Montebello, CA Accessory Structures: ADU Rules (2026)

Montebello Municipal Code Section 17.10.280 lets a property owner build a second, or accessory, dwelling unit in any residential zone without a conditional use permit, so long as the unit meets the section's design standards. In the R-2, R-3 and R-4 zones the unit is permitted by right if it meets the zone's general residential development standards, subsection B; in the R-A and R-1 zones it must instead meet twenty-two specific standards in subsection C. The lot may hold only one accessory unit in addition to the existing single-family home, item 1, and the unit must be clearly subordinate in size to that primary dwelling, whether attached within the existing living area or detached elsewhere on the same lot, item 2.

A detached unit must sit at least ten feet from the primary dwelling, or twenty feet if its entrance faces the primary home's rear, item 4. Size is capped by item 9: gross living area cannot be less than three hundred fifty square feet, and an attached unit cannot exceed thirty-five percent of the primary dwelling's existing living area, while a detached unit is capped at one thousand two hundred square feet. The unit needs its own off-street parking space with an enclosed garage door opening, item 11, and its architectural features, materials, color and roofline must match the primary dwelling, item 14.

Utilities are metered jointly with the primary unit, item 13, and the accessory unit's entrance cannot face the public right-of-way, item 16. Applications that fail these standards can be appealed to the city manager without a public hearing, subsection F.