AB 956, signed by Governor Newsom on September 29, 2026, lets California homeowners build up to two detached, new-construction ADUs on a lot zoned for single-family use, up from one. Qualifying projects get ministerial approval, with no public hearing. The law takes effect January 1, 2027.
There’s a trade-off: a city isn’t required to also approve a Junior ADU on a lot that has two detached ADUs. Here’s what the law does and doesn’t do.
What does AB 956 change?
Before AB 956, state law guaranteed one detached, new-construction ADU on a single-family lot, which could be combined with a converted ADU and a Junior ADU. AB 956 raises the detached new-construction allowance from one to two.
Key points, based on published summaries of the bill:
- Two detached ADUs on a lot zoned for single-family residential use
- Ministerial approval: reviewed against objective standards, with no public hearing
- Size: a city may limit each detached ADU to 800 sq ft of livable space
- Setbacks: 4-foot side and rear setbacks continue to apply, along with state height limits
- JADU trade-off: a city isn’t required to approve a JADU on a lot with two detached ADUs
- HOAs: expands state protections against HOA rules that block ADUs
- Effective date: January 1, 2027
What doesn’t AB 956 do?
- It doesn’t waive building codes, fire rules, or height limits.
- It doesn’t create utility capacity. Two units need water, sewer or septic, and electrical service.
- It doesn’t take effect until January 1, 2027.
- It doesn’t settle every detail. Cities will update ordinances, and state guidance may follow.
What is SB 1117?
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. That matters if you’re planning two units in the 750 to 800 sq ft range.
What does this mean in Santa Clarita?
The City of Santa Clarita updated its ADU rules in April 2026, before AB 956 was signed. Expect the city, and LA County for unincorporated areas like Stevenson Ranch and Castaic, to address the new law. Until then, ask the Planning Division how it will handle two-detached-ADU applications in 2027.
Practical considerations:
- Lot size: two detached units, setbacks, access paths, and separation from the main house need real space. Sketch it before assuming it fits.
- Utilities: two units can trigger a panel upgrade, sewer work, or a larger water meter.
- Septic lots: in Acton and Agua Dulce, septic capacity may limit you to fewer units than the law allows. See ADUs on septic and well.
- Phasing: you can build one detached ADU now under current law and plan the second for 2027 or later.
Should you wait until 2027?
If you only want one ADU, there’s no need to wait. Current law already allows it. If you want two detached ADUs, you could design now and apply once the law takes effect and your city’s process is clear. Talk timing through with a contractor who follows local implementation.
Want to know if two ADUs fit your lot?
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.
AB 956 FAQs
When does AB 956 take effect?
January 1, 2027.
Can I have two detached ADUs and a Junior ADU?
Not as a guaranteed right. AB 956 says a city isn’t required to approve a JADU on a lot with two detached ADUs. A city could choose to allow more.
How big can each detached ADU be under AB 956?
A city may limit each one to 800 sq ft of livable space. Check your city’s ordinance for the limit it adopts.
Does AB 956 apply to multifamily lots?
AB 956 is aimed at lots zoned for single-family use. Multifamily lots already have separate rules, including up to 8 detached ADUs under SB 1211, capped at the number of existing units.