Research study
SB 9 lot splits and how they interact with ADU rights
Two routes to more units on one parcel. Use both and the statute stops guaranteeing you the ADU — and, separately, there are now two different bills called SB 9 in this area.
Written by HyreADU Research Desk Primary-source research and data analysis
Audited by HyreADU Research Desk Statutory citation and attribution audit
The finding
Stacking both SB 9 powers can cost you the ADU right you thought came with the lot. Government Code section 65852.21(f) provides that “[a] local agency shall not be required to permit an accessory dwelling unit or a junior accessory dwelling unit on parcels that use both the authority contained within this section” and the urban lot split authority.
Section 66411.7 separately provides that “a local agency shall not be required to permit more than two units on a parcel created through the exercise of the authority contained within this section” — and “unit” for this purpose is defined to include an ADU and a JADU.
So the two statutes are not additive, and the widely repeated “SB 9 gets you four units” is a description of what a city may allow, not of what state law requires it to allow. A jurisdiction is free to be more permissive. Many are not.
Uptake in the first year was very small, and that is Terner Center’s finding. Their study of thirteen California jurisdictions through November 2022 found Los Angeles with the most activity at 211 SB 9 unit applications, of which 38 were approved.
HyreADU calculation, for scale: the same city reported 7,390 ADU permit units to HCD in the same year. Where a homeowner has both routes available, the overwhelming majority take the ADU one.
There are also two bills called SB 9 in this space. SB 9 (Atkins), Stats. 2021, Ch. 162 — the HOME Act — is the urban lot split and two-unit statute this page is about.
SB 9 (Arreguín), Stats. 2025, Ch. 510, is a different bill on HCD review of local ADU ordinances. Nothing here is legal advice.
Before anything else: there are two bills called SB 9
SB 9 (Atkins), Stats. 2021, Ch. 162 — the HOME Act. The two-unit and urban lot split statute, enacted in 2021 and in force from 1 January 2022.
It sits at Government Code sections 65852.21 (two units) and 66411.7 (urban lot split). This is the SB 9 this page is about, and the one almost everybody means.
SB 9 (Arreguín), Stats. 2025, Ch. 510. A different bill, chaptered 10 October 2025, which amends Government Code section 66326 so that a local agency’s failure to submit an ADU ordinance to HCD within 60 days, or to respond to HCD findings within 30 days, renders the ordinance null and void.
It has nothing to do with lot splits. We cover it in the owner-occupancy study, where it is relevant.
Why this matters practically. California bill numbers reset each two-year session, so reuse is inevitable — but reuse within the same policy area is unusually damaging, because a reader who searches “SB 9 ADU” now gets results about two different statutes with no obvious signal telling them apart.
When you read a source citing “SB 9”, check the year and the author before relying on it.
When you write one, cite it as SB 9 (Atkins), Stats. 2021, Ch. 162, or SB 9 (Arreguín), Stats. 2025, Ch. 510.
Read this first
- Nothing here is legal advice, and we do not evaluate your parcel
Whether SB 9 is available on a specific lot depends on the parcel’s zoning, its history, prior sales, whether it is in an excluded area, whether tenants have occupied it, and the local implementing ordinance.
Those are facts about your property and questions for the planning counter and a land-use lawyer. We describe the statute and the published uptake data.
- The uptake data is Terner Center’s, not ours
The thirteen-jurisdiction table on this page was assembled and published by David Garcia and Muhammad Alameldin at the Terner Center for Housing Innovation in January 2023. We transcribe it, cite it and compare it to ADU permit counts. We did not collect it, and no part of it should be attributed to HyreADU.
- The uptake data is now three years old
It covers activity through November 2022 — SB 9’s first year. Local implementing ordinances have changed since, litigation has run, and the statutes themselves were amended by SB 1426 effective 30 June 2026. We could not locate a comparable multi-jurisdiction update, and we have not estimated one.
- Applications and permits are not the same event
Terner counted SB 9 applications and approvals. HCD counts permit events and completions. Setting them side by side shows a difference in scale that is far too large to be an artefact of definitions, but it is not a like-for-like ratio and we do not present it as one.
