Islip, NY Fence Regulations: Retaining Walls (2026)

Wall standards are in Islip Town Code Section 68-406. Section 68-406A excepts an existing retaining wall from the general 6-foot fence-height cap. Section 68-406F provides that all walls greater than 18 inches in height from average, undisturbed grade must be set back from any property line a minimum of 4 feet or a distance equal to the height of the wall above average undisturbed grade, whichever is greater, and must obtain a permit prior to construction; for marine bulkheads a Town of Islip Wetlands and Watercourses Permit may constitute the required permit, subject to review by the Divisions of Building and Engineering. Section 68-406G provides that walls 18 inches or less in height do not require a setback or permit unless directed by the Town Engineer after a preliminary site assessment. All walls, as defined in Section 68-3, must receive a determination of the necessity of site plan review from the Divisions of Building and Engineering before construction.