In Antioch, building permits come from the city's Building Division, and its list of projects exempt from a permit includes retaining walls three feet or less in height. A wall taller than that isn't on the list, so we plan on a permit, pull it and line up the inspections. You can also call the division at 925-779-7065 with questions about what your project has to submit.
Where the wall sits on your lot matters here. The permit's site plan shows each retaining wall's location, size and distance from every property line. If any of the work reaches into the public right-of-way along the street, like a curb cut or a change to the driveway, the city's Engineering Division requires a separate encroachment permit for that part.
We're based in Antioch and work in the cities around it, from Concord and Walnut Creek out to Brentwood and Rio Vista. Most retaining wall calls we get are about sloped backyards, side yards that drop off and old timber walls that have started to lean. If you're not sure we cover your address, call and ask.