Highland, CA Fence Regulations: Retaining Walls (2026)

The City of Highland regulates retaining walls on sloped ground through its hillside development section, HMC § 16.40.420. Subsection A applies the section to any lot or parcel with an average slope of 10 percent or greater as defined by the guidelines, and it exempts lots inside an approved tentative tract that was approved before the regulations were adopted. Where the hillside section and the fire safety regulations overlap, the fire safety regulations win unless the hillside provision is more stringent.

Subsection I covers walls and fences. Materials and colors must integrate with the structure, and the code strongly encourages naturally occurring rock. Long runs of wall are to be avoided by modulating the wall plane, placing tree wells, or adding pilasters or columns. Textured walls are required and smooth block walls are not permitted. Retaining walls should be designed to minimize visual impact through terracing, crib walls, and additional landscaping, and open view fencing is strongly encouraged to reduce impact from a point below.

The hard number is the height cap: maximum height shall be six feet. When a taller wall is required, the city can require two or more walls to create a terrace effect, with at least three feet of spacing between the walls and the area landscaped.

Hillside applicants file a natural features map and a conceptual grading plan with the initial application. The slope analysis and slope profiles must be stamped and signed by a registered landscape architect, civil engineer, or land surveyor, and the application also carries a geologic and soils report from a qualified soils engineering firm.

Walls on ordinary residential lots fall under HMC § 16.40.100(A)(2). A fence or wall not more than six feet in height, measured from the highest adjacent grade, is allowed along an interior side yard, rear yard or street side yard. Any retaining portion visible from the public right-of-way must be mitigated with a raised planter or a 2:1 landscape slope, as approved through a staff review permit or design review application.