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California AB 956, Signed This Week: Two Detached ADUs

Wang Jin

Founder, ADU Pilot

Bottom Line

AB 956 (Quirk-Silva) is Chapter 791, Statutes of 2026. It amends Government Code §66323 so that a local agency must ministerially approve two detached, new-construction ADUs on a lot with a proposed or existing single-family home, each with 4-foot side and rear setbacks. The city may cap each unit at 800 square feet of livable space. [1][2] It takes effect January 1, 2027. [4]

Three details matter more than the headline:

  1. It does not create a fifth unit. Once two detached ADUs are built, the city no longer has to approve a JADU. The state-guaranteed maximum on a single-family lot stays at the main house plus three ADUs. What changes is the mix: you can now trade the in-home JADU for a second backyard cottage. [1][5]
  2. Three ADUs on one lot lose SB 1117's fee break. SB 1117, signed the same day, charges impact fees only on the area above 750 square feet, but only for lots with up to two ADUs. A garage conversion plus two detached ADUs is three. Keep each unit at 750 square feet or less and the issue disappears. [12][13]
  3. Fire and building codes, not ADU law, decide whether your lot fits. By our own rough layout math, two 800-square-foot cottages need roughly 2,700 to 3,100 square feet of clear yard behind the house. On a standard 50-by-120-foot lot they fit only with tight gaps that, without fire sprinklers, require fire-rated walls with few windows. [9][10]

If your city's ordinance allows only one detached ADU, as many do, AB 956 is a real expansion. If you already have a JADU, read the section on the open legal questions before you design anything.

What Does AB 956 Change?

AB 956 touches three code sections. The core change is one word in §66323(a)(2), from "One detached" to "Two detached." The rest closes gaps around it. [1][6]

Provision Law through Dec 31, 2026 Law from Jan 1, 2027 (AB 956)
Detached new-construction ADUs approved ministerially on a single-family lot (§66323(a)(2)) One Two, each subject to an 800 sq ft cap and state height limits if the city imposes them
JADU on the same lot Guaranteed alongside one conversion ADU and one detached ADU ("1+1+1") Not guaranteed once two detached ADUs have been built (new §66323(b))
CC&R and deed-restriction protection (Civ. Code §714.3, §4751) Lots "zoned for single-family residential use" Lots "zoned to allow single-family residential use"
Ban on extra local standards, sprinkler exemption, 30-day minimum rental §66323(b)–(f) Same rules, renumbered §66323(c)–(g)

The second detached unit is what the state Department of Housing and Community Development (HCD) calls a "66323 Unit." These units are subject only to the standards listed in §66323. HCD's March 2026 ADU Handbook says they "do not have to comply with lot coverage, front setbacks, and design standards," and that cities cannot apply parking, lot size, open space, or floor area ratio rules to them. [7] They still have to meet building, fire, and health and safety codes.

The height limits come from §66321: 16 feet, or 18 feet within a half mile walk of a major transit stop or high-quality transit corridor, plus 2 feet there for a roof pitch matching the main home. [8] Most second cottages will be single-story.

AB 956 began in February 2025 as a placeholder bill on regional housing need and became the ADU bill on March 17, 2025. It passed the Assembly 58–4 in May 2025, the Senate 28–7 on August 25, 2026, and an Assembly concurrence vote 60–2 two days later. [1][3] California YIMBY sponsored it. The League of California Cities, the California Fire Chiefs Association, and more than a dozen cities opposed it, citing infrastructure capacity. [5]

The Four-Unit Cap: Why a JADU Drops Out

Section 66323 lets a homeowner combine the listed unit types. Before AB 956, the combination on a single-family lot was the "1+1+1" stack: one ADU converted from existing space, one JADU, and one detached ADU. For background on that stack, see our SB 543 multi-ADU playbook.