Two routes to more units, side by side
The ADU route and the SB 9 route are separate statutes with separate tests, separate approval mechanics and separate consequences for the title. The most common error is treating them as one program.
The ADU route
Governed by Government Code Chapter 13, sections 66310 to 66342. The unit stays on the existing parcel; nothing is subdivided and no new title is created.
State law sets floors a local agency cannot go below: an 850 square foot minimum permitted size, a 16-foot height floor, and a detached size cap of 1,200 square feet, with ministerial approval for the categories listed in section 66323.
An ADU may be rented separately but not sold separately, except through the nonprofit route or a local condominium ordinance adopted under the AB 1033 mechanism. There is no owner-occupancy requirement and a local agency may not impose one.
This is the route the overwhelming majority of California homeowners actually use, and the rest of this site is largely about it.
The SB 9 route
Two separate powers under SB 9 (Atkins), Stats. 2021, Ch. 162: a two-unit development right at section 65852.21, and an urban lot split at section 66411.7. They can be used singly or together.
The lot split creates new parcels with new titles. Section 66411.7 sets lot geometry rules: no resulting parcel smaller than 40 per cent of the original lot area, and both parcels at least 1,200 square feet.
It carries an owner-occupancy condition the ADU route does not: an affidavit that the applicant intends to occupy one of the units as their principal residence for at least three years.
And it carries the cap that this page exists to explain: no more than two units need be permitted on a parcel created through a lot split, with “unit” including an ADU and a JADU.
Both SB 9 sections were amended by Stats. 2026, Ch. 56 (SB 1426), effective 30 June 2026, and we retrieved them in that amended form. If you are reading an analysis written before mid-2026, check it against the current text.
The interaction, provision by provision
The table people actually need. Each row is a combination of powers; the middle column is what the statute requires a local agency to permit, which is not the same as what a particular city allows.
| What you use | What state law requires the agency to permit | Governing provision | Practical consequence |
|---|---|---|---|
| ADU statute alone | The ADU (and, where applicable, a JADU) on the existing parcel, to the state standards, ministerially where section 66323 applies. | Gov. Code Chapter 13, §§ 66310–66342 | No subdivision, no new title, no owner-occupancy condition, no three-year affidavit. The simplest route and by far the most used. |
| SB 9 two-unit right alone (no lot split) | Up to two units on the parcel under § 65852.21. | Gov. Code § 65852.21 | The ADU-blocking provision in subdivision (f) is triggered by using both powers. Using the two-unit right alone does not engage it. |
| SB 9 urban lot split alone | The split, subject to the lot geometry rules and the three-year owner-occupancy affidavit. | Gov. Code § 66411.7 | Two new parcels with separate titles. But § 66411.7’s two-unit cap then applies to each parcel created, and “unit” includes an ADU and a JADU. |
| Both SB 9 powers on the same parcel | The agency is not required to permit an ADU or JADU at all. | Gov. Code § 65852.21(f), verbatim: “A local agency shall not be required to permit an accessory dwelling unit or a junior accessory dwelling unit on parcels that use both the authority contained within this section” and the urban lot split. | This is the trap. A homeowner who splits the lot and builds two units under the two-unit right has, as a matter of state law, no guaranteed ADU right left on that parcel. |
| A lot split, then units on the new parcel | No more than two units per parcel created through the split. | Gov. Code § 66411.7, verbatim: “a local agency shall not be required to permit more than two units on a parcel created through the exercise of the authority contained within this section”, with “unit” including an ADU (§ 66313(a)) and a JADU (§ 66313(d)). | The ADU counts toward the two. A house plus an ADU on a split parcel is already at the cap, not a house plus an ADU plus more. |
Interaction of the SB 9 (Atkins) powers with the ADU statutes, from the statutory text as retrieved on 2026-09-05 — both SB 9 sections as amended by Stats. 2026, Ch. 56 (SB 1426), effective 30 June 2026.
Read the middle column as a floor, not a ceiling. Every one of these provisions says what a local agency is not required to permit.
A city may adopt a more permissive ordinance, and some have. The right question at the counter is not “what does SB 9 allow” but “what does this jurisdiction’s implementing ordinance allow, and where does it go beyond the state floor”.
