Informational only, not legal advice. ADU rules change often and differ by city. Confirm with your local planning department before you rely on anything here.
AB 956, by Assemblymember Sharon Quirk-Silva, was approved by Governor Newsom and chaptered on September 29, 2026 (Chapter 791, Statutes of 2026). Starting January 1, 2027, every California city and county must ministerially approve two detached, new-construction ADUs on a lot with an existing or proposed single-family home, up from one. It is the biggest change to the single-family ADU count since the state first guaranteed an ADU on every residential lot in 2016.
From January 1, 2027, a typical single-family lot can hold the house plus two new detached backyard units of up to 800 square feet each, with four-foot side and rear setbacks, approved without a hearing. The trade-off: if you build both detached units, the city no longer has to approve a JADU. If you are designing now for a 2027 permit, plan the backyard for two cottages, not one.
What AB 956 changes in Government Code 66323
Section 66323 is the short list of ADU combinations a city must approve no matter what its local ordinance says. Before AB 956, paragraph (a)(2) guaranteed one detached, new-construction ADU on a single-family lot. AB 956 rewrites it to read "two detached, new construction, accessory dwelling units" on a lot with a proposed or existing single-family dwelling.
The conditions a city can attach to each unit did not change:
- Size: the city may cap each unit at 800 square feet of livable space, and no lower.
- Setbacks: side and rear setbacks of no more than four feet.
- Height: the state ADU height limits in Section 66321(b)(4) — generally 16 feet, rising to 18 feet near major transit or on a lot with a multistory multifamily building, plus two feet to match the roof pitch of the main house.
The bill also says a city cannot apply any objective development or design standard to these units that Section 66323 does not authorize. That matters: lot coverage, floor-area ratio, open-space and minimum lot size rules cannot be used to knock the second unit off the lot.
How many ADUs can I build on a single-family lot in 2027?
Read with the combination language added to Section 66323 in 2025, the state floor for a single-family lot becomes one of two configurations. Both total three accessory units plus the house:
| Configuration | Converted ADU | JADU | New detached ADUs |
|---|---|---|---|
| A (today's maximum, still allowed) | 1 | 1 | 1 |
| B (new under AB 956) | 1 | Not guaranteed | 2 |
The JADU carve-out is the one real compromise in the bill. The Senate floor analysis describes it as keeping the single-family lot consistent with the four-unit ceiling that SB 9 effectively sets. In practice we expect most owners to prefer configuration B: two detached units rent as true standalone homes, while a JADU shares a wall with you and tops out at 500 square feet. If you already have a JADU, nothing in the bill takes it away. Cities are also free to allow more than the state floor; many already do.
For the current rules, see our guide to the two-ADU rule and the full California ADU laws 2026 roundup. The details of the detached unit itself — setbacks, height and cost — are in our detached ADU guide.
HOAs and private covenants
AB 956 also amends Civil Code sections 714.3 and 4751, the statutes that void CC&Rs which "effectively prohibit" or "unreasonably restrict" an ADU. Those protections used to apply to lots zoned for single-family use. They now apply to lots zoned to allow single-family use, which reaches multifamily and mixed-use zones where a single house is the primary use. Section 4751 now refers to planned developments specifically. Reasonable restrictions are still allowed, and these are disputes between owners and associations, not something the city enforces.
What cities have to do before January 1
State ADU law has a hard backstop: a local ordinance that conflicts with it is void, and the state standards apply until the city fixes it. So on January 1, 2027, a city whose code still says "one detached ADU" cannot use that line to deny a second unit. Expect a wave of ordinance amendments in November and December, and expect HCD to review them under its ADU enforcement authority. Plan checkers will take a few months to catch up, so bring a copy of the statute to your pre-application meeting.
How it fits with SB 9, SB 1211 and Parcy
AB 956 only changes single-family lots. Multifamily lots stay under SB 1211: up to eight detached ADUs on a lot with existing apartments, capped at the number of existing units. If you plan to split the lot under SB 9, remember that a city does not have to allow ADUs on lots that use both the SB 9 lot split and the SB 9 duplex, so compare a lot split against two detached ADUs before choosing a path — for many owners who want to keep the property and rent the units, two ADUs is the simpler, cheaper permit.
The economics also improve in 2027 because of a companion bill, SB 1117, which cuts impact fees on ADUs over 750 square feet for lots with up to two ADUs. Two units under 750 square feet pay no impact fees at all.
Our recommendation: if your lot is deep enough for two 800-square-foot footprints with four-foot setbacks, design for both now and file after January 1, 2027. If your city's ordinance already allows two, you do not have to wait. Parcy draws the buildable area for both units on your parcel, so you can see whether the second cottage fits before paying an architect.
Frequently asked questions
Can I build two detached ADUs on a single-family lot in California?
Yes, starting January 1, 2027. AB 956 requires cities to ministerially approve two detached, new-construction ADUs on a lot with an existing or proposed single-family home.
How big can each ADU be under AB 956?
A city may cap each of the two by-right detached ADUs at 800 square feet of livable space, require side and rear setbacks of up to four feet, and apply the state ADU height limits. Many cities allow larger units under their own ordinances.
Can I still add a JADU if I build two detached ADUs?
Not as a matter of right. AB 956 says a city does not have to approve a JADU on a lot where two detached, new-construction ADUs have been built. You can still pair a converted ADU with the two detached units.
Can my HOA stop me from building two ADUs?
An HOA cannot effectively prohibit or unreasonably restrict an ADU on a lot zoned to allow single-family use. AB 956 extends that protection to zones that allow single-family homes even if they are not exclusively single-family.
When does AB 956 take effect?
January 1, 2027. Governor Newsom approved it and it was chaptered on September 29, 2026 as Chapter 791, Statutes of 2026.
Official bill text
- AB 956 — Accessory dwelling units and junior accessory dwelling units. (official bill text, California Legislative Information)
Sources
- AB 956 (2025-26): bill status, chaptered text and Senate floor analysis — Chaptered September 29, 2026, Chapter 791, Statutes of 2026; amends Gov. Code 66323 and Civil Code 714.3 and 4751
- Best Best & Krieger: California further expands state ADU law (October 2026) — Section 66323 combinations and HOA covenant changes
- HCD: Accessory Dwelling Units — State ADU handbook and enforcement
- AB 956
- two detached ADUs
- two detached ADUs California
- AB 956 ADU law 2027
- how many ADUs can I build on a single-family lot
- 800 square foot ADU
- ADU HOA rules California
- California ADU
Stay ahead of the next ADU bill.
New California housing bills, what they mean for your lot, and news from Parcy and Kaz Capital Group. A few emails a month.
Informational only. Not legal, architectural, or investment advice. Confirm current rules with your local planning department.