The 2025 Assembly version of AB 956 simply added a second detached unit. Senate Housing Committee staff flagged that this "could allow an existing single-family lot to be developed with five units," which could trigger the State Density Bonus Law. [5] The Senate's fix was new §66323(b): a city is not required to ministerially approve a JADU "on the same lot where two detached, new construction, accessory dwelling units have been constructed." [1] The Senate Floor analysis describes the result as "effectively maintaining consistency with SB 9's functional cap of four units per parcel." [5]

Configuration on a single-family lot Total homes Guaranteed under state law from 2027?
House + conversion ADU + JADU + 1 detached ADU 4 Yes (unchanged)
House + conversion ADU + 2 detached ADUs 4 Yes (new)
House + 2 detached ADUs + JADU 4 Unclear; see open questions below
House + conversion ADU + JADU + 2 detached ADUs 5 No. The city may allow it but does not have to

So AB 956 changes which units you get more than how many. A JADU is limited to 500 square feet inside the main house. A detached 66323 ADU can be up to 800 square feet, has its own entry and yard space, and carries no owner-occupancy rule. For many owners that swap is the whole value of the bill. Our JADU vs attached ADU comparison covers the trade-offs.

Cities can allow more than the state minimum. HCD's position is that a city must also allow at least one ADU under its local ordinance (§66314), which can carry local standards. [7] Whether that stacks on top of the configurations above depends on the ordinance.

Can I Fit Two Detached ADUs on My Lot?

State ADU law sets the setbacks at 4 feet, but it does not set the distance between buildings. HCD says local spacing rules may not "unreasonably restrict" ADUs "unless they are a requirement of a Building or Fire Code." [7] That exception is where most lots run out of room.

Fire separation. Long Beach's building department, applying California Residential Code Table R302.1, says an ADU wall closer than 5 feet to a property line generally needs fire-rated construction with limited openings, and that between two buildings on one lot the separation is the sum of each building's distance to an imaginary line between them. [9] Placer County puts it in numbers: an unsprinklered ADU needs a 1-hour rated exterior wall within 5 feet of a property line or 10 feet of another building on the lot; with sprinklers, 3 and 6 feet. [10] A 4-foot setback usually means a rated side wall with few windows.

Fire access. Los Angeles County Fire Department guidance requires every part of a new ADU to be within 150 feet of an approved access road, or 300 feet for a detached ADU with fire sprinklers. [11] A cottage at the back of a deep lot can fall outside that. Check your own fire department.

A rough layout test. This is our own geometry, not an official standard. Take a 50-by-120-foot lot with a 40-foot-deep house set 20 feet back. An 800-square-foot interior needs roughly a 22-by-40-foot footprint once walls are counted.

  • Side by side does not work: 4 + 22 + 22 + 4 = 52 feet, wider than the lot.
  • Front to back barely works. The house ends 60 feet back, and the rear setback leaves 56 feet. Two 22-foot-deep cottages use 44 of that, leaving about 6 feet behind the house and 6 feet between the cottages.

Gaps of 6 feet fall inside Placer County's 10-foot unsprinklered threshold, so without sprinklers the facing walls need fire ratings and few openings. With sprinklers, the 6-foot building and 3-foot property-line thresholds mean most walls can likely keep normal windows. [10] On a standard lot, sprinklers may decide whether the second cottage is livable. Keeping 10-foot gaps instead takes about 64 feet of clear depth.

The rule of thumb from this exercise is a clear rectangle about 48 feet wide and 56 to 64 feet deep behind the house, or roughly 2,700 to 3,100 square feet, within the fire department's access distance. Smaller lots have other options: smaller units, a second story where the 18-foot transit height applies, or placing one unit in the front setback, which HCD says 66323 units may use. [7]

AB 956 Fees: Impact Fees, School Fees, and the SB 1117 Catch

The exemption is written per unit. Government Code §66311.5 bars impact fees on an ADU with "750 square feet of interior livable space or less." Above that, fees are charged proportionately to the main home's square footage. [12] Two 750-square-foot cottages both pay zero impact fees.

SB 1117 (Chapter 809, signed September 29, 2026) changes that proportional formula from January 1, 2027. For "up to two accessory dwelling units on a lot," the fee on an ADU over 750 square feet is charged "only on the area in excess of 750 square feet." For "properties with more than two accessory dwelling units on a lot," the old whole-unit formula still applies. [13]

That creates a trap for the configuration AB 956 just made possible. A conversion ADU plus two detached ADUs is three ADUs. Here is an illustration with a 2,000-square-foot main home and a hypothetical $20,000 impact fee schedule for a new single-family home:

Detached ADU size Fee with 1–2 ADUs on the lot (2027) Fee with 3 ADUs on the lot (2027)
750 sq ft $0 $0
800 sq ft 50 ÷ 2,000 × $20,000 = $500 800 ÷ 2,000 × $20,000 = $8,000

The fix is simple if you plan for it: in a three-ADU layout, keep each unit at 750 square feet of interior livable space or less. JADUs are defined separately from ADUs in state law, so a JADU most likely does not count toward SB 1117's "two ADUs," but no agency has confirmed that reading. For the full fee picture, see our California ADU impact fees guide.

