Starting January 1, 2027, your city must approve two backyard ADUs on a single-family lot, and more HOA bans become void. Here's what changes and how to plan.
The short answer
Yes. Starting January 1, 2027, California law (AB 956) requires your city to approve two new detached ADUs on a lot with a single-family home, without a hearing. Today the state guarantees only one. The same law also stretches HOA protections to more lots.
new detached ADUs your city must approve per single-family lot (Gov. Code § 66323)
when AB 956 takes effect (Chapter 791, Statutes of 2026)
the smallest size cap a city may put on each unit
the most a city can require from side and rear lot lines
For years, California homeowners got the same answer at the planning counter: one backyard cottage, plus maybe a small unit carved out of the house. Want a second cottage? That depended on your city.
On September 29, 2026, Governor Newsom signed Assembly Bill 956, by Assemblymember Sharon Quirk-Silva. It moves that line. From January 1, 2027, a second detached ADU stops being a favor and becomes a right. For a homeowner, that can mean two rent checks from one backyard. Here's what changes, what doesn't, and the one trade-off to know before you draw anything.
What does AB 956 change?
It raises the number of new detached ADUs your city must approve "ministerially" (by checklist, no hearing, no neighbor vote) from one to two on any lot with an existing or planned single-family home.
The rule lives in Government Code § 66323, the part of state law that lists ADU combinations a city can't refuse. Before AB 956, it read "one detached, new construction, accessory dwelling unit." The chaptered text now reads "two detached, new construction, accessory dwelling units that do not exceed four-foot side and rear yard setbacks."
| On a single-family lot | Through Dec. 31, 2026 | From Jan. 1, 2027 |
|---|---|---|
| New detached ADUs the city must approve | 1 | 2 |
| ADU or JADU inside the house or an existing structure | Yes, one of each | Yes, one of each |
| JADU when two detached ADUs are built | Not applicable | City may say no |
| HOA ban protection | Lots zoned single-family | Lots zoned to allow single-family |
Source: AB 956 chaptered text, Gov. Code § 66323 and Civ. Code §§ 714.3, 4751, checked October 8, 2026.
Your city's website may lag
Many city ADU pages will still say "one detached ADU" in January. That's normal. State law sets the floor, and a city can be more generous, not stricter. If the page and the statute disagree, ask the planner which rule they apply.
How big can each of the two ADUs be?
Your city may cap each detached unit at 800 sq ft of livable space and apply the state height limits. It can't add other design rules to these units.
A city may limit each unit to 800 sq ft of livable space, but not less.
Gov. Code § 66323(a)(2)(A)At least 16 feet; 18 feet near major transit, plus 2 feet to match your roof pitch.
Gov. Code § 66321(b)(4)No more than 4 feet from side and rear lot lines.
Gov. Code § 66323(a)(2)The city can't impose design standards the section doesn't authorize.
Gov. Code § 66323(c)Two 800 sq ft units add up to 1,600 sq ft of new living space. Every one of our factory-built models fits under that cap: the 2 Bedroom ADU is 640 sq ft and the 1 Bedroom is 480 sq ft. On a tight lot, a 320 sq ft studio plus a one-bedroom can fit where two large units can't.
Can I still add a junior ADU if I build two?
Not guaranteed. Once two detached ADUs are built under this rule, your city doesn't have to approve a junior ADU (JADU) on the same lot.
A JADU is a unit of up to 500 sq ft inside your house, often a converted bedroom. The new § 66323(b) lets a city decline one when you already have two detached units. It may still approve it, so ask.
Plan the whole lot at once
If you want a JADU for a parent and two rentals out back, sketch all three before you apply. The order in which you build can decide what your city must approve.
Can my HOA still block an ADU?
No, and from 2027 on more lots are protected. HOA rules that ban or unreasonably restrict an ADU become void on any lot "zoned to allow" a single-family home, not just lots zoned single-family.
