San Marcos, CA Fence Regulations: Retaining Walls (2026)

105 of the Grading Chapter sets the trigger at three feet: any retaining wall measured from the top of its footing to the top of the wall that reaches or exceeds that height needs a Grading permit from the Administrative Authority, the City's grading/engineering division, unless the wall is instead permitted under a Building Permit. Below three feet, no grading permit is required at all. Once a wall is subject to the permit, the applicant must submit structural calculations and construction drawings stamped by an engineer registered in California, along with soil parameters and design factors of safety supplied by the project's Soils Engineer.

The one carve-out is a wall built in strict conformance with the San Diego Regional Standard Drawings (SDRSD), which can go up without custom calculations provided drainage still satisfies the Administrative Authority. Any wall over three feet must also include engineered drainage: continuous vertical and horizontal drains with filter protection for SDRSD-style walls, or, for segmented wall systems, permanent interceptors sized to divert a projected 100-year storm entirely away from the wall face. Segmented walls need Soils Engineer input specifically addressing hydraulic pressure buildup and backfill migration.

Walls with an exposed face over four feet must be earth-tone colored and textured for a natural appearance, and the City can require visual simulations before approval. Before the City will rely on the wall for issuing a Building Permit, both the Engineer of Record and the Soils Engineer of Record must certify in writing, with no disclaimer, that construction matches the approved plans, manufacturer requirements, and their own recommendations.