AB 956 (Quirk-Silva), Chapter 791, Statutes of 2026, takes effect January 1, 2027. It requires every California city to approve two detached, new-construction ADUs by right on a lot with a single-family home, up from one. A city may cap each at 800 square feet of livable space.
Last verified: October 22, 2026 against the chaptered text and status page of AB 956 (Chapter 791, Statutes of 2026) and the current Government Code Section 66323 at leginfo.legislature.ca.gov, read through a page parser because the site blocks direct reads from our build environment.
AB 956 in One Paragraph
AB 956 is Assembly Bill 956 of the 2025-2026 session, by Assemblymember Quirk-Silva. The Governor approved it on September 29, 2026, and it was chaptered the same day as Chapter 791, Statutes of 2026. It has no urgency clause, so it takes effect January 1, 2027. The headline change is one word in Government Code Section 66323(a)(2): the number of detached, new-construction ADUs a city must approve ministerially on a single-family lot goes from “One” to “Two.” Ministerial means the city checks your plans against objective rules and approves them, with no hearing and no discretion.
What AB 956 Actually Says
AB 956 amends three sections. Here is each change, in plain language, with the section in parentheses.
| Provision | What it says | Section |
|---|---|---|
| Two detached ADUs | A city must ministerially approve two detached, new-construction ADUs on a lot with a proposed or existing single-family home, with side and rear setbacks of no more than four feet | Gov. Code 66323(a)(2) |
| Size cap a city may impose | Each detached unit may be limited to “not more than 800 square feet of livable space” | Gov. Code 66323(a)(2)(A) |
| Height a city may impose | The state height tiers in Section 66321(b)(4)(A) to (C), for example 16 feet for a detached ADU on a single-family lot | Gov. Code 66323(a)(2)(B) |
| JADU trade-off | A city does not have to ministerially approve a junior ADU on a lot where two detached ADUs were built under (a)(2) | Gov. Code 66323(b) (new) |
| HOA rules | A covenant or HOA rule that effectively prohibits or unreasonably restricts an ADU is void on a lot “zoned to allow single-family residential use,” not only a lot zoned single-family | Civil Code 4751 |
| Deed restrictions | The same widening for any recorded instrument affecting a sale or transfer | Civil Code 714.3 |
Two things did not change. The conversion path in Section 66323(a)(1), one ADU and one JADU inside the existing or proposed house or an accessory structure, reads the same. And the multifamily counts in Section 66323(a)(3) and (a)(4), which SB 1211 set, are untouched.
How Many ADUs Can You Have in California in 2027?
Yes, from January 1, 2027. AB 956 requires California cities to approve two detached, new-construction ADUs by right on a lot with a single-family home, each up to 800 square feet with four-foot side and rear setbacks. Through 2026 the state guarantee was one.
Here is the state floor on a single-family lot, before and after. These are guarantees under Section 66323, the ministerial path. Your city’s own ordinance can always allow more.
| On a single-family lot | Through December 31, 2026 | From January 1, 2027 | Section |
|---|---|---|---|
| Detached, new-construction ADUs | One | Two | 66323(a)(2) |
| Size a city may cap each detached ADU at | 800 sq ft of livable space | 800 sq ft of livable space, each | 66323(a)(2)(A) |
| Side and rear setbacks | No more than 4 feet | No more than 4 feet | 66323(a)(2) |
| ADU or JADU converted from existing space | One ADU and one JADU | One ADU and one JADU | 66323(a)(1) |
| JADU when two detached ADUs are built | Not applicable | City not required to approve it | 66323(b) |
Can You Build Three Detached ADUs?
Builder blogs are already pitching three detached units: two under Section 66323 plus a third under your city’s general ADU rules in Section 66314. That depends on your city’s ordinance and your lot. AB 956 guarantees two. A third detached unit is a local-standards question, and cities can still apply lot coverage, setbacks and other objective rules to it.
There is a second route people ask about. The lead-in to Section 66323(a) lets you combine “any of the following units, or any combination.” Read on its face, a converted ADU under (a)(1) plus two detached units under (a)(2) is a combination. HCD has not published 2027 guidance on that combination as of October 22, 2026, so treat it as a question for your planning department, not a promise.