This page cannot answer that for your city; the ordinance tracker is where we record what we have been able to read.
SB 9 in its first year: Terner Center’s thirteen jurisdictions
Assembled and published by David Garcia and Muhammad Alameldin of the Terner Center for Housing Innovation in “California’s HOME Act Turns One”, 18 January 2023, covering activity through November 2022. Their data collection and their finding; we transcribe it and attribute it.
| Jurisdiction | Lot split applications | Lot splits approved | SB 9 unit applications | SB 9 units approved |
|---|---|---|---|---|
| Anaheim | 2 | 0 | 1 | 0 |
| Bakersfield | 0 | 0 | 0 | 0 |
| Berkeley | 1 | 0 | 5 | 0 |
| Burbank | 1 | 0 | 7 | 2 |
| Danville | 20 | 13 | 0 | 0 |
| Long Beach | 1 | 0 | 1 | 0 |
| Los Angeles | 28 | 0 | 211 | 38 |
| Sacramento | 9 | 6 | 9 | 8 |
| San Diego | 3 | 0 | 7 | 0 |
| San Francisco | 4 | 2 | 25 | 4 |
| San José | 10 | 5 | 1 | 0 |
| Santa Maria | 0 | 0 | 0 | 0 |
| Saratoga | 21 | 2 | 15 | 1 |
SB 9 applications and approvals in thirteen California jurisdictions through November 2022. Source: Terner Center for Housing Innovation, “California’s HOME Act Turns One: Data and Insights from the First Year of Senate Bill 9”, Garcia and Alameldin, 18 January 2023, Table 1. Retrieved 2026-09-05.
Terner’s own scale comparison, quoted: “the city of San Diego permitted over 5,000 new homes in all of 2021 and Los Angeles permitted just under 20,000 new homes in 2021.” Their conclusion was that “SB 9 activity is limited or non-existent in these thirteen cities.” Note also the geography of the lot split column: the two highest counts are Danville (20) and Saratoga (21), small affluent jurisdictions, while Los Angeles produced 28 lot split applications and approved none of them.
Why homeowners take the ADU route instead
Terner’s planners had a hypothesis and it is worth quoting as theirs: that “more prescriptive state ADUs laws are likely pushing homeowners interested in creating new units towards ADUs,” and that SB 9 “currently … does not have this same flexibility.” That is a finding from their interviews, not ours.
HyreADU analysis. Looking at the two statutes side by side, four differences seem sufficient to explain the gap without needing any further mechanism. The ADU route requires no subdivision, so there is no map, no title work and no surveyor.
It carries no owner-occupancy condition, where the lot split requires a three-year principal-residence affidavit. It has an explicit ministerial pathway with statutory deadlines and statutory minimum sizes a city cannot undercut.
And it does not put the homeowner in the position of having created a separate saleable parcel next to their house, which is a materially different decision from adding a rental unit in the garden.
The scale evidence. The City of Los Angeles reported 7,390 ADU permit units to HCD in 2022. Terner recorded 211 SB 9 unit applications in Los Angeles in the same period.
San Diego reported 610 ADU permit units against seven SB 9 unit applications, San José 448 against one, and San Francisco 342 against twenty-five.
These are different administrative events, as we say repeatedly on this page — an application is not a permit — but no reasonable definitional adjustment closes a gap of that size.
What that means for the interaction rule. If almost nobody uses SB 9, the ADU-blocking provisions in section 65852.21(f) and section 66411.7 rarely bite in practice.
But they bite hardest on exactly the sophisticated projects most likely to attempt both routes, and they are the provisions most consistently missing from the “SB 9 means four units” summaries.
A rule that is rarely triggered and always misdescribed is worth writing down carefully.
The urban lot split rules, in the statute’s terms
Four provisions of Government Code section 66411.7 that decide whether a split is available at all, as retrieved on 2026-09-05. This is a description of the statute and not an assessment of any parcel.
- The two-unit cap on a created parcel
- Verbatim: “a local agency shall not be required to permit more than two units on a parcel created through the exercise of the authority contained within this section.” “Unit” is defined for this purpose to include an accessory dwelling unit under section 66313(a) and a junior accessory dwelling unit under section 66313(d). The ADU is inside the cap, not additional to it.
