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

The Siskiyou County Building Division states that a building permit is not needed for retaining walls that are not over four feet in height measured from the bottom of the footing to the top of the wall, unless the wall is supporting a surcharge. This matches the statewide exemption in the California Building Code (Section 105.2) and California Residential Code (Section R105.2), which exempt retaining walls up to four feet measured from the bottom of the footing, except where the wall supports a surcharge or impounds certain hazardous liquids. A surcharge is any added load above or behind the wall, such as a sloped backfill, a driveway, a structure, or a vehicle load; a wall under four feet that supports a surcharge still requires a permit. Walls over four feet, and any wall supporting a surcharge, require a building permit and engineered design. In Siskiyou County's hilly and mountainous terrain, retaining walls are common on sloped lots, and tiered or stacked walls may be reviewed together based on overall retained height. Setback and drainage considerations may also apply, and walls combined with fences can change permit triggers. Owners should confirm the height measurement method and surcharge status with the Building Division, and verify any zoning setback that applies to the wall location, before construction.