Ajo Fence Regulations: Retaining Walls Rules (2026)

Pima County Development Services requires building permits for retaining walls exceeding 4 feet in height from the bottom of the footing to the top of the wall, consistent with the adopted International Building Code (IBC). Walls over 4 feet must be designed by a licensed structural engineer or architect. The hillside development zone (HDZ) in the Catalina Foothills and Tanque Verde hillside areas imposes additional requirements for retaining walls related to grading, cut-and-fill limits, and visual impact. The HDZ may require retaining walls to be terraced rather than built as single tall structures, and wall surfaces must use natural-color materials that blend with the desert landscape. Drainage behind retaining walls must be properly designed to handle monsoon runoff -- weep holes or drainage systems are required. The Pima County Regional Flood Control District may review retaining walls in floodplain or drainage areas. Multiple retaining walls in a terraced configuration may trigger grading permit requirements. Walls supporting surcharges such as driveways, pools, or structures require additional engineering regardless of height.