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

In the unincorporated county, Permit Sonoma's PJR-133 Fence Guidelines address fences combined with retaining walls. Because fence height is measured from the lowest existing grade to the topmost point of the fence, a fence set on a retaining wall is measured from the bottom of the wall - the wall and the fence together cannot exceed the allowable fence height for that yard without the appropriate approval (administrative design review, design review, or a use permit). This prevents using a retaining wall to gain extra fence height in a required setback. Separately, retaining walls themselves are regulated as structures by the California Building Code as adopted by the county; a building permit is generally required for retaining walls that retain a surcharge or exceed the code threshold (commonly walls over 4 feet measured from the bottom of the footing to the top, or any wall supporting a surcharge). Engineered plans may be required for taller or surcharged walls. Retaining walls must also respect drainage, grading and setback rules and may trigger grading-permit review on sloped or hillside parcels. Because thresholds and setbacks vary by site and zoning district, confirm the specific requirements for your parcel with Permit Sonoma before building a wall or a fence-on-wall combination.