Hesperia, CA Accessory Structures: ADU Rules (2026)

Hesperia Municipal Code Section 16.12.360 governs accessory dwelling units (ADUs) and Article 16.16 covers junior accessory dwelling units (JADUs). ADUs are permitted on lots zoned for agricultural, single-family, multi-family, or mixed use that contain an existing or proposed single-family or multi-family dwelling. Attached ADUs may not exceed 50 percent of the primary unit's floor area up to a maximum of 1,000 sq ft; detached ADUs are allowed up to 1,200 sq ft. JADUs are capped at 500 sq ft and must be contained entirely within an existing or proposed single-family residence. Minimum ADU size is 150 sq ft. Side and rear setbacks are 4 feet. Detached ADUs are generally limited to 16 feet in height, although California Gov. Code 66321(b)(4) requires Hesperia to allow 18 feet (near transit or on multi-family lots) or 25 feet (above-garage units) in qualifying situations - a discrepancy flagged by California HCD in its June 19, 2025 ordinance review letter. Hesperia is in the Mojave Desert / High Desert subregion of San Bernardino County, where ADUs are a primary tool for adding low-cost housing on the area's larger lot sizes.