California law sets the floor for ADU rules, and cities must follow it. Cities have to allow ADUs within state size limits, can’t require more than 4-foot side and rear setbacks, can’t require owner-occupancy for an ADU, and must act on a complete application within 60 days. Two new laws signed in September 2026, AB 956 and SB 1117, take effect January 1, 2027.
This guide covers where the rules stand in late 2026 and how they apply in the Santa Clarita Valley. It’s general information, not legal advice.
What are the core state ADU rules?
| Rule | What state law says |
|---|---|
| Size | Cities can’t set a maximum below 850 sq ft for a studio or 1-bedroom ADU, or 1,000 sq ft for 2+ bedrooms |
| Guaranteed minimum | A city must allow at least an 800 sq ft ADU with 4-foot side and rear setbacks, even if lot coverage or floor-area limits would block it |
| Junior ADU | Up to 500 sq ft within the walls of a single-family home |
| Setbacks | No more than 4 feet from side and rear lot lines; none for a converted existing structure |
| Height | 16 feet for most detached ADUs, 18 feet near major transit or on some multifamily lots (plus 2 feet for roof pitch), and up to 25 feet for attached ADUs |
| Parking | No new parking in many cases, and no replacement parking when a garage is converted |
| Owner-occupancy | Not allowed as a requirement for ADUs |
| Impact fees | None on ADUs of 750 sq ft or less |
| Permit timing | 15 business days to confirm completeness, 60 days to approve or deny a complete application |
| Short-term rentals | ADUs and JADUs must be rented for terms longer than 30 days |
Which recent laws matter most?
- AB 68 and AB 881 (effective 2020): the big rewrite that limited local barriers on size, setbacks, parking, and approval times.
- SB 9 (2021): allows lot splits and two-unit projects on many single-family lots.
- AB 2221 and SB 897 (2022): clarified height limits and other ADU standards.
- AB 976 (2023): made the ban on owner-occupancy requirements for ADUs permanent.
- AB 2533 (2024): created a path to legalize ADUs built without permits before 2020.
- SB 1211 (2024): allows up to 8 detached ADUs on multifamily lots, capped at the number of existing units.
- SB 543 (effective 2026): measures size by interior livable space, confirms that ADU types can be combined on one lot, and requires a completeness decision within 15 business days.
- AB 1154 (effective 2026): removes owner-occupancy for a Junior ADU that has its own bathroom and bars rentals of 30 days or less.
What changes in 2027?
AB 956 was signed September 29, 2026 and takes effect January 1, 2027. It allows up to two detached, new-construction ADUs on a lot zoned for single-family use, with ministerial approval. A city may cap each at 800 sq ft. A city isn’t required to also approve a Junior ADU on a lot with two detached ADUs. See AB 956 explained.
SB 1117 was signed the same day and also takes effect January 1, 2027. For the first two ADUs on a lot, impact fees can be charged only on the interior livable space above 750 sq ft.
How do these rules apply in Santa Clarita?
The City of Santa Clarita updated its ADU rules in April 2026. Its current ADU handout says:
- You may have each type of ADU on your property.
- There are no parking requirements for ADUs or JADUs.
- An ADU can’t be rented for less than 30 days and can’t be sold separately from the home.
- The main home or the JADU must be owner-occupied if they share sanitation facilities.
Areas outside city limits, such as Stevenson Ranch, Castaic, Acton, and Agua Dulce, follow LA County’s ADU ordinance. State law applies in both places, but offices, forms, and local details differ. See Santa Clarita ADU size, setback, height, and parking rules.
What can cities and HOAs still control?
Cities can still apply objective design standards, building and fire codes, and utility requirements. HOAs can apply reasonable architectural rules, but California Civil Code 4751 voids HOA rules that effectively prohibit or unreasonably restrict an ADU. See HOAs and ADUs.
Want someone to check your lot against the current rules?
Call (661) 486-8393. If no one answers, leave a voicemail with your name, phone number, address, and the type of ADU you want. You can also use the contact form. We’ll pass your details to a local ADU contractor, who will follow up with you directly. There’s no obligation to hire.
California ADU law FAQs
Do I have to live on the property if I build an ADU?
No. State law bars owner-occupancy requirements for ADUs. A Junior ADU that shares a bathroom with the main house still requires the owner to live in the house or the JADU.
Can I rent my ADU on Airbnb?
Not for short stays. State law now requires ADU and JADU rentals to be longer than 30 days, and the City of Santa Clarita’s handout says the same.
Can I build two detached ADUs now?
Not under the new path until January 1, 2027, when AB 956 takes effect. Projects decided before then follow current law.
Can a city deny my ADU for lot coverage?
Not if it’s an ADU of up to 800 sq ft that meets 4-foot side and rear setbacks and the height limit. State law guarantees that size regardless of lot coverage or floor-area limits.
Can I legalize an unpermitted ADU?
Possibly. AB 2533 limits when a city can deny a permit for an unpermitted ADU built before 2020. Health and safety issues still have to be fixed.
Sources
- City of Santa Clarita Planning Division: ADU handout (2026)
- The Signal: City adopts new ADU rules (April 2026)
- Best Best & Krieger: Governor signs four new ADU bills (SB 543, AB 1154)
- LA County Planning: SB 543 and AB 1154 memo
- California YIMBY: AB 956
- LA Construction Compliance: AB 956 signed, effective January 1, 2027
- LegiScan: SB 1117 (chaptered September 29, 2026)
- California Government Code 66321 (ADU size and height)
- California Civil Code 4751 (HOAs and ADUs)