Fort Thomas planning panel proposes terracing rule for tall retaining walls

Planning staff in Fort Thomas proposed a UDO text change that would require retaining walls taller than six feet to be terraced or offset, a measure staff said follows common engineering practice to reduce the risk that an upper wall will fail onto a lower wall. Mark Stewart, the city’s building inspector and zoning administrator, presented the change during the Planning Commission’s June 17 public hearing.

The amendment would treat high retaining walls within the fences-and-walls chapter and add the terracing requirement—specifically, an offset equal to twice the height of the lower wall—so the upper wall does not undermine the lower one. Stewart said an engineer advised that the twice-height separation is a typical minimum rule of thumb, and he described previous cases where applicants sought 12-foot walls that would have created a shear condition for neighbors.

Commissioners questioned whether retaining walls should instead be classified as accessory structures (which would trigger setback requirements) and whether unique lot conditions could make the terracing requirement impractical. One commissioner noted that if a retaining wall is set back into the rear-yard setback it begins to look like a structure and would then be subject to structure setbacks; Stewart said applicants could seek a dimensional variance from the Board of Adjustment for height or setback relief and that engineering documentation could justify a narrower separation in extraordinary cases.

Staff and commissioners also discussed enforcement and plan review: walls taller than four feet generally require building permits and engineering, so design and safety would be evaluated during the permit review. The commission flagged that, because the proposed language would change what was advertised in the public hearing packet, staff may need to confirm with the city attorney or delay adoption on that particular amendment before forwarding to council.

If adopted, the requirement is intended to reduce structural risk and neighbor impacts from large single retaining walls in Fort Thomas’s tight-lot neighborhoods; applicants with unusual site constraints would be able to request relief through the Board of Adjustment with supporting engineering documentation.