Dublin, CA Accessory Structures: ADU Rules (2026)

The City of Dublin regulates accessory dwelling units in Chapter 8.80 of its Zoning Ordinance, which the code states implements California Government Code sections 66310 through 66342. ADUs are reviewed ministerially rather than through a discretionary hearing. Section 8.80.030 requires the City to approve or deny a complete ADU permit application within 60 days, and the application is deemed approved if the deadline passes. Under Section 8.80.040, a detached ADU may not exceed 16 feet in height, increasing to 18 feet for a unit within one-half mile of public transit. The code allows a setback of no more than four feet from the side and rear lot lines for an ADU. An ADU must be a minimum of 150 square feet (or the size needed for an efficiency unit). Because California law preempts much of local ADU regulation, statewide caps generally limit ADUs to 850 square feet (one bedroom) or 1,000 square feet (two or more bedrooms) under the state-mandated minimums, and up to 1,200 square feet by local standard. One off-street parking space is generally required per unit, though studios are exempt and several state exemptions apply. A building permit is required for every ADU. The unit generally may not be sold separately from the principal residence except under Gov. Code 66341. Always confirm current standards with the Planning Division before designing a project.