- The 40 per cent rule
- No parcel resulting from the split may be smaller than 40 per cent of the original lot area. This is what stops a lot split producing one usable parcel and one token strip, and it is the provision that makes SB 9 unavailable on a great many ordinary lots.
- The 1,200 square foot floor
- Both resulting parcels must be at least 1,200 square feet. Combined with the 40 per cent rule, this sets a hard minimum original lot size below which no split is possible.
- The three-year owner-occupancy affidavit
- The applicant must sign an affidavit stating an intention to occupy one of the housing units as their principal residence for a minimum of three years. This is a genuine difference from the ADU route, where a local agency may not impose an owner-occupancy requirement at all — see our owner-occupancy study for why that prohibition is now permanent.
HyreADU note: the affidavit provision is the one most likely to change the answer for an investor. An ADU can be built on a lot the owner does not live on.
A lot split, under the statute as retrieved, cannot be applied for on the same basis. Whether that is enforceable against a particular applicant in a particular jurisdiction is a legal question we do not answer.
What we could not verify
We could not locate a multi-jurisdiction SB 9 uptake dataset more recent than Terner Center’s first-year study covering activity through November 2022. Three and a half years have passed and we have not estimated what happened in them.
We did not assemble a list of jurisdictions that have adopted SB 9 implementing ordinances. Municipal code hosts blocked automated retrieval throughout this research program, and a partial list would imply a completeness we do not have.
We did not analyze SB 9 litigation, of which there has been some, and we make no statement about the statutes’ current enforceability in any jurisdiction.
We have not verified whether any specific city permits more than the state floor when both SB 9 powers are used. The statutory provisions describe a minimum; local ordinances may exceed it and some do.
Questions
Can I build an ADU on a lot created by an SB 9 lot split?
Does SB 9 really allow four units on a single-family lot?
Which is better for a homeowner, SB 9 or an ADU?
How many SB 9 lot splits have actually been approved?
Is there an owner-occupancy requirement for SB 9?
What is the minimum lot size for an SB 9 split?
Why do two different laws both get called SB 9?
Have the SB 9 statutes changed recently?
Written and audited by
HyreADU Research Desk
Primary-source research, data analysis and fact checking
We are a research desk, not a builder. We read the permit extract, the statute, the HCD return or the fee schedule ourselves, and publish each figure with its source and retrieval date.
Where a number cannot be traced to a primary source, we leave it out and say what we could not verify. Our store-based claims cover California only.
- CA
- the only state this desk will make store-based claims about
- 5
- jurisdictions with extracted ADU permit evidence
- 735
- CSLB-verified companies in the California store
- 0
- national claims from a one-state store
How this desk works
- Primary sources only. Permit counts come from the city or county that issued the permit. Production counts come from HCD’s Annual Progress Report. Rents come from HUD or the Census. We do not cite an article that cites a source; we download the source and compute the figure ourselves.
- This is a California site. The company store is 734 California firms and one New Mexico firm. Permit evidence exists for five named jurisdictions: Los Angeles, San Francisco, Sacramento, San José and unincorporated Marin. A number from that store is titled to those places, never to the United States.
- A permit is not a completion, and a license is not an ADU grade. California licenses no ADU classification. Being named on an ADU permit is evidence of engagement in that jurisdiction, not of quality, completion, or work anywhere else. Owner-builder permits are excluded from contractor counts.
- Calculation is labeled as calculation. Figures we derive are never presented as something HCD, HUD, the Census or a city published. Terner Center research is cited as Terner’s, never restated as ours.
- We do not design, permit or build ADUs, and we take no payment for placement, ranking or a favorable mention. Pages that look like rankings are not: they publish public-record counts and let the reader decide.
- Nothing here is legal, tax or financial advice. Zoning, underwriting and appraisal practice vary by jurisdiction, lender and appraiser. The useful next step on a specific lot is the planning counter and a licensed professional.
Data as of Government Code §§ 65852.21 and 66411.7 retrieved from leginfo 2026-09-05, both as amended by Stats. 2026, Ch. 56 (SB 1426) effective 30 June 2026; Terner Center first-year SB 9 study retrieved 2026-09-05; California HCD Annual Progress Report Table A2 extract, HCD file last updated 4 September 2026. Authorship on this site is organizational: the analysis belongs to the desk rather than to a named individual, and we do not publish credentials we do not hold.
