Flagstaff, AZ Fence Regulations: Retaining Walls (2026)

Section 10-30.60.040 (Natural Features and Site Drainage) governs how retaining walls look and how tall they can be. Walls must be built with native rock or masonry, such as split-face block or scored and textured concrete, that reads as a traditional rock wall rather than a plain poured or block wall. Any retaining wall that is exposed or visible from a public right-of-way is capped at five feet in height where feasible; when a taller wall is needed to hold a cut or fill slope, the code requires a series of terraced or stepped walls instead of one tall wall, or a building placed to screen the cut slope from the right-of-way.

Each terrace in a stepped wall system must be at least three feet wide. Separately, the City's local amendment to the International Building Code, adopted at Section 4-02-001-0001, requires an Arizona Registered Design Professional (architect or engineer) to design any retaining wall that carries an imposed surcharge from adjacent structural elements or unbalanced loading and exceeds four feet, with drawings sealed and submitted at the time of permit application. A homeowner building a plain, unloaded garden wall under four feet generally avoids the design-professional requirement, but taller or surcharged walls need both an engineered plan and a building permit from the Building Safety Section before construction.