Santa Cruz County, CA Fence Regulations: Retaining Walls (2026)

315(A)(4), part of the county's exempt-work list under the adopted 2025 California Building Code, exempts retaining walls from the building-permit requirement only when they retain three feet of material or less, and only if they are not supporting a surcharge or impounding Class I, II, or III-A liquids; walls carrying either of those loads need a permit regardless of height. The same subsection then draws a separate, higher line for engineering: unless the Building Official specifically exempts it, any retaining wall retaining more than four feet of material must be designed by an engineer licensed by the State of California.

That leaves a middle band, walls retaining more than three feet but four feet or less, that require a building permit but not necessarily a licensed engineer's design unless the Building Official determines one is needed. 315. Because retaining walls sit at grade changes common on the county's steep coastal-terrace and Santa Cruz Mountains lots, the height thresholds matter for anyone regrading a hillside parcel; a wall built to hold back a driveway cut or a septic leach-field terrace on sloped ground routinely crosses the four-foot engineering line even when it looks modest from the street.