Our editorial policy sets out how we source, date and correct what we publish.
Sources & retrieval dates
- California Government Code § 65852.21 — two-unit developments (SB 9, Atkins, Stats. 2021, Ch. 162) , Source of the verbatim provision quoted on this page: “A local agency shall not be required to permit an accessory dwelling unit or a junior accessory dwelling unit on parcels that use both the authority contained within this section” and the urban lot split authority. History note: amended by Stats. 2026, Ch. 56, Sec. 7 (SB 1426), effective 30 June 2026. Retrieved 2026-09-05.
- California Government Code § 66411.7 — urban lot splits (SB 9, Atkins, Stats. 2021, Ch. 162) , Source of the two-unit cap quoted verbatim, the 40 per cent lot area rule, the 1,200 square foot parcel floor and the three-year principal-residence affidavit. “Unit” includes an ADU under § 66313(a) and a JADU under § 66313(d). History note: amended by Stats. 2026, Ch. 56, Sec. 9 (SB 1426), effective 30 June 2026. Retrieved 2026-09-05.
- David Garcia and Muhammad Alameldin, “California’s HOME Act Turns One: Data and Insights from the First Year of Senate Bill 9”, Terner Center for Housing Innovation, UC Berkeley , Published 18 January 2023. Table 1 supplies the thirteen-jurisdiction lot split and unit application and approval counts through November 2022 transcribed on this page. Source of the quoted conclusions that “SB 9 activity is limited or non-existent in these thirteen cities”, of the scale comparison for San Diego and Los Angeles 2021 permits, and of the planners’ hypothesis that “more prescriptive state ADUs laws are likely pushing homeowners interested in creating new units towards ADUs”. Terner’s findings, cited as theirs throughout. Retrieved 2026-09-05.
- California Government Code, Title 7, Division 1, Chapter 13 — Accessory Dwelling Units , Sections 66310 to 66342, created by SB 477 (Stats. 2024, Ch. 7). Supplies the ADU-route provisions used in the comparison: the § 66313 definitions of “accessory dwelling unit” and “junior accessory dwelling unit” incorporated into § 66411.7, the § 66321(b)(2)(A) 850 sq ft floor, the § 66321(b)(4)(A) 16-foot height floor, the § 66314(d)(5) 1,200 sq ft detached cap and the § 66323 ministerial categories. Retrieved 2026-09-05.
- SB 9 (Arreguín, 2025) — Accessory dwelling units: ordinances. Stats. 2025, Ch. 510 , Chaptered 10 October 2025. Amends Gov. Code § 66326 so that failure to submit an ADU ordinance to HCD within 60 days, or to respond to HCD findings within 30 days, renders the ordinance null and void. Cited here solely to establish that a second, unrelated “SB 9” exists in this policy area. Retrieved 2026-09-05.
- California Department of Housing and Community Development, Housing Element Annual Progress Report — Table A2 , Full Table A2 extract, HCD file last updated 4 September 2026, deduplicated by tracking identifier. Supplies the 2022 ADU permit unit counts used in the scale comparison: 7,390 for the City of Los Angeles, 610 for San Diego, 448 for San José and 342 for San Francisco. Statewide, 26,224 ADU permit units in 2022 and 178,495 for 2018–2025. Retrieved 2026-09-05.
Check which SB 9 your source is talking about
Two live California statutes share the number, in the same policy area. Cite them with the year and the author, and check the interaction provisions before assuming an ADU right survives a lot split.
HyreADU does not design, permit or build accessory dwelling units, and does not practice law. This page is informational and is not legal advice.
It describes California statutory text as retrieved on 5 September 2026 and does not tell you what is permitted on any particular parcel; SB 9 availability depends on facts about the property, the local implementing ordinance and matters outside the scope of this page.
The thirteen-jurisdiction uptake table is the Terner Center’s data collection, published January 2023, and is cited as theirs; the comparison between SB 9 applications and ADU permit units is a HyreADU calculation of two different administrative events and is indicative of scale only.