Your Backyard ADU Can Become the House on Its Own SB 9 Lot
Orange refused an SB 9 lot split because the new parcel would hold only an ADU. HCD's position: give applicants a pathway to convert it.
You own a single-family lot with a house up front and a backyard ADU you built a few years back. You want to use SB 9 to split the lot so the ADU sits on its own parcel — a real second home you could sell. You file the application, and the city won't process it: a new parcel can't hold just an ADU with no primary dwelling. Fine, you say — convert the ADU into a primary dwelling. The city's answer: there's no process in our code to do that.
Here's the thing: HCD's position is that an existing ADU doesn't make your lot ineligible for an SB 9 urban lot split — and when the fix is converting that ADU into a primary dwelling, the city has to give you a way to do it.
What happened in Orange
The property at 2025-2027 E. Walnut Avenue had a single-family residence in front and a detached structure in back holding a 640-square-foot ADU and a 441-square-foot garage, built in 2020. On October 8, 2025, the applicant filed an SB 9 urban lot split, proposing to put the ADU and garage on a newly created parcel, separate from the house.
The City of Orange declined to accept it. A parcel with only an ADU and no primary dwelling isn't permissible under ADU law (Gov. Code § 66313(a)), so the split as drawn couldn't stand. The applicant's fix was straightforward: convert the ADU into a primary dwelling, and the new parcel has its primary unit. But the City wouldn't do that either. In HCD's account of the exchange:
"…the City indicated that this cannot be done because the City code does not currently provide a process for approving such a conversion."
So the applicant was boxed in between two City positions: the split fails without a primary unit, and there's no way to turn the ADU into one.
What HCD said
HCD took the request for technical assistance and rejected the City's dead end. Its starting point: existing structures are normal. "This common circumstance does not provide a basis for ineligibility," the letter states. On the split itself, HCD is direct:
"The site eligibility criteria for an urban lot split do not include any restriction on the presence of existing ADUs or JADUs."
That's Gov. Code § 66411.7, the urban lot split half of SB 9 — a ministerial approval when the parcel meets the criteria. An ADU already on the lot isn't one of the disqualifiers.
On the conversion the City called impossible, HCD saw no reason for the wall:
"HCD sees no technical or policy outcome-based reason to prohibit the proposed conversion, provided the project meets local and statutory requirements."
And the bottom line, in HCD's words:
"In conclusion, the City must provide the applicant with a regulatory pathway to convert the ADU to a primary dwelling in order to process the urban lot split application."
"No process exists" isn't the end of the conversation. HCD's position is that the City has to build one.
Verified against HCD's Letter of Technical Assistance to the City of Orange, dated May 5, 2026, regarding the SB 9 urban lot split at 2025-2027 E. Walnut Avenue.
What this means if you're building
If HCD's read holds, an existing backyard ADU is not a reason a city can refuse your SB 9 lot split — and "we have no procedure for that" is not a reason to leave you without one. HCD noted the City can still apply objective design and improvement standards that conform to statute (§ 66411.7(c)(1)), and that a denial requires specific public-health-and-safety findings (§ 66411.7(d)). HCD asked Orange to respond by June 5, 2026.
But read this for what it is. A Letter of Technical Assistance is HCD's interpretive position — guidance, not a court ruling. HCD has enforcement authority over SB 9 and can refer a noncompliant jurisdiction to the Attorney General under Gov. Code § 65585(j), but courts are the final word on what the statute requires. If a city is blocking your lot split over an existing ADU, or telling you a conversion can't be processed, this letter is worth putting on the table — then verify with your planning department and your own land-use counsel before you rely on it. None of this is legal advice.
What CrossBeam does with it
When the letter lands on your desk, CrossBeam turns it around the same day: what each item is actually asking, the code or law behind it, and a written response you can hand to your team or your attorney — the back-and-forth that used to eat weeks, done in a couple of hours.