Does AB 956 Apply to Your Lot?
Work down this list. If you answer yes to the first three, AB 956 covers you from January 1, 2027.
- Is the lot in a residential or mixed-use zone? Section 66323(a) applies there. If not, AB 956 does not reach it.
- Is there a single-family home on it, existing or proposed? The two-unit rule is for “a lot with a proposed or existing single-family dwelling.” A vacant lot qualifies only once a house is proposed with it.
- Are both ADUs new, detached construction? Converting a garage or adding onto the house is the (a)(1) path, not this one.
- Is the lot a duplex or apartment lot? Then the multifamily counts apply instead. See SB 1211.
- Are you in an HOA? Read the HOA section below. The HOA cannot ban the units, but it can impose reasonable rules.
- Do you already have a JADU, or want one? Read the JADU trade-off next.
Outcome: yes on zone, house and new detached construction means a city must approve two qualifying units ministerially from January 1, 2027. Anything else, check with your city.
The JADU Trade-Off
AB 956 adds a new Section 66323(b): a city “is not required to ministerially approve an application for a building permit to create a junior accessory dwelling unit on the same lot where two detached, new construction, accessory dwelling units have been constructed.” In plain terms, the state guarantee becomes two detached ADUs, or one detached ADU plus the ADU and JADU combination, but not every unit at once.
Two details matter. First, the trigger is two detached units “constructed” under (a)(2), so the order you build in can matter; ask your city how it reads that before you sequence a project. Second, “not required” is not “prohibited.” A city can still allow the JADU under its own ordinance. Our junior ADU guide covers what a JADU is and what it costs.
Can Your HOA Stop a Second ADU?
No, not outright. Civil Code Section 4751 voids any HOA governing document that “effectively prohibits or unreasonably restricts” an ADU or JADU, and Civil Code Section 714.3 does the same for deed restrictions. Before AB 956, both protected lots “zoned for single-family residential use.” From January 1, 2027, both protect lots “zoned to allow single-family residential use,” which pulls in lots in zones that allow single-family homes alongside other housing.
An HOA can still impose “reasonable restrictions”: rules that do not unreasonably raise the cost, effectively prohibit the unit, or extinguish your ability to build it. Design review, materials and placement rules usually live here. Honestly, the fight is rarely over whether you can build. It is over what the HOA calls reasonable, so get its architectural rules in writing before you pay for plans.
How California Cities Are Applying AB 956
This is the table nobody else has built. We checked each city we cover, plus the places people search for most, on October 22, 2026. No city or county had published AB 956 guidance yet, which is normal for a law that takes effect in January. Where a city has not updated its ordinance, state law applies from January 1, 2027, and a local rule that conflicts with it gives way. We will update each row as cities publish.
| City / County | Status | Local program or form | Key local difference | Fee or timeline | Source | Our guide |
|---|---|---|---|---|---|---|
| Los Angeles | No AB 956 guidance found as of Oct 22, 2026; state law applies from Jan 1, 2027 | None yet | LA runs ADUs under ZA Memo 143 Revision 1, which predates AB 956 | Not published | Web search, Oct 22, 2026; no city page located | Los Angeles ADU permits |
| San Jose | No AB 956 guidance found as of Oct 22, 2026; state law applies from Jan 1, 2027 | None yet | City standards already allow a detached ADU up to 1,000 sq ft (lot under 9,000 sq ft) or 1,200 sq ft | Not published | Web search, Oct 22, 2026; no city page located | San Jose ADU permits |
| Sunnyvale | No AB 956 guidance found as of Oct 22, 2026; state law applies from Jan 1, 2027 | None yet | Planning Miscellaneous Plan Permit for new ADUs over 800 sq ft | Not published | Web search, Oct 22, 2026; no city page located | Sunnyvale ADU permits |
| Berkeley | No AB 956 guidance found as of Oct 22, 2026; state law applies from Jan 1, 2027 | None yet | None published | Not published | Web search, Oct 22, 2026; no city page located | Berkeley ADU permits |
