California: what the law actually says
Every claim below links to its primary source. Nothing here is asserted without one — see the disclaimer at the bottom.
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What is California's ADU law?
California's ADU law is Government Code Chapter 13, sections 66310 to 66342. It was added by SB 477 (Stats. 2024, ch. 7), effective March 25, 2024.
Source: Cal. Gov. Code § 66310 (leginfo.legislature.ca.gov), read 2026-10-16
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Must California ADU permits be approved without a hearing?
An ADU permit application must be considered and approved ministerially, without discretionary review or a hearing, notwithstanding variance and special use permit ordinances.
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How fast must a California agency say whether my ADU application is complete?
The permitting agency must tell you in writing whether your ADU application is complete within 15 business days of receiving it. If it is incomplete, the notice must list the missing items and how to fix them, and the agency may not later require an item that was not on that list.
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How long does a California agency have to approve or deny an ADU application?
Where there is an existing single-family or multifamily dwelling on the lot, the permitting agency must approve or deny a completed ADU application within 60 days, and if it has not, the application is deemed approved. If the ADU is filed together with a permit for a new home on the lot, the agency may wait until it decides that permit, and a delay you request pauses the 60 days.
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What happens if my California ADU application is denied?
If an ADU application is denied, the agency must return, in writing and within the same 60 days, a full list of the defective or deficient items and how to remedy them. If an application is found incomplete or is denied, the agency must also provide a process to appeal that decision in writing.
Source: Cal. Gov. Code § 66317(b) and (d)(1), read 2026-10-16
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Can a California city or county set a minimum lot size for ADUs?
A city or county may adopt an ADU ordinance with objective standards, but it may not set a minimum lot size. An ADU that is not converted from an existing structure may be required to sit no more than four feet from the side and rear lot lines.
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When must a California agency approve one ADU and one junior ADU on a lot?
A local agency must ministerially approve a building permit for one ADU and one junior ADU per lot with a proposed or existing single-family dwelling when the unit is within the existing or proposed space of the dwelling or an accessory structure (an expansion of up to 150 square feet beyond an existing accessory structure is allowed for ingress and egress), has exterior access, and has side and rear setbacks sufficient for fire and safety.
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When must a California agency approve a new detached ADU?
A local agency must also ministerially approve one new detached ADU on a lot with a proposed or existing single-family dwelling when it needs side and rear yard setbacks of no more than four feet. The agency may limit that unit to 800 square feet of livable space.
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When can a California agency not impose parking standards on an ADU?
A local agency may not impose parking standards on an ADU that is within one-half mile walking distance of public transit, is in a historic district, is part of the primary residence or an accessory structure, or is in the other cases listed in the statute. This applies whether or not the agency has adopted an ADU ordinance.
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Is a building permit required for an ADU in San Diego?
Permit path in San Diego: a building permit is required to create an ADU or JADU, with no exemptions.
Source: City of San Diego Development Services — ADU/JADU (fetched 2026-10-16)
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Which preapproved ADU plans does the City of San Diego accept?
The City of San Diego accepts three sets of preapproved ADU plans: County of San Diego Standard ADU Plans, City of Chula Vista Standard ADU Plans, and City of Encinitas Permit-Ready ADU Plans. Applications using them get a 30-day review and must still comply with the San Diego Municipal Code. You contact the plan provider yourself for the licensing cost.
Source: City of San Diego Development Services — Preapproved ADU Plans (fetched 2026-10-16)
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How do preapproved ADU plans work in the City of San José?
The City of San José lists vendors whose standard ADU plans it has preapproved. You still submit site-specific documents showing the location, utility connections and setbacks. Same-day permit issuance is available only if the lot is zoned residential with an existing single-family home or duplex and is not in a geohazard, landslide, flood or Wildland-Urban Interface zone.
Source: City of San José — Preapproved ADUs (fetched 2026-10-16)
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