Pittsburgh, PA Fence Regulations: Retaining Walls (2026)

Under the PA Uniform Construction Code (Act 45 of 1999) as administered by Pittsburgh PLI, retaining walls not exceeding 4 feet in height measured from the lowest adjacent grade to the top of the wall are generally exempt from building permit requirements, unless the wall supports a surcharge load or impounds Class I, II, or III-A liquids. Retaining walls taller than 4 feet require a building permit and engineered drawings prepared by a licensed professional engineer registered in Pennsylvania. Pittsburgh's steep topography and three-river geography make retaining walls especially common in neighborhoods like Mount Washington, Polish Hill, and Troy Hill. The Zoning Code permits retaining walls in all districts as accessory structures provided they meet setback and design standards. Walls in the public right-of-way require a separate right-of-way permit from the Department of Mobility and Infrastructure (DOMI). Property owners should also verify whether the site is in a landslide-prone area, as Allegheny County maintains geologic hazard maps that may trigger additional engineering review.