Brentwood, CA Fence Regulations: Retaining Walls (2026)

008(I) sets the standard for retaining walls citywide: no individual retaining wall may exceed 4 feet in height. If the embankment being retained is taller than that, the code requires the slope to be benched so that no single wall in the series tops 4 feet above finished grade, with at least a 2-foot horizontal gap between each bench. The city will consider a taller single wall only as an exception, and only when the chief building official or public works director approves it based on a geotechnical report from a licensed civil or geotechnical engineer showing the slope or soils require it.

A building permit is required whenever a retaining wall exceeds 4 feet, measured from the bottom of the footing to the top of the wall, and also whenever the wall supports a steeply sloped surface the code calls a surcharge, regardless of the wall's own height. Property owners planning a hillside retaining system should design it as a series of shorter, terraced walls rather than one tall wall: the code's own illustration favors terraced walls because they break up the visual mass and are easier to screen with landscaping, while a single wall over 4 feet creates what the code calls a massive scar on the hillside.