The difference matters for homes in planned developments or in multifamily and mixed-use zones that also allow houses. Under today's wording, an owner there could get stuck arguing whether the protection applies. AB 956 rewrites Civil Code § 4751 (HOAs and planned developments) and § 714.3 (deeds and other recorded restrictions) to close that gap.
An HOA may still set "reasonable restrictions," meaning rules that don't unreasonably raise your cost or effectively stop the build. Since 2025, § 714.3 also says those restrictions can't include fees or other financial requirements.
Will two ADUs mean two sets of fees?
Each ADU is judged on its own size. Keep each one at 750 sq ft or less, and state law bars local impact fees on both (Gov. Code § 66311.5). School districts may still charge a fee on units over 500 sq ft.
Above 750 sq ft, a second law signed the same day, SB 1117, limits impact fees to the footage over 750 for up to two ADUs, starting January 1, 2027. Permit and plan-check fees still apply to each unit. Your city's fee schedule has the exact numbers; our ADU cost guide shows what's usually in an all-in price.
One rule doesn't change: units approved under § 66323 must be rented for more than 30 days at a time. Two ADUs means two long-term leases, not two Airbnbs. To run the numbers, try our rental and ROI calculator.
When should I apply for two ADUs?
AB 956 has no urgency clause, so it takes effect January 1, 2027. If your plan depends on the second detached unit, submit the permit application in 2027 and confirm with your planning department.
You don't need to wait to plan, though. Checking the lot, picking models, and drawing the site plan all take time. Start now, and your application can be ready on day one.
Check the lot
We review satellite imagery, mark the buildable area and delivery access, and check your city's ADU rules.
Apply in January
Your city has 60 days to approve or deny a complete application (Gov. Code § 66317).
Does your lot fit two ADUs?
We'll check the buildable area, access for delivery, and your city's rules. Free, no obligation.
Frequently asked questions
Can I build two ADUs on my lot in California?
From January 1, 2027, yes: AB 956 requires cities to approve two new detached ADUs on a lot with a single-family home, with 4-foot side and rear setbacks. Until then, state law guarantees one.
When does AB 956 take effect?
January 1, 2027. The governor signed it on September 29, 2026 (Chapter 791, Statutes of 2026), and it has no urgency clause.
Can my city limit the size of the two ADUs?
Yes, to no less than 800 sq ft of livable space each, plus the state height limits of 16 to 18 feet. It can't add other design standards.
Can I have two detached ADUs and a JADU?
Your city may approve it but doesn't have to. AB 956 lets a city decline a JADU on a lot where two detached ADUs were built under this rule.
Can I rent both ADUs on Airbnb?
No. Units approved under Gov. Code § 66323 must be rented for terms longer than 30 days.
Does AB 956 apply to factory-built ADUs?
Yes. The law covers the unit, not the building method. The state oversees the factory build; your city inspects the foundation and hookups. See what factory-built housing is.
Find out if your backyard fits two
We'll review your lot and your city's ADU rules, then show which pair of models fits and their all-in prices. Free, no obligation.
About Bay Modular Team
Bay Modular is a California factory-built housing manufacturer (HCD #1585366). We design and build backyard ADUs in our factory in Lathrop, CA, and install them across California. More about us
Sources
- California Legislature, AB 956 (Quirk-Silva), Chapter 791, Statutes of 2026, approved by the Governor September 29, 2026. Accessed October 8, 2026.
- California Legislature, SB 1117 (Chapter 809, Statutes of 2026). Accessed October 8, 2026.
- Gov. Code § 66311.5, § 66317, § 66321, § 66323; Civ. Code § 714.3, § 4751. Accessed October 8, 2026.
- California Department of Housing and Community Development (HCD), Accessory Dwelling Unit Handbook, March 2026.
- California Constitution, Article IV, Section 8(c) (effective date of statutes).
This article is general information, not legal advice. AB 956 takes effect January 1, 2027, and cities may update their ordinances on their own schedule; confirm details with your city's planning department before you design or apply.
