Allegheny County, PA Fence Regulations: Retaining Walls (2026)

Allegheny County itself does not issue building permits for retaining walls. The Pennsylvania Uniform Construction Code (Act 45 of 1999, codified at 35 P.S. 7210.101) and its enabling regulations at 34 Pa. Code Chapter 403 apply countywide and adopt the International Residential Code and International Building Code. Section 403.62(a)(13) exempts a retaining wall that is not over 4 feet in height measured from the lowest level of grade to the top of the wall, unless the wall is supporting a surcharge or impounding Class I, II, or III-A liquids. A surcharge means any extra load behind the wall — a driveway, patio, building, fence, swimming pool, or steep slope above the wall — and a wall under 4 feet with a surcharge usually still requires a permit. The City of Pittsburgh codifies the same threshold in its PLI Work Not Requiring a Permit list and in Title 10 Building Code; walls over 4 feet, walls with surcharges, and any wall holding back fill from a structure typically require a residential building permit, plans stamped by a Pennsylvania-licensed professional engineer, and inspection. Each suburban municipality (Mt. Lebanon, Bethel Park, Ross Township, Penn Hills, Plum, Monroeville, McKeesport, etc.) administers UCC permits through its own building department or a third-party agency. Separately, Allegheny County Conservation District (ACCD) administers Pennsylvania's Erosion and Sediment Pollution Control Program under 25 Pa. Code Chapter 102 by delegation from PA DEP. A written E&S Plan is required for any earth disturbance of 5,000 square feet or more, and an NPDES Construction Stormwater Permit is required at 1 acre or more. ACCD review can be triggered by retaining walls cut into hillsides — a common condition in the Mon Valley and the Pittsburgh hills. Slope protection provisions in some municipal SALDOs allow an engineered retaining wall to satisfy slope stability requirements where slopes exceed 25 percent. Contact ACCD at 412-241-7645.