| Long Beach | No AB 956 guidance found as of Oct 22, 2026; state law applies from Jan 1, 2027 | None yet | None published | Not published | Web search, Oct 22, 2026; no city page located | Long Beach ADU permits |
| Los Altos | No AB 956 guidance found as of Oct 22, 2026; state law applies from Jan 1, 2027 | None yet | City-owned pre-approved detached plans in three sizes | Not published | Web search, Oct 22, 2026; no city page located | Los Altos ADU permits |
| Los Gatos | No AB 956 guidance found as of Oct 22, 2026; state law applies from Jan 1, 2027 | None yet | ADU ordinance update already in progress | Not published | Web search, Oct 22, 2026; no city page located | Los Gatos ADU permits |
| Campbell | No AB 956 guidance found as of Oct 22, 2026; state law applies from Jan 1, 2027 | None yet | $9,328 park in-lieu fee on an ADU of 750 sq ft and up (FY 2026-27) | Not published | Web search, Oct 22, 2026; no city page located | Campbell ADU permits |
| Santa Clara | No AB 956 guidance found as of Oct 22, 2026; state law applies from Jan 1, 2027 | None yet | $306 flat Architectural Review / ADU fee | Not published | Web search, Oct 22, 2026; no city page located | Santa Clara ADU permits |
| Cupertino | No AB 956 guidance found as of Oct 22, 2026; state law applies from Jan 1, 2027 | None yet | None published | Not published | Web search, Oct 22, 2026; no city page located | Cupertino ADU permits |
| Saratoga | No AB 956 guidance found as of Oct 22, 2026; state law applies from Jan 1, 2027 | None yet | None published | Not published | Web search, Oct 22, 2026; no city page located | Saratoga ADU permits |
| Riverside | No AB 956 guidance found as of Oct 22, 2026; state law applies from Jan 1, 2027 | None yet | None published | Not published | Web search, Oct 22, 2026; no city page located | Riverside ADU permits |
| San Diego | No AB 956 guidance found as of Oct 22, 2026; state law applies from Jan 1, 2027 | None yet | None published | Not published | Web search, Oct 22, 2026; no city page located | San Diego ADU costs |
| San Francisco | No AB 956 guidance found as of Oct 22, 2026; state law applies from Jan 1, 2027 | None yet | None published | Not published | Web search, Oct 22, 2026; no city page located | San Francisco ADU costs |
| Orange County (unincorporated) | No AB 956 guidance found as of Oct 22, 2026; state law applies from Jan 1, 2027 | None yet | None published | Not published | Web search, Oct 22, 2026; no county page located | Not covered yet |
What Two 800 Sq Ft ADUs Cost vs One
The cost engine below prices one 800 square foot detached ADU and two of them in four California cities, at standard finish. Look at the third column: it is exactly double the second. That is deliberate. Our engine prices each unit on its own and does not model shared trenching, one survey or one set of utility upgrades, so we will not claim a two-unit discount we cannot show.
| City | One 800 sq ft detached ADU | Two 800 sq ft detached ADUs | Typical, two units |
|---|---|---|---|
| Los Angeles | $281k to $468k | $562k to $936k | $748,800 |
| San Jose | $394k to $657k | $788k to $1,314k | $1,051,200 |
| San Diego | $311k to $519k | $623k to $1,038k | $830,400 |
| Sacramento | $259k to $432k | $518k to $864k | $691,200 |
Source: ADU Wizard cost engine, standard finish, all-in. Each unit priced separately; the engine does not model shared site work. Estimates, not bids.
That said, a second unit on the same lot often shares a utility trench, a sewer lateral and a site plan, so your real number may land below double. Get one bid for both units and one for a single unit and compare. Fees move too: an 800 square foot ADU is over the 750 square foot impact-fee line, and from January 1, 2027 SB 1117 charges those fees only on the space above 750. For size-by-size pricing see our 800 sq ft ADU cost guide, the 1,000 sq ft ADU cost guide and the California ADU cost page, and for fees, our ADU permit cost guide.
Should You Apply Now or Wait for 2027?
AB 956 does not say it applies to applications filed before January 1, 2027, and the law takes effect that day. So the practical choice looks like this:
- You want one detached ADU. Apply now. Nothing in AB 956 changes the one-unit path, and waiting buys you nothing.