School fees follow a different threshold. ADUs with "less than 500 square feet of interior livable space" are exempt; larger units can be charged. [12] The State Allocation Board set the Level 1 residential rate at $5.38 per square foot in January 2026, so an 800-square-foot cottage could owe about $4,300 before any district Level 2 surcharge, and two of them about $8,600. [14] School fees are measured on assessable space inside the exterior walls, which is larger than interior livable space.

Utility connections are where detached units cost more than conversions. A city or water district cannot require a separate connection for a conversion ADU, but it can for a detached ADU, with fees "proportionate to the burden" based on square footage or plumbing fixture units. [12] Budget for two connections. See our utility connection glossary entry.

HOAs and the "Zoned to Allow" Fix

AB 956 also amends the two statutes that void CC&Rs and deed restrictions blocking ADUs: Civil Code §4751 for homeowners associations in planned developments and Civil Code §714.3 for other recorded instruments. [1][15][16] Both used to protect lots "zoned for single-family residential use." Senate committee staff noted that HOAs could read this to allow ADU bans on lots zoned for more than one unit, even when the lot holds a single house. [5] From 2027 the protection covers any lot "zoned to allow" single-family use, which brings in single-family homes in multifamily and mixed-use zones.

Two limits remain. First, §4751 still applies only to planned developments. A May 2026 draft extended it to all common interest developments, including condominiums, but the August 12 Senate amendments took that back out. [1][5] Condo owners gain nothing here. Second, HOAs can still impose "reasonable restrictions," meaning ones that do not unreasonably raise costs or effectively prohibit an ADU. Under §714.3, but not §4751, fees and other financial requirements are expressly excluded from that definition. [15][16] For the full HOA picture, including the Eng v. Opperman attorney-fee risk, see Can My HOA Block My ADU?

How AB 956 Interacts With SB 9, AB 1033, Fire Zones, and the Coast

SB 9 lot splits. On a parcel created through an SB 9 urban lot split, a city does not have to allow more than two units, counting ADUs and JADUs. [17] AB 956 does not help there. On an unsplit lot, HCD notes that if ADU law is used to create more than four total units, the city need not approve a later SB 9 split. [7] AB 956's guaranteed configurations stop at four, but adding a local-ordinance unit on top can cross that line.

Selling the units separately. Government Code §66342 lets cities adopt an ordinance allowing the main home and "accessory dwelling unit or units" to be sold as condominiums. [18] In a city that has opted in, both detached ADUs could in principle be sold, subject to lender consent, the Davis-Stirling Act, and a separate utility connection. See our AB 1033 guide and the glossary entry.

Very high fire hazard severity zones. AB 956 has no fire-zone carve-out, and HCD's position is that a city's area designations "cannot preclude units described in Government Code section 66323." [7] Fire separation, defensible-space, and road-access rules still apply and bite harder in fire zones. See our California fire zone ADU guide.

The Coastal Zone. ADU law does not override the Coastal Act, but under AB 462 a coastal development permit for an ADU must be decided within 60 days. [19] Coastal cities can condition a second cottage under their local coastal program. See our AB 462 analysis.

When Does AB 956 Take Effect, and Should I Apply Now?

AB 956 is not an urgency statute, so it takes effect January 1, 2027. [4] It has no transition rule for applications pending on that date, so do not count on a city applying it to a permit filed in 2026.

From January 1, §66323 applies regardless of the local ordinance, because it begins "Notwithstanding Sections 66314 to 66322." [1] A local ordinance that fails to meet state ADU law is null and void, and under the SB 9 (2025) amendments to §66326 an ordinance is also voided if the city does not submit it to HCD or respond to an HCD finding on time. [20][21] Expect counter staff and forms to lag, and cite "Government Code §66323(a)(2), as amended by AB 956 (Chapter 791, Statutes of 2026)" on your application. If the city stalls, our permit enforcement playbook covers appeals and HCD complaints.

