Westminster, CO Fence Regulations: Retaining Walls (2026)

Westminster sets the same three-foot line for two different retaining wall requirements, and they're easy to confuse. from the grade level on the low side to the top of wall," but that exemption disappears the moment the wall supports a surcharge of earth, a structure, or impounds Class I, II, or IIIA flammable liquids, meaning even a two-foot wall in those situations needs a permit. The second is the design-stamp trigger under Section 11-9-3(C)(3)(b)(iii): any retaining wall over three feet, measured the same way, from the low-side grade to the top of the wall, needs plans, engineering calculations, and other submittal data bearing the seal of a Colorado-licensed architect or engineer before the Building Official will approve it.

The application itself has to include a site plan showing the wall's location and, where structural work is involved, computations sufficient for the Building Official to verify compliance, per Section 11-9-3(C)(1)-(2). Zoning rules layer on top of the building code: under Section 11-4-6(P)(3)(c), a fence built on top of a retaining wall is height-limited separately, measured from the ground on the high side of the wall to the top of the fence. And under Section 11-4-6(P)(7), retaining walls built within a vehicular sight triangle must meet City standard design specifications, and any wall the traffic engineer finds obstructs driver visibility can be ordered abated as a nuisance under Title VIII, Chapter 4. Skipping the required permit carries the same financial penalty as any other unpermitted building work under Section 11-9-3(E)(5).