Quick Answer
- Under the new California ADU laws for 2026, SB 543 requires a local agency to allow the unit categories in Government Code section 66323 in any combination.
- On a qualifying single-family lot, that means at least one conversion or interior ADU, one JADU, and one new detached ADU can be combined.
- HCD's March 2026 handbook also says the City must allow at least one section 66314 ADU in addition; that extra ADU may be attached or detached and can face objective local standards.
- This can produce three ADUs plus one JADU, but it is not automatic approval of any four-unit layout.
Header image: a conceptual illustration of a plausible California home and backyard ADU, not a parcel-specific or approved design.
What did SB 543 change for California ADUs?
The operative words are now in California Government Code section 66323: a local agency must ministerially approve any listed unit “or any combination” of those units. SB 543's enrolled text made that amendment effective January 1, 2026.
Before this change, some agencies read the statute's categories as alternatives. The March 2026 HCD ADU Handbook now states the statewide interpretation directly: on single-family lots, local agencies must allow at least an ADU created from existing space, one JADU, and one newly constructed detached ADU together.
The word attached needs care. The section 66323 unit is generally created inside proposed or existing space in the house or an accessory structure. A newly built attached ADU usually follows the separate section 66314 path and its objective City standards.
How many ADUs are allowed on a single-family lot in California?
| Approval track | Accessory unit | Core statewide condition | What can still vary |
|---|---|---|---|
| § 66323(a)(1) | One conversion or interior ADU | Within qualifying proposed or existing space; limited expansion may be used for access | Building, fire, and safety compliance |
| § 66323(a)(1) | One JADU | No more than 500 sq ft and entirely within the single-family residence | JADU requirements, sanitation layout, and owner-occupancy rules |
| § 66323(a)(2) | One new detached ADU | Up to 800 sq ft, with no more than four-foot side and rear setbacks | Statutory height rules and building-code review |
| § 66314 | At least one additional ADU | May be attached, within, or detached from the primary dwelling | Objective local design and development standards |
That last row comes from HCD's handbook, which says a local agency must allow at least one section 66314 unit in addition to the section 66323 units. Section 66314 allows an ADU to be attached to, within, or detached from the primary dwelling.
A practical single-family scenario
Suppose a homeowner has a qualifying house, an interior area that can become an ADU, enough space inside the house for a JADU, and a buildable rear yard. One code path could be:
- Convert qualifying interior space into one full ADU.
- Create one JADU within the single-family residence.
- Build one detached ADU under section 66323, capped at 800 sq ft.
- Propose one new attached ADU under section 66314.
This is the clearest answer to the 2026 question: yes, a qualifying lot can combine a detached ADU with a separate attached ADU. But the attached unit is not simply a second copy of the 800-square-foot detached rule. It follows a different statutory track, and the City may apply compliant objective standards to it.
Why “four units” is not a parcel guarantee
State law establishes ministerial approval paths. It does not prove that a particular floor plan, utility layout, or construction sequence complies. A real feasibility review still needs to test:
- whether the property is legally a single-family lot for State ADU Law;
- whether the proposed conversion area meets the statutory definition;
- whether a JADU can fit entirely within the residence;
- easements, utility capacity, drainage, fire access, and building separation; and
- the City's objective standards for the additional section 66314 ADU.
Do not ask only, “How many ADUs are allowed?” Ask the City to identify the statutory subsection it is applying to each proposed unit. That creates a reviewable record and prevents an attached ADU, conversion ADU, and JADU from being treated as interchangeable labels.
Check the City's current implementation
City pages are useful evidence, but they can be updated on a different schedule from state law and HCD guidance.
| City evidence | What the current official page says | How to use it |
|---|---|---|
| Sacramento ADU eligibility table | Distinguishes its local two-ADU path from a state-standard combination of one attached conversion, one JADU, and one detached ADU | Compare it with our Sacramento permit-process guide, then ask how the City is processing the additional § 66314 unit described by HCD |
| San Diego regulatory updates | Describes the City's current single-dwelling-unit implementation | Use our San Diego permit-process guide, then request written confirmation if the page and the 2026 HCD handbook use different combinations |
These City links are implementation evidence, not substitutes for the statewide statute. A City may offer a more permissive local route, but it cannot use a stale summary to erase a state-required unit category.
Your next action before design
Make a one-page parcel diagram showing the main house, existing accessory structures, candidate conversion area, proposed JADU area, detached footprint, attached footprint, property lines, easements, and utilities. Then send the diagram to the local permitting agency with one precise request:
Please confirm which proposed unit is being reviewed under Government Code section 66323(a)(1), section 66323(a)(2), and section 66314, and identify any objective standard that prevents the shown combination.
Once the combination is confirmed, separate permit feasibility from cost. Review how to read an ADU permit fee report, check the available California City guides, and use our research methodology before treating an early range as a government quote.
Own a duplex, fourplex, or apartment building instead? The count works differently. Read our California multifamily ADU rules and SB 1211 guide.
Common questions
Did SB 543 create the eight-ADU rule?
No. The multifamily rule allowing up to eight detached ADUs came from SB 1211 and became operative in 2025. SB 543's relevant 2026 change says the section 66323 categories may be combined.
Can the additional section 66314 ADU be attached?
Yes. Section 66314 allows attached, within, or detached ADUs. HCD says at least one section 66314 unit must be allowed in addition to section 66323 units, but compliant objective local standards may apply to that additional unit.
Does ministerial approval eliminate building permits?
No. Ministerial means review against objective requirements without a discretionary hearing. Building, fire, utility, and other applicable code reviews still remain.
How many ADUs can I build on my property?
On a qualifying California single-family lot, the 2026 state-law combination can reach three ADUs plus one JADU. The actual buildable count still depends on which statutory path applies to each unit and whether the parcel can satisfy building, fire, utility, access, and objective local requirements.