walls in Seismic Design Category D — which covers essentially all of Riverside County near San Andreas and San Jacinto fault systems. Engineering must include drainage (weep holes or drain rock with filter fabric and a drain line), seismic loads, and soil-bearing analysis. Walls taller than 6 feet (plus cap) often require design by a licensed civil or structural engineer. Grading permits under Ordinance 457 may also apply if cut or fill exceeds 50 cubic yards or 3 feet in depth. Walls in hillside areas within the Ord. 348 Hillside Development Standards must use stepped or tiered designs to reduce visual mass. Walls in or near blue-line streams require Regional Water Quality Control Board review and can trigger SWPPP requirements under Ord. 555.