California ADU rules · Alameda County
Can I Build an ADU in Dublin?
Yes — you can build an ADU in Dublin. California's statewide ADU law requires every city, including Dublin, to approve a qualifying accessory dwelling unit by right, plus a junior ADU (JADU) on a single-family lot. What varies city to city are the local specifics below.
Can you build one?
ADUs allowed
CA state lawYes — by right
ADUs and JADUs are allowed by right in all residential and mixed-use zones; ministerial approval, no hearing.
Units on a single-family lot
CA state law1 ADU + 1 JADU
At least one ADU and one JADU per single-family lot (a conversion ADU may also be possible).
Units on a multifamily lot
Local ruleconversions (>=1 or 25% of units) + up to 2 detached (proposed multifamily) or up to 8 detached (existing multifamily), not to exceed number of existing units
City allows up to 2 detached ADUs on proposed multifamily lots and up to 8 detached on existing multifamily lots, not to exceed the number of existing units.
Junior ADU (JADU)
CA state lawAllowed
Up to 500 sq ft, within the walls of an existing single-family home (single-family lots only).
Size & height
Max detached ADU size
CA state law1,200 sq ft
Statewide default cap for detached new-construction ADUs in the absence of a compliant local ADU ordinance. The unconditional by-right floor a city must always allow is 800 sq ft (see Guaranteed minimum size); a city with a compliant ordinance may set its own ceiling.
Max attached ADU size
Local rulelesser of 50% of primary, 850 (studio/1-bed), 1,000 (2+ bed), or 1,200 if with new primary; state-exempt 800 always allowed
City sets a 1,200 sq ft cap for attached ADUs only if built with a new primary residence; otherwise, 50% of primary or state minimums apply.
Guaranteed minimum size
CA state law800 sq ft
An 800 sq ft ADU must be allowed regardless of FAR/lot-coverage caps; a city also cannot cap an attached ADU below 850 sq ft (1,000 for 2+ bedrooms).
Max JADU size
CA state law500 sq ft
Max height
Local rule16 ft
16 ft standard for detached; 18 ft if within ½ mile of major transit or for multifamily; attached ADUs up to 25 ft or base zone limit.
Setbacks
Side setback
Local rule4 ft
4 ft minimum for new construction; conversions may have zero setback if in same location.
Rear setback
Local rule4 ft
4 ft minimum for new construction; conversions may have zero setback if in same location.
Front setback
Local ruleADUs generally not permitted in front setback, except as needed to allow an 800 sq ft ADU with 4 ft setbacks
Front setback may be encroached only to guarantee state-minimum ADU rights.
Separation from main house
Local ruleNone required
No local minimum separation; only building/fire code applies.
Parking
Parking required
Local ruleUp to 1 space
1 off-street space per ADU (none for studios); multiple state exemptions apply.
Transit parking exemption
CA state lawYes — no parking required near transit & for conversions
No parking may be required within ½ mi walking distance of transit, in a historic district, for an ADU within an existing structure, within one block of car-share, or in certain permit-parking areas.
Garage-conversion replacement parking
Local ruleNot required
No replacement parking required when converting garage/carport/covered parking.
Approval, timeline & cost
Approval path
CA state lawMinisterial (by right)
No public hearing or discretionary design review for a qualifying ADU.
Approval timeline
CA state law60 days
The agency must act within 60 days of a complete application — and the ADU is deemed approved if it does not.
Owner-occupancy
Local ruleOnly for a JADU
Owner occupancy required only for JADUs; not for ADUs.
Impact-fee waiver
CA state lawWaived under 750 sq ft
An ADU of 750 sq ft or less pays no impact fees (the 750 sq ft threshold itself is exempt under § 66311.5); larger ADUs pay fees proportional to the primary dwelling. JADUs (≤ 500 sq ft) are exempt.
Permits required
CA state lawBuilding permit
Only a ministerial building permit — no conditional use permit or discretionary design review for a qualifying ADU.
Dublin allows up to 8 detached ADUs on existing multifamily lots and up to 2 on proposed multifamily, with no local separation requirement and no garage replacement. Attached ADUs may be up to 1,200 sq ft if built with a new primary residence.
Frequently asked questions
Can I build an ADU in Dublin?
Yes. California's statewide ADU law requires Dublin to approve a qualifying accessory dwelling unit ministerial (by right), plus a junior ADU (JADU) on a single-family lot.
How big can an ADU be in Dublin?
A detached ADU of at least 1,200 sq ft must be allowed, and an ADU of 800 sq ft can never be zoned out by floor-area or lot-coverage limits. A JADU can be up to 500 sq ft.
What are the setback requirements for an ADU in Dublin?
Side and rear setbacks are limited to 4 ft. ADUs generally not permitted in front setback, except as needed to allow an 800 sq ft ADU with 4 ft setbacks.
Is parking required for an ADU in Dublin?
Up to 1 space. No parking can be required within ½ mile of transit, for conversions, or for units inside the primary home. When a garage is converted, replacement parking is not required.
How long does ADU approval take in Dublin?
A complete application must be acted on within 60 days, with ministerial (by right) — no public hearing or discretionary design review for a qualifying ADU.
Do I have to live on the property to build an ADU in Dublin?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Dublin Municipal Code Chapter 8.80, as amended by Ord. 9-25 (November 2025)
- Dublin Municipal Code Chapter 8.80, as amended by Ord. 9-25 (2025)
- Cal. Gov. Code §§ 66310–66342 (ADU Law)
- HCD 2025 Accessory Dwelling Unit Handbook
- Cal. Gov. Code § 66317 (ministerial approval, 60-day deadline)
- Cal. Gov. Code § 66323 (by-right ADU/JADU, 800 sq ft, 4-ft setbacks)
- Cal. Gov. Code § 66333 (junior ADUs)
- Cal. Gov. Code § 66321 (size minimums & height)
- Cal. Gov. Code § 66322 (ADU parking; § 66334 covers JADU parking)
- Cal. Gov. Code § 66311.5 (impact fees: none for an ADU ≤ 750 sq ft or JADU ≤ 500 sq ft)
Last updated November 2025. This is an AI-assisted summary of Dublin's ADU rules, drawn from its published ordinance and California ADU law — general information, not legal advice, and it may be incomplete or out of date. Verify the controlling rule for your specific parcel with Dublin Planning before relying on it.
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