Plymouth, MN Fence Regulations: Retaining Walls (2026)

Plymouth's fence and wall regulations single out retaining walls for extra safety oversight. Under City Code Section 21130.01, Subd. 4(g), a retaining wall cannot be placed within any drainage or ponding easement unless the City Engineer has separately reviewed and approved it, protecting the City's stormwater infrastructure from encroachment. Subd. 4(i) then requires a companion safety fence: any retaining wall exceeding four feet in height, and any tiered retaining wall that requires a building permit, must have a fence at least three and one-half feet tall installed on top of it. The Zoning Administrator can grant an exception to this fence requirement only if the retaining wall itself does not pose a public safety concern, meaning the default is that the fence goes on unless the City affirmatively waives it.

Because retaining walls are regulated inside the same section as fences, the general provisions of Subd. 4 apply on top of the specific rules: the wall must stay out of any wetland or required wetland buffer, cannot cross a required rain garden, filtration basin or infiltration basin, and cannot extend below the ordinary high water level of a lake, stream or water quality pond under Subd. 4(j). A certificate of survey may also be required under Subd. 4(f) for any wall built on or within six feet of a property line, unless the corner stakes are already marked and a survey is on file with the City. Retaining walls over four feet that require a building permit are reviewed under Section 1015 of the City Code alongside the fence-on-top requirement.