Alhambra, CA Accessory Structures: ADU Rules (2026)

040(B) permits ADUs on lots zoned for single-unit or multi-unit dwellings or mixed uses, with junior ADUs limited to single-unit lots. A single-unit lot can add one ADU plus one JADU; a multi-unit lot with existing units can add up to eight detached ADUs, capped at the number of existing units, or attached ADUs converted from non-livable space up to 25% of existing units. 040(D)(1) cap a detached ADU on a single-unit lot at 1,200 square feet; on a multi-unit lot, 850 square feet for a studio or one-bedroom and 1,000 square feet for larger units.

Attached ADUs cannot exceed 50% of the primary dwelling's floor area or the same 850/1,000 square-foot caps, whichever is greater. Setbacks require four feet at the side and rear for new attached or detached construction, with no setback required for conversions of existing living area or accessory structures, and a five-foot eave-to-eave separation between a detached ADU and other buildings. 040(F) is capped at two stories and 25 feet. 040(G) requires only one space per ADU, which can be tandem in an existing driveway, and no parking is required at all within a half mile of public transit, on a historic property, or when the ADU is carved out of the existing primary residence or an existing accessory structure.

Applications are reviewed ministerially by the Planning Division within 60 days, or 30 days for a pre-approved detached plan, and architecture must match the main dwelling's exterior materials, roofing and color unless the plan is city pre-approved.