The short answer: California ADU laws (Government Code §§ 66310–66342) override most local restrictions on accessory dwelling units. In 2026 it got faster and clearer: cities now have 15 business days to tell you whether your application is complete and 60 days to approve or deny it. On a typical single-family lot, the state guarantees you can combine a converted ADU, a Junior ADU (JADU) and an 800 sq ft detached ADU, with no owner-occupancy requirement for the ADU.
Last verified: October 2, 2026 · Written by the ADU Scope editorial team
| Rule | Statewide floor |
|---|---|
| Decision deadline | 60 days after a complete application; completeness check within 15 business days |
| Guaranteed detached ADU | 800 sq ft interior livable space, 4-ft side and rear setbacks, 16 ft tall |
| JADU | Up to 500 sq ft, inside your existing home |
| Impact fees | None for ADUs of 750 sq ft or less; proportional above that |
| Owner occupancy | Cannot be required for an ADU |
| Parking | Never required for conversions and JADUs; at most one space otherwise, with many exemptions |
California’s own count shows why cities take this seriously: ADU permits grew from 1,336 in 2016 to 30,354 in 2024, about 26.6% of all homes permitted statewide, according to the state housing department (HCD).
What changed in California ADU laws for 2026
Four 2025 laws reshaped the rules. AB 462 took effect on October 10, 2025. AB 1154, SB 9 and SB 543 took effect on January 1, 2026.
SB 543: faster, clearer permitting
- 15-business-day completeness check. Your city must tell you in writing whether your application is complete. If it misses that deadline, the application is deemed complete.
- No more vague rejections. An incomplete notice must list what is missing and how to fix it. You can appeal, and the city owes you a final written decision within 60 business days of the appeal.
- Size is measured as interior livable space. The state definition counts bedrooms, bathrooms, kitchens, laundry rooms, closets and interior stairs.
- Fee thresholds follow the same measure. No impact fees for an ADU of 750 sq ft or less or a JADU of 500 sq ft or less, and units under 500 sq ft are exempt from school fees.
- Combinations are spelled out. A converted ADU, a JADU and a detached ADU can go on the same lot.
AB 1154: JADU rules
A JADU now requires the owner to live on the property only if it shares a bathroom with the main house. JADUs can no longer be short-term rentals: any rental must be longer than 30 days.
SB 9 (2025): cities that skip the paperwork lose control
Not to be confused with the 2021 lot-split law of the same number. If a city fails to send a newly adopted ADU ordinance to HCD within 60 days, or ignores HCD’s findings for 30 days, that ordinance is void. Only state law applies until the city fixes it. The same applies to JADU ordinances.
AB 462: coastal zone
For ADUs in the coastal zone, the local agency must approve or deny the coastal development permit within 60 days of a complete application when there is an existing primary dwelling. State ADU law does not weaken Coastal Act resource protections, so coastal lots can still face extra review.
Earlier changes that still catch owners off guard
- No owner-occupancy requirement for ADUs (AB 976, 2024).
- Cities may allow selling an ADU as a condominium (AB 1033, 2024). It is optional for the city.
- Up to eight detached ADUs on a lot with an existing multifamily building, not exceeding the number of existing units.
- Unpermitted ADUs built before January 1, 2020 cannot be denied a permit over code violations, unless correcting them is needed to protect health and safety.
- Pre-approved plans: cities had to create a program for pre-approved ADU plans by January 1, 2025.
What California ADU laws let you build on a single-family lot
State law sets four types of units. The first three must be allowed together:
| Unit | Size limit | Height | Setbacks |
|---|---|---|---|
| Converted ADU (inside your home, garage or shed) | No state size cap; you can add up to 150 sq ft to a converted accessory structure for entrances and stairs | Existing structure | None required, but it needs exterior access and fire-safety clearance |
| JADU (inside the walls of the home, attached garage included) | 500 sq ft | Existing structure | None |
| New detached ADU | 800 sq ft interior livable space | 16 ft; 18 ft near major transit; up to 2 extra feet to match the roof pitch | 4 ft side and rear; it may sit in the front setback if nothing else fits |
| Additional ADU under the local ordinance (attached or detached) | A city cap cannot go below 850 sq ft (studio or 1-bedroom) or 1,000 sq ft (2+ bedrooms). State-law ceilings for these units (Gov. Code section 66314): up to 1,200 sq ft detached, or up to 50% of the primary dwelling if attached | Detached 16–18 ft; attached 25 ft or the local limit if lower | 4 ft side and rear |
HCD’s handbook says cities must allow at least one ADU from the fourth row in addition to the three state-mandated units. In practice, whether your lot physically fits all of them, and how your city applies this, varies. Check with your planning department before you design.