- You want two detached ADUs. The state guarantee for the second unit starts January 1, 2027. A permit decision made before then is under 2026 law, where your city only had to approve one. Ask your city whether it will accept or hold a two-unit application filed in late 2026.
- Your ADU is over 750 square feet. Impact fee timing matters too. SB 1117 changes the fee math from January 1, 2027, and the statute does not say whether the date that counts is your application or when the city assesses the fee. Ask your city which date it uses.
If I were starting a two-unit project this fall, I would get the design and site plan done now and file the two-unit application in January.
How AB 956 Fits With SB 9, SB 1211 and SB 1117
- SB 9 is the other way to put more homes on a single-family lot: a lot split and up to two units per parcel. Two detached ADUs under AB 956 keep one parcel, so you cannot sell the ADUs separately unless your city has opted in to AB 1033. Our SB 9 page compares the two routes.
- SB 1211 sets the multifamily counts: up to eight detached ADUs on a lot with an existing multifamily building, never more than the existing units. AB 956 does not touch it.
- SB 1117, also effective January 1, 2027, limits impact fees on an ADU over 750 square feet to the area above 750, for up to two ADUs on a lot. Two 800 square foot units under AB 956 sit right in that window.
- For how big each unit can be, see California ADU size limits. For what a detached unit involves, see our detached ADU guide. For every 2026 bill in one place, see the California ADU law tracker, and for the statewide permit rules, the California ADU law and permits pillar.
Frequently Asked Questions
Can I build 2 ADUs on my property in California?
Yes, from January 1, 2027. AB 956 requires cities to approve two detached, new-construction ADUs on a lot with a single-family home, each cappable at 800 square feet of livable space. Through 2026, the state guarantee is one detached ADU plus one converted ADU and one JADU.
How many ADUs can you have in California?
On a single-family lot from 2027, the state guarantees two detached new-construction ADUs, or one detached ADU plus a converted ADU and a JADU, under Government Code Section 66323. On a multifamily lot, SB 1211 allows up to eight detached ADUs plus converted units. Cities can allow more.
When does AB 956 take effect?
January 1, 2027. AB 956 was approved and chaptered on September 29, 2026 as Chapter 791, Statutes of 2026, and it has no urgency clause.
Can I still build a JADU if I build two detached ADUs?
Maybe. Under the new Government Code Section 66323(b), a city does not have to ministerially approve a JADU on a lot where two detached ADUs were built under the AB 956 path. Your city can still choose to allow one.
Can my HOA block an ADU in California?
No. Civil Code Section 4751 voids HOA rules that effectively prohibit or unreasonably restrict an ADU, and from 2027 that covers any lot zoned to allow single-family use. The HOA can still impose reasonable restrictions, such as design rules.
Can I build three ADUs on a single-family lot?
It depends on your city and your lot. AB 956 guarantees two detached units. A third, whether a converted unit combined under Section 66323 or a detached unit under local standards, is not something we can promise until HCD or your city confirms it.
Does AB 956 apply to duplexes and apartment buildings?
No. AB 956 changes the single-family paragraph, Section 66323(a)(2). Lots with a multifamily building use Section 66323(a)(3) and (a)(4), the counts set by SB 1211, which AB 956 does not change.
Sources
- California Legislature, AB 956 (2025-2026), chaptered bill text: https://leginfo.legislature.ca.gov/faces/billTextClient.xhtml?bill_id=202520260AB956
- California Legislature, AB 956 (2025-2026), status (Chapter 791, Statutes of 2026): https://leginfo.legislature.ca.gov/faces/billStatusClient.xhtml?bill_id=202520260AB956
- California Government Code, Section 66323 (text in force through 2026): https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?sectionNum=66323.&lawCode=GOV
- California Civil Code, Section 4751: https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?sectionNum=4751.&lawCode=CIV
- California Civil Code, Section 714.3: https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?sectionNum=714.3.&lawCode=CIV
Disclaimer
This page is general information, not legal advice. AB 956 takes effect January 1, 2027, and cities will apply it through their own ordinances and forms. Confirm the current rules with your local planning department before you design or apply.
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