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

Retaining walls in unincorporated Mono County are addressed in the General Plan Land Use Element development standards. Section 04.120 provides that retaining walls of four feet or less above grade are permitted within required setbacks, meaning a short retaining wall can be built in a yard area that would otherwise need to stay clear of structures. For walls exceeding 4 feet, the base of the wall shall be placed at least as far from the property line as the wall exceeds 4 feet, a stepped setback rule that keeps taller earth-retaining structures away from boundaries. Beyond zoning, retaining walls are also regulated for structural safety under the California Building Code, which Mono County administers; walls retaining more than a set height of soil, or supporting a surcharge such as a driveway or slope, typically require engineering and a building permit. Because Mono County terrain is mountainous, with steep lots, snow loads, and seismic considerations, retaining-wall design often needs professional review. These are county standards for unincorporated land; the Town of Mammoth Lakes applies its own code within town limits. Confirm exact thresholds with the Mono County Community Development Department before construction.