Peoria, AZ Fence Regulations: Retaining Walls (2026)

Section 20-257 of the grading and drainage chapter defines a retaining wall as a vertical wall designed to retain earth or other material, measured from the top of the footing to the top of the wall. Once that wall exceeds 3 feet, the definition itself requires it to be designed by a civil or structural engineer and approved by the Community Development Department's Plans Review Division before construction can begin, independent of whether a building permit exemption applies. 2) uses a different threshold: it excuses retaining walls up to 40 inches, measured the same way from the top of the footing to the top of the wall, from needing a building permit at all.

That exemption disappears if the wall supports a surcharge, meaning extra load behind the wall such as a driveway or slope, or impounds Class I, II or IIIA liquids, in which case a permit is required no matter how short the wall is. Because the 40-inch permit exemption and the 3-foot (36-inch) engineering-design threshold are measured the same way but set at different heights, a wall between 36 and 40 inches needs an engineer's design under Section 20-257 even though it may not need a separate building permit under Section 18-21's exemption.

Property owners near Deer Valley Road face an added layer: Section 20-255(h) requires a Wall Permit before the City approves any minor land division, site plan, subdivision plat, or plot plan north of that road, covering any fence or wall for compliance with the chapter's drainage requirements, unless the Engineering Director waives it in writing after finding no drainage impact.