California ADU rules · Los Angeles County
Can I Build an ADU in Arcadia?
Yes — you can build an ADU in Arcadia. California's statewide ADU law requires every city, including Arcadia, 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
Local rule1 detached ADU + 1 JADU per lot
Units on a multifamily lot
Local ruleConversions: up to 25% of existing units; Detached: up to 2 on proposed multifamily, up to 8 on existing multifamily, not to exceed 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
Local rule1,000 sq ft
1,000 sq ft for 2+ bedrooms; 850 sq ft for studio/1-bedroom
Max attached ADU size
Local rule850 sq ft for studio/1-bedroom; 1,000 sq ft for 2+ bedrooms; AND no more than 50% of primary dwelling; never less than 800 sq ft if all other standards are met
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
18 ft if within ½ mile of major transit stop or high-quality transit corridor; up to 20 ft for roof pitch alignment; attached ADU: up to 25 ft or primary dwelling height, whichever is lower
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
Local rule25 ft, unless this would reduce the ADU below 800 sq ft
No setback required for conversions in same location/dimensions as existing structure
Separation from main house
CA state lawNone required
No statewide separation requirement between the ADU and the primary dwelling.
Parking
Parking required
Local ruleUp to 1 space
Exemptions: within ½ mile of transit, historic district, conversions, on-street permit not offered, car share stop within 1 block; tandem/setback parking allowed
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 for garage/carport/covered parking conversion
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; JADUs require owner-occupancy in primary or JADU (except for government/land trust/housing org ownership)
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
Local ruleBuilding permit, ADU permit
Both permits required for all ADUs except certain conversions
Arcadia-specific factors that can change the answer
State law sets the floor, but these local conditions often decide whether a specific parcel works.
Sprinkler requirements
Sprinklers required in ADU only if required in primary dwelling; ADU does not trigger sprinklers in main house
Historic district parking exemption
No parking required for ADUs in historic districts; garage demolition for ADU does not require special notice unless in historic district
Arcadia caps detached and attached ADUs at 1,000 sq ft (2+ bedrooms) or 850 sq ft (studio/1-bedroom), with a 25 ft front setback unless it would reduce the ADU below 800 sq ft. No owner-occupancy is required for ADUs, but JADUs require it.
Frequently asked questions
Can I build an ADU in Arcadia?
Yes. California's statewide ADU law requires Arcadia 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 Arcadia?
A detached ADU of at least 1,000 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 Arcadia?
Side and rear setbacks are limited to 4 ft. 25 ft, unless this would reduce the ADU below 800 sq ft.
Is parking required for an ADU in Arcadia?
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 Arcadia?
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 Arcadia?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Arcadia Municipal Code § 9102.01.080 (Accessory Dwelling Units)
- Arcadia Municipal Code § 9102.01.080(B), (C)
- Arcadia Municipal Code § 9102.01.080(D)
- Arcadia Municipal Code § 9102.01.080(F)(1)
- Arcadia Municipal Code § 9102.01.080(F)(1)(B)-(C)
- Arcadia Municipal Code § 9102.01.080(E)(2)
- Arcadia Municipal Code § 9102.01.080(F)(3)
- Arcadia Municipal Code § 9102.01.080(F)(7)
- Arcadia Municipal Code § 9102.01.080(F)(7)(B)(3)
- Arcadia Municipal Code § 9102.01.080(E)(7)
- Arcadia Municipal Code § 9102.01.080
- Arcadia Municipal Code § 9102.01.080(E)(3), (E)(4)
- 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 § 66333 (junior ADUs)
- Cal. Gov. Code § 66321 (size minimums & height)
- Cal. Gov. Code § 66323 (by-right ADU/JADU, 800 sq ft, 4-ft setbacks)
- 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 2026-06-25. This is an AI-assisted summary of Arcadia'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 Arcadia Planning before relying on it.
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