Cities cannot impose lot-size minimums, and they cannot use lot coverage, floor-area ratio, open-space or front-setback rules to block an 800 sq ft ADU with 4-ft side and rear setbacks. They also cannot cap the number of bedrooms.
Multifamily lots
An apartment building can convert non-livable space (storage, garages, boiler rooms) into at least one ADU, up to 25% of existing units. It can also add up to eight detached ADUs on an existing building, or two on a proposed one. JADUs are not allowed on multifamily lots.
Rules in California ADU laws that apply to nearly every ADU
- Approval. Review is ministerial: no hearing and no discretionary judgment. A denial must come with a full list of defects and how to fix them.
- Fees. Zero impact fees up to 750 sq ft. Above that, fees are proportional (a 2026 law, SB 1117, will change this to charge only the area above 750 sq ft for lots with up to two ADUs, expected from January 1, 2027): HCD’s example is a 1,000 sq ft ADU behind a 2,000 sq ft house paying up to half the fee for a new house. Conversions and JADUs cannot be treated as new homes for water and sewer connection fees, unless they are built with a new house.
- Parking. At most one space per ADU or per bedroom, whichever is fewer. Cities cannot require parking for conversions, JADUs, or ADUs within half a mile of public transit. They also cannot require you to replace the garage or carport you demolish or convert.
- Owner occupancy and rentals. None for ADUs. Cities may require rental terms of 30 days or longer for ADUs under their own ordinance.
- HOAs. Covenants that effectively prohibit or unreasonably restrict an ADU are void. An HOA cannot influence the city’s approval or charge fees as a condition.
- Utilities. A conversion or JADU cannot be forced to get a separate utility connection. Other ADUs can be.
- Fire sprinklers and solar. Sprinklers are required only if the main house needs them. New detached ADUs must meet the state Energy Code solar requirement. An existing system does not count: new panels must be part of the ADU permit and sit on the same lot, and they can serve either the ADU or the main house.
What your city can still control under California ADU laws
- Objective design standards, such as colors, materials and landscaping on new-construction ADUs. Subjective standards like “neighborhood compatibility” are not allowed.
- Building and fire codes. Every ADU must meet the dwelling building code.
- Permit and plan-check fees, which vary widely by city.
- Special areas: the coastal zone, the Lake Tahoe basin (which follows its own regional agency) and mobilehome parks, where ADUs are not allowed.
How to check which California ADU laws apply to your lot
- Find your city’s ADU page and ordinance. If the city never adopted one, only state law applies.
- Check whether your lot is within a half mile of transit. The state’s geoportal has a map for the 18-ft height allowance.
- Look for your city’s pre-approved ADU plans, which speed up review.
- Call or visit planning before you design. Ask which unit types they will approve on your lot.
- If your city seems to violate state law, first use its appeal process, then HCD’s online ADU portal. HCD helps mainly when an application is pending.
FAQ
Do I have to live on the property?
Not for an ADU. For a JADU, only if it shares a bathroom with the house.
Can I use it as an Airbnb?
Cities may require rental terms of 30 days or longer for ADUs under their own ordinance, and the state requires terms longer than 30 days for JADUs and state-mandated (section 66323) units. Check your local ordinance.
Can I sell the ADU separately?
Only if your city adopted a condominium ordinance under AB 1033, or in a narrow nonprofit-built exception.
Can my HOA stop me?
Not if its rules effectively prohibit ADUs. Report it to your city.
Is there state grant money?
HCD’s handbook says the CalHFA ADU grant funds were exhausted at the time of writing. Check your city and county for local programs.
Next steps
- How Much Does an ADU Cost in California? 2026 Prices by Type, Size and Per Square Foot
- Garage Conversion to ADU in California: Permits, Parking and Conversion vs. New Detached ADU
- Pre-Approved ADU Plans: Which Cities Offer Them and What They Cost
- How Long Does It Take to Get an ADU Permit in California?
- ADU Setback Requirements Explained: California, Washington, Colorado and Portland
- Unpermitted ADU in California: How to Legalize It Under AB 2533
General information, not legal advice. Local rules vary and change; confirm with your planning department.
Sources: HCD ADU Handbook, March 2026 (PDF) · HCD ADU Handbook page · California Legislative Information