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

Permit Sonoma's policy document BPC-005, 'When Is a Building Permit Not Required?' (version 05/26/2023), lists work exempt from a building permit in unincorporated Sonoma County, drawing on California Building Code Appendix Chapter 1 and Chapter 7 of the Sonoma County Code. Retaining walls are exempt only if they 'retain not more than 3 feet of material' and do not support a surcharge or impound class I, II, or IIIA liquids. Any wall retaining more than 3 feet of material, or any wall of any height that supports a surcharge (such as a slope, driveway, or structure bearing on the retained material), requires a building permit through Permit Sonoma. The companion fence policy, BPC-023 'Fence Requirements,' adds that a building permit is required for all solid wood, concrete, and masonry fences exceeding 7 feet in height and for all fences, regardless of construction, exceeding 10 feet in height; fences exceeding 8 feet must be designed by an architect or engineer. Permit Sonoma also cautions that exemption from a building permit does not waive other approvals that may apply, such as use permits, design review, or coastal permits.