Arcadia, CA Accessory Structures: ADU Rules (2026)
ADU rules in Arcadia, CA, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- Review type
- Ministerial, no discretionary review or hearing
- Decision deadline
- 60 days from a completed application
- Detached ADU height
- 16 feet; 18 feet near major transit; 20 feet for roof pitch
- Building-permit-only detached ADU
- Four-foot side and rear setbacks, 800 square feet or smaller
- ADU permit size cap
- 850 square feet studio/one-bedroom; 1,000 square feet two-plus bedrooms
- Front setback (ADU permit)
- 25 feet
- Section
- Arcadia Municipal Code § 9102.01.080
Summary
In the City of Arcadia, California, an accessory dwelling unit is approved ministerially, without discretionary review or a hearing, under Arcadia Municipal Code § 9102.01.080. The city must approve or deny a completed application within 60 days. A detached ADU is capped at 16 feet in height, and a building-permit-only detached ADU needs side and rear setbacks of at least four feet.
A.Purpose. ... The purpose of this section is to allow and regulate accessory dwelling units (ADUs) and junior accessory dwelling units (JADUs) in compliance with Chapter 13 of Division 1 of Title 7 of the California Government Code. ... 3.Process and Timing. A.An ADU permit is considered and approved ministerially, without discretionary review or a hearing.B.The city must approve or deny an application to create an ADU or JADU within 60 days from the date that the city receives a completed application. ... 2.Height. ... A.Except as otherwise provided by subsections (E)(2)(B) and (E)(2)(C) below, a detached ADU created on a lot with an existing or proposed single family or multifamily dwelling unit may not exceed 16 feet in height.
Full Breakdown
Section 9102.01.080 of the Arcadia Development Code regulates both accessory dwelling units (ADUs) and junior accessory dwelling units (JADUs). Four scenarios need only a building permit. On a single-family lot, one converted ADU and one JADU are allowed inside existing or proposed living space, or inside an existing accessory structure plus up to 150 additional square feet for ingress and egress. A limited detached new-construction ADU on a single-family lot needs side and rear setbacks of at least four feet and a total floor area of 800 square feet or smaller. On a multifamily lot, converted ADUs in storage rooms, boiler rooms, passageways, attics, basements or garages are allowed up to 25 percent of the existing units, with at least one always allowed. A proposed multifamily building can add two detached ADUs, and an existing one up to eight, but never more than the number of primary dwelling units on the lot.
Everything else needs a building permit and an ADU permit. Those ADUs are capped at 850 square feet for a studio or one-bedroom and 1,000 square feet for two or more bedrooms, and an attached ADU is limited to 50 percent of the primary dwelling's floor area. No ADU may push the lot's floor area ratio above 45 percent, and the city cannot force any ADU below 800 square feet. Setbacks are four feet on the sides and rear and 25 feet in front. Lot coverage tops out at 45 percent for a one-story primary dwelling and 35 percent for a two-story one, and open space cannot fall below 50 percent.
Detached ADUs stop at 16 feet. The limit rises to 18 feet within one-half mile walking distance of a major transit stop or high quality transit corridor, and to 20 feet when needed to match the primary roof pitch. Attached ADUs may reach 25 feet or the zone limit, whichever is lower, and never more than two stories. Fire sprinklers are required in the ADU only when the primary residence must have them. If the city denies an application, it must send a list of every deficient item within the same 60-day window.
Violations & Fines
A use or structure that breaks the Development Code is declared a violation and a public nuisance under § 9108.15.070, and a violator is guilty of a misdemeanor punishable under Municipal Code Section 1200. City Code Services Staff start enforcement with a written Notice of Violation. Willful violations carry a civil penalty under the Fee Schedule for each day the violation continues. For a JADU that breaks its recorded deed restriction, the city can seek an injunction or abatement of the illegal unit.
Frequently Asked Questions
How long does the City of Arcadia have to decide an ADU application?
How tall can a detached ADU be in the City of Arcadia, California?
Does an Arcadia ADU need a hearing before the Planning Commission?
What setbacks apply to a new detached ADU in Arcadia?
Sources & Official References
Other rules in Arcadia
How Arcadia compares: Easiest Cities to Build an ADU·California rules heatmap·Compare Arcadia to another location·View the California accessory structures overview
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ADU Rules in Nearby Cities
How other cities in Los Angeles County handle adu rules.