State ADU law
California ADU laws: what every city must allow
California has the most detailed ADU statute in the country. Here is what it makes every city and county do, cited to the section.
What to do next: use this research to check your own lot and bids, then tell us about your project. Matching is not live yet, so we reply with information, not a quote.
Get ADU optionsWritten by HyreADU Research Desk Primary-source statute research
The short answer
California ADU laws require every city and county to approve qualifying ADUs and junior ADUs under state standards, within 60 days of a complete application. The rules sit in Government Code sections 66314 to 66342.
A city may not require the owner to live on the lot for an ADU (§ 66315).
It may not cap ADU size below 850 square feet, or 1,000 square feet for more than one bedroom (§ 66321(b)(2)).
Parking may not exceed one space per unit or bedroom, and none can be required within half a mile walking distance of public transit (§§ 66314(d)(10), 66322(a)).
ADUs under 750 square feet are exempt from impact fees (§ 66324(c)(1)). These are floors. Your city can be more generous, and it still sets design rules the statute allows.
What California law requires of cities
Each row is the rule as the HCD ADU Handbook states it, with the Government Code section it cites.
| Question | What the California statute says | Citation |
|---|---|---|
| Must the city allow ADUs at all? | Yes. Section 66323 lists four kinds of ADU a city must approve, including one converted ADU and one JADU per single-family lot, and one new detached ADU of up to 800 square feet with four-foot side and rear setbacks. | Gov. Code § 66323(a)(1)–(4) |
| How fast must the city act? | It must approve or deny a complete application within 60 days. If it denies, it must give a written list of defects and how to fix them within the same 60 days. | Gov. Code § 66317(a), (b) |
| Can the city require the owner to live there? | Not for an ADU. No standard beyond § 66314 may be imposed, “including an owner-occupant requirement.” The city may require rentals of 30 days or longer. | Gov. Code § 66315 |
| What size must the city allow? | A local maximum cannot be below 850 square feet, or 1,000 square feet for an ADU with more than one bedroom. Without a compliant ordinance, a new detached ADU may be up to 1,200 square feet. | Gov. Code §§ 66321(b)(2), 66314(d)(4) |
| How tall? | A detached ADU gets a base height of 16 feet, rising to 18 or 20 feet in conditions set out in the statute. | Gov. Code § 66321(b)(4) |
| Parking? | No more than one space per unit or bedroom, whichever is less, and tandem on a driveway counts. None may be required within half a mile walking distance of public transit, among other exemptions. A garage converted to an ADU need not be replaced. | Gov. Code §§ 66314(d)(10)–(11), 66322(a) |
| Impact fees? | None on an ADU under 750 square feet. At 750 square feet or more, fees must be proportional to the ADU’s size against the main home. | Gov. Code § 66324(c)(1) |
| Fire sprinklers? | Building an ADU cannot trigger a sprinkler requirement in the existing house. | Gov. Code § 66314(d)(12) |
California ADU rules set by state law, as read on the official statute page on October 27, 2026.
Who the law covers and when it took effect
The rules apply to every city and county in California, including charter cities. The HCD Handbook we read describes the law as amended by legislation in effect on January 1, 2025.
SB 477 (Stats. 2024, Ch. 7) moved the ADU law out of the old section 65852.2 into sections 66310 to 66342, so older city documents may cite numbers that no longer exist. Our owner-occupancy study tracks a later 2026 renumbering and the junior ADU changes.
What is still up to your city or county
Your city still sets objective design standards, such as materials, rooflines and landscaping, as long as they do not block the units section 66323 guarantees. It can allow more than the state floor: bigger units, taller units, less parking.
Coastal zone, historic district and fire hazard rules can add review. Utility connection rules and building code apply in full. Fee schedules, which are not set by state law, are covered in our California ADU fees by city research.
How to check your own city
Answer these in order, in writing, before you pay for drawings.
- 1 Find your city’s ADU ordinance and its adoption date
An ordinance older than January 2025 may contain clauses state law now overrides. Section 66316 makes a non-compliant ordinance null and void, and state standards then apply.
