California ADU rules · Contra Costa County
Can I Build an ADU in Moraga?
Yes — you can build an ADU in Moraga. California's statewide ADU law requires every city, including Moraga, 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
Local ruleConditional
Ministerial (by-right) for ADUs/JADUs meeting objective standards; discretionary (conditional use permit) if standards not met.
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
Only 2 detached ADUs allowed per multifamily lot, not 4 or 8.
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 rule50% of primary, <=850 (1 bed) or <=1,000 (2+ beds); 800 sq ft cap if lot exceeds max floor area
Attached ADUs: 850/1,000 sq ft max, but cannot exceed 50% of primary; 800 sq ft cap if lot is over max FAR.
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
Max 16 ft within 10 ft of property line; up to 19 ft elsewhere on lot.
Setbacks
Side setback
CA state law4 ft
A city cannot require more than 4 ft side or rear setback; conversions of existing structures are exempt.
Rear setback
CA state law4 ft
Front setback
CA state lawNo front setback may block the mandatory 800 sq ft / 16-ft / 4-ft-setback ADU; otherwise per base zone
Separation from main house
Local ruleNone required
No explicit separation required if setbacks and fire safety are met.
Parking
Parking required
Local ruleUp to 1 space
1 off-street space per ADU; exemptions for transit, conversions, historic, car share, etc.
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
CA state lawNot required
When a garage/carport is demolished or converted to build an ADU, replacement parking cannot be required.
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
No owner-occupancy for ADUs; required for JADUs.
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.
Moraga-specific factors that can change the answer
State law sets the floor, but these local conditions often decide whether a specific parcel works.
Hillside development permit exemption
Ministerial ADUs are exempt from hillside development permit requirements; discretionary ADUs are not.
Historic district
Historic district rules may apply for demolition/alteration of structures for ADUs.
Moraga caps ministerial detached ADUs at 800 sq ft and allows only 2 detached ADUs on multifamily lots. Ministerial ADUs are exempt from hillside development permits.
Frequently asked questions
Can I build an ADU in Moraga?
Yes. California's statewide ADU law requires Moraga 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 Moraga?
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 Moraga?
Side and rear setbacks are limited to 4 ft. No front setback may block the mandatory 800 sq ft / 16-ft / 4-ft-setback ADU; otherwise per base zone.
Is parking required for an ADU in Moraga?
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 Moraga?
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 Moraga?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Moraga Municipal Code Chapter 8.124 (ADUs & JADUs), Ord. No. 309, § 5(Exh. B, 11), 5-10-2023; Ord. No. 296, § 3, 4-14-2021
- Moraga Municipal Code §§ 8.124.100, 8.124.120, 8.124.180
- Moraga Municipal Code § 8.124.110
- Moraga Municipal Code § 8.124.130.H
- Moraga Municipal Code § 8.124.130.E
- Moraga Municipal Code § 8.124.130.A
- Moraga Municipal Code § 8.124.130.K
- Moraga Municipal Code §§ 8.124.100.C, 8.124.110.B.2
- Moraga Municipal Code § 8.124.080.A
- Moraga Municipal Code § 8.124.090
- Cal. Gov. Code §§ 66310–66342 (ADU Law)
- HCD 2025 Accessory Dwelling Unit Handbook
- 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 § 66314 (local ordinance standards)
- Cal. Gov. Code § 66317 (ministerial approval, 60-day deadline)
- Cal. Gov. Code § 66311.5 (impact fees: none for an ADU ≤ 750 sq ft or JADU ≤ 500 sq ft)
Last updated 2026-06-25. This is an AI-assisted summary of Moraga'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 Moraga Planning before relying on it.
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