How Does SB 9 Work with ADUs? What Orange County and Los Angeles Property Owners Need to Know
If you own a single-family lot in Orange County or Los Angeles, you may have more development options than you realize — especially when SB 9 and ADU law are used together.
SB 9 (Gov. Code, §§ 65852.21 and 66411.7) and ADU Law are complementary. Both laws can be used together to create varying combinations of "SB 9 units" and ADUs. Understanding how they stack — and where the limits are — is one of the most important things an investor or property owner in this region needs to get right before breaking ground.
The basics of SB 9
SB 9 allows for a lot to be split, with each of the two resulting lots eligible for up to two primary units. These primary units are distinct from ADUs and JADUs created under ADU Law and must be approved ministerially — meaning the city cannot exercise discretionary judgment to deny them if you meet the eligibility requirements. If you're not sure whether your property qualifies, the Garden Grove SB 9 eligibility checklist walks through the urban lot split requirements in detail and applies equally as a framework across most OC cities.
When a lot split occurs
When a lot split occurs, SB 9 requires the local agency to approve up to two units on each parcel — but specifically states that only two units are allowed per parcel, despite what ADU Law would otherwise allow.
Those two units could be:
Two primary "SB 9 units," or
One primary unit and one ADU, or
One primary unit and one JADU
But in no case is a local agency required to permit more than two units on either of the two parcels resulting from an SB 9 lot split. The two-unit ceiling holds regardless of what ADU Law might otherwise allow on a parcel of that size or zoning type.
When no lot split occurs
When an SB 9 lot split has not occurred, the lot is eligible to receive up to two primary units under SB 9, as well as whatever combination of ADUs and JADUs it would otherwise be entitled to under California ADU Law. In some instances, this may result in a total number of units on the parcel that is greater than what either SB 9 or ADU Law would allow on its own.
This is the scenario that gets investors excited — and rightly so. In markets like Garden Grove, Anaheim, and Long Beach where lot sizes can support multiple structures, combining the two laws without a lot split can meaningfully increase density and rental income potential.
The four-unit ceiling on lot splits
There's one important limit to know. If ADU Law is used on its own or in combination with SB 9 to create more than four total units on the lot, a local agency is not required to approve a lot split under SB 9. So if you're planning to maximize density, sequence matters: pushing past four units before pursuing a lot split can close that door.
One more thing Los Angeles owners should know
Before you start the SB 9 process — whether you're going after a lot split or just the two-unit entitlement — make sure you're clear on the tenant protection requirements that come with the law. SB 9 has a built-in tenant protection clause that affects what you're allowed to demolish, and the City of Los Angeles has its own layer on top of that — including a required SB 9 Tenant Declaration Form that must be submitted as part of the application.
The combinations of what's possible under SB 9 and ADU Law are genuinely powerful — but only if you're working from an accurate read of the rules. For the full statutory framework, HCD's ADU Handbook is the definitive reference.