- 2 Ask which section 66323 category your plan fits
A 66323 unit skips lot coverage, front setback and design standards. Ask the counter to confirm in writing.
- 3 Check transit distance for parking
Measure walking distance to the nearest public transit stop. Within half a mile, no parking can be required.
- 4 Ask for the date the 60-day clock starts
The clock runs from a complete application. Get written confirmation of the completeness date.
- 5 Check pre-approved plans
Many cities publish them. See our pre-approved ADU plans research.
What this page does not cover
This page covers the California statute only. It does not cover building codes, septic and well rules, HOA covenants, flood or wildfire overlays, or your city’s fee schedule. Those can still stop a project the statute allows.
We read the statute on October 27, 2026. Laws change, and courts read them.
If your project depends on one clause, have a land-use attorney or the planning department confirm it for your parcel.
For the national picture, see which states have ADU laws; for what to ask at the counter, see the ADU permit guide.
Questions
Can a California city ban ADUs?
Do I have to live on the property to build an ADU in California?
How big can an ADU be in California?
How long does a California city have to approve an ADU?
Are ADUs exempt from impact fees in California?
Written and audited by
HyreADU Research Desk
Primary-source research, data analysis and fact checking
We are a research desk, not a builder. We read the permit extract, the statute, the HCD return or the fee schedule ourselves, and publish each figure with its source and retrieval date.
Where a number cannot be traced to a primary source, we leave it out and say what we could not verify. Our store-based claims cover California only.
- CA
- the only state this desk will make store-based claims about
- 5
- jurisdictions with extracted ADU permit evidence
- 735
- CSLB-verified companies in the California store
- 0
- national claims from a one-state store
How this desk works
- Primary sources only. Permit counts come from the city or county that issued the permit. Production counts come from HCD’s Annual Progress Report. Rents come from HUD or the Census. We do not cite an article that cites a source; we download the source and compute the figure ourselves.
- This is a California site. The company store is 734 California firms and one New Mexico firm. Permit evidence exists for five named jurisdictions: Los Angeles, San Francisco, Sacramento, San José and unincorporated Marin. A number from that store is titled to those places, never to the United States.
- A permit is not a completion, and a license is not an ADU grade. California licenses no ADU classification. Being named on an ADU permit is evidence of engagement in that jurisdiction, not of quality, completion, or work anywhere else. Owner-builder permits are excluded from contractor counts.
- Calculation is labeled as calculation. Figures we derive are never presented as something HCD, HUD, the Census or a city published. Terner Center research is cited as Terner’s, never restated as ours.
- We do not design, permit or build ADUs, and we take no payment for placement, ranking or a favorable mention. Pages that look like rankings are not: they publish public-record counts and let the reader decide.
- Nothing here is legal, tax or financial advice. Zoning, underwriting and appraisal practice vary by jurisdiction, lender and appraiser. The useful next step on a specific lot is the planning counter and a licensed professional.
Data as of Gov. Code §§ 66314–66342 (via the HCD ADU Handbook, January 2025) read on the HCD ADU Handbook (January 2025 edition) hosted by the California State Assembly Housing Committee, retrieved 2026-10-27.. Authorship on this site is organizational: the analysis belongs to the desk rather than to a named individual, and we do not publish credentials we do not hold.
Our editorial policy sets out how we source, date and correct what we publish.
Sources & retrieval dates
- California Department of Housing and Community Development, Accessory Dwelling Unit Handbook (January 2025 update) , hosted by the Assembly Committee on Housing and Community Development; cites Gov. Code §§ 66314–66342 Retrieved October 27, 2026.
- California Government Code, Title 7, Chapter 13 (§§ 66310–66342) , leginfo.legislature.ca.gov returned HTTP 403 on the retrieval date, so section text was read through the HCD Handbook above Retrieved October 27, 2026.
Planning an ADU in California?
Tell us about your lot and what you want to build. Matching is not live yet, so this is not a quote. We will send ADU options and the next questions to ask your city.
HyreADU is a publisher. It does not design, permit or build ADUs, and matching with builders is not live yet. This page describes state statutory text as published on the retrieval date.
It is not legal advice. Your city or county applies the rules to your lot, and its planning department is the authority for your parcel.