How much this changes depends on your city. The City of Sacramento already allows two detached ADUs, but caps their combined size at 1,200 square feet, so AB 956 mainly loosens the size limit there. [22] Los Angeles County's May 2026 draft ordinance amendment proposes a 1,200-square-foot "Local ADU" alongside the state-exempt detached unit, which would have a similar effect in unincorporated areas. [23] San Diego has allowed extra units through its ADU Home Density Bonus Program, which the city scaled back in 2025; see our San Diego ADU guide. Where the local ordinance allows only one detached ADU, the change is substantial.

AB 956 lands in a market where ADUs are already a large share of new housing: 30,354 ADUs were permitted statewide in 2024, more than 26.6 percent of all homes permitted. [7]

Decision Framework: Is a Second Detached ADU Right for You?

You have a garage to convert and a deep backyard. This is the configuration AB 956 opens up: one conversion ADU plus two detached ADUs. Because that is three ADUs, design each one at 750 square feet of interior livable space or less to avoid impact fees under both current law and SB 1117. Price fire sprinklers early if the gaps between buildings will be under 10 feet.

You already have a JADU, or planned one. Get written confirmation from your planning department before designing two detached units. The JADU-first question below is unresolved, and a city may take the narrower reading.

Your lot is under roughly 50 feet wide, shallow, or in a fire zone. Run the fire separation and fire access test first. One larger detached ADU under your local ordinance, which many cities allow at 1,000 to 1,200 square feet, means one foundation and one utility connection.

You plan an SB 9 split. Decide on the split first. AB 956 adds nothing on split parcels, and going above four units can block a later split.

You are ready to permit one detached ADU now. Build it, but site it to leave room for a second unit in 2027. SnapADU, a San Diego builder, puts the second unit of a two-unit project at roughly 85 percent of the first unit's cost because of shared mobilization, a builder's rule of thumb rather than survey data. [24] Weigh that against the rent you would give up by waiting.

What Is Still Unsettled

These questions have no HCD guidance or case law as of September 30, 2026. Treat any confident answer you read elsewhere with caution.

  1. JADU first, then two detached ADUs. New §66323(b) applies where two detached ADUs "have been constructed." Read literally, a JADU that exists first stays protected. But §66323(a) now allows "any combination" only "except as provided in subdivision (b)," and the Senate described the change as technical, which supports reading it as a flat four-unit cap regardless of sequence. [1][5]
  2. Can the two "detached" ADUs touch each other? HCD has said detached ADUs on multifamily lots under §66323(a)(4) need not be detached from each other. [7] It has not said the same for single-family lots under (a)(2).
  3. Does a JADU count toward SB 1117's "two ADUs"? Probably not, given the separate definitions, but unconfirmed. [13]
  4. Pending applications on January 1, 2027. The bill is silent. [1]

HCD typically updates its ADU Handbook after major legislation. We will update this article when it does.

Frequently Asked Questions

Q: What does California AB 956 do?

A: From January 1, 2027, it requires cities to ministerially approve two detached, new-construction ADUs (up to 800 square feet each if the city caps them, with 4-foot side and rear setbacks) on a lot with a single-family home, instead of one. It also widens CC&R protections to lots zoned to allow single-family use. [1]

Q: Can I build two ADUs and a JADU under AB 956?

A: Two detached ADUs plus a JADU is legally unsettled. Two detached ADUs plus a JADU plus a conversion ADU (five homes) is not guaranteed: once two detached ADUs are built, the city does not have to approve a JADU. [1][5]

Q: When does AB 956 take effect?

A: January 1, 2027. It was signed September 29, 2026, and is not an urgency measure. [2][4]

Q: Do I pay impact fees on both detached ADUs?

A: Not if each is 750 square feet of interior livable space or less. Above that, SB 1117 limits the fee to the excess area only when the lot has no more than two ADUs. [12][13]

For the 2026 baseline on permits, fees, and owner-occupancy, see the California ADU laws 2026 guide. For financing two units, see How to finance an ADU in California. For multifamily lots, see the SB 1211 playbook. For SB 1117 and AB 1621, signed the same day, see our 2027 summary.

Disclaimer

This article reflects AB 956 and SB 1117 as chaptered and the law as of September 30, 2026. Neither bill takes effect until January 1, 2027, HCD has not yet issued guidance on either, and local building, fire, and planning requirements vary. Fee figures are illustrations, not quotes. Lot layout figures are our own estimates, not official standards. Consult a licensed California architect, land-use attorney, or your local planning department before making design or purchase decisions. Nothing in this article constitutes legal, financial, or construction advice.

References

  1. [1] California Assembly Bill 956 (Quirk-Silva), Chapter 791, Statutes of 2026, chaptered text. https://leginfo.legislature.ca.gov/faces/billTextClient.xhtml?bill_id=202520260AB956
  2. [2] Office of Governor Gavin Newsom. "Governor Newsom signs housing legislation, cementing California's record progress to reduce unsheltered homelessness and build more homes." September 29, 2026. https://www.gov.ca.gov/2026/09/29/governor-newsom-signs-housing-legislation-cementing-californias-record-progress-to-reduce-unsheltered-homelessness-and-build-more-homes/
  3. [3] AB 956 bill history, versions, and floor votes. https://leginfo.legislature.ca.gov/faces/billVotesClient.xhtml?bill_id=202520260AB956
  4. [4] California Constitution, Article IV, Section 8(c) (effective date of statutes). https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=CONS&sectionNum=SEC.%208.&article=IV
  5. [5] AB 956 committee and floor analyses, including Senate Housing Committee (June 2026), Senate Local Government Committee (June 26, 2026), Assembly Housing concurrence analysis (August 27, 2026), and Senate Floor Analysis (September 14, 2026). https://leginfo.legislature.ca.gov/faces/billAnalysisClient.xhtml?bill_id=202520260AB956
  6. [6] California Government Code §66323 (text in effect through December 31, 2026). https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66323.
  7. [7] California Department of Housing and Community Development. Accessory Dwelling Unit Handbook, March 2026. https://www.hcd.ca.gov/sites/default/files/docs/policy-and-research/adu-handbook-update.pdf
  8. [8] California Government Code §66321 (ADU height limits). https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66321.
  9. [9] City of Long Beach Building and Safety. FAQ-001, ADU fire separation distance (rev. August 21, 2024). https://longbeach.gov/globalassets/lbcd/media-library/documents/planning/adus-and-sb9/faq-001
  10. [10] Placer County. ADU building FAQ: fire-rated walls and separation. https://www.placer.ca.gov/FAQ.aspx?QID=1846
  11. [11] Los Angeles County Fire Department. EG-07, Accessory Dwelling Units (rev. November 26, 2024). https://fire.lacounty.gov/wp-content/uploads/2026/05/EG-07-Accessory-Dwelling-Units-ADUs-2024-11-26.pdf
  12. [12] California Government Code §66311.5 (ADU impact fees, school fee threshold, utility connections). https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66311.5
  13. [13] California Senate Bill 1117 (Cervantes), Chapter 809, Statutes of 2026, chaptered text. https://leginfo.legislature.ca.gov/faces/billTextClient.xhtml?bill_id=202520260SB1117
  14. [14] State Allocation Board. Index Adjustment on the Assessment for Development, approved January 28, 2026. https://www.dgs.ca.gov/-/media/Divisions/OPSC/Resources/CCI-Adjustments/01282026_Index-Adjustment-on-Development_Approved_FINAL.pdf
  15. [15] California Civil Code §4751 (ADUs in planned developments). https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=CIV&sectionNum=4751.
  16. [16] California Civil Code §714.3 (ADU restrictions in real property instruments). https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=CIV&sectionNum=714.3.
  17. [17] California Government Code §66411.7 (SB 9 urban lot splits). https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66411.7.
  18. [18] California Government Code §66342 (separate conveyance of ADUs as condominiums). https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66342.
  19. [19] California Government Code §66329 (ADUs in the Coastal Zone). https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66329.
  20. [20] California Government Code §66316 (non-compliant ADU ordinances null and void). https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66316.
  21. [21] California Government Code §66326 (ADU ordinance submission to HCD). https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66326.
  22. [22] City of Sacramento Community Development. Accessory Dwelling Units Handout, CDD-0423 (rev. January 29, 2026). https://www.cityofsacramento.gov/content/dam/portal/cdd/Building/Forms/CDD-0423_Accessory-Dwelling-Units-%28ADU%29-Handout.pdf
  23. [23] Los Angeles County Department of Regional Planning. 2026 ADU Ordinance Amendment, Single-Family Home Guide (proposed policy draft, May 2026). https://planning.lacounty.gov/wp-content/uploads/2026/05/2026-ADU-Ordinance-Amendment-Single-Family-Home-Guide.pdf
  24. [24] SnapADU. "ADU Costs" (builder estimate, updated March 2026). https://snapadu.com/adu-costs/

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