Cities Keep Banning Separate ADU Sales — State Law Requires an Exception

You built the ADU out back — or you're drawing one now — and you go looking for whether you could ever sell it on its own. Buried in the city's ADU code is a single flat line: your ADU "shall not be sold separately from the primary residence." No exceptions, no conditions. The door looks bolted shut.

Here's the thing: a blanket ban like that isn't what State ADU Law allows. The statute carves out a mandatory exception — and HCD keeps flagging city ordinances that drop the "no separate sale" line in without it.

What the statute actually requires

Government Code section 66341 doesn't leave cities a choice about whether the exception exists. It opens: "A local agency shall allow an accessory dwelling unit to be sold or conveyed separately from the primary residence to a qualified buyer if all of the following apply." The load-bearing condition: the ADU or the primary dwelling "was built or developed by a qualified nonprofit corporation," plus recorded affordability and tenancy-in-common terms.

Read it plainly: this is narrow — a nonprofit affordable-housing pathway with strings attached, not "sell your backyard unit to whoever you like." But a city still may not write the exception out of its code.

A broader route exists too. AB 1033, signed in 2023 and now Government Code section 66342, lets a city opt in by adopting an ordinance that allows an ADU and the primary home to be sold as condominiums. That one is optional — it only helps you if your jurisdiction has adopted it.

San Mateo: the flat ban, flagged

When HCD reviewed San Mateo's ADU ordinance, it landed on the separate-conveyance section. The ordinance said, "An ADU shall not be sold separately from the primary residence." HCD's finding was direct: Government Code section 66341 "creates a narrow exception to allow separate conveyance of an ADU to a qualified buyer if the property was built or developed by a qualified nonprofit corporation, among other things." Its instruction — "the City must amend the Ordinance to note these exceptions."

Verified against HCD's ADU Ordinance Findings letter to the City of San Mateo, dated October 18, 2024 (Finding 5, Section 27.19.030(a)).

The same line, city after city

San Mateo isn't unusual. HCD has flagged the identical absolute-ban wording in ordinance after ordinance:

• Calabasas — the ordinance said, "The accessory dwelling unit shall not be sold separately from the primary dwelling." HCD answered that State ADU Law establishes a local agency "shall allow an ADU to be sold or conveyed separately from the primary residence to a qualified buyer if all of the following apply" (Gov. Code § 66341), and that the ordinance "fails to reflect" that authority. (Finding 7, May 4, 2026.)
• Commerce — the ordinance said, "The accessory dwelling unit cannot be sold separately from the primary residence." HCD pointed to section 66341's requirement that jurisdictions "shall allow an accessory dwelling unit to be sold or conveyed separately from the primary residence" and told the City to provide for it. (Finding 10, May 20, 2024.)
• Santa Cruz — the ordinance said, "The accessory dwelling unit or junior accessory dwelling unit shall not be sold separately." HCD pointed to the state separate-sale provisions and ordered the code amended. (Section 24.16.150, February 6, 2024.)
• Emeryville — the ordinance said an ADU and its associated structure "may not be sold separately by conversion to condominiums, division of the lot on which they are located, or by other means." HCD found the same missing exception. (Section 9-5.1412(a), January 22, 2024.)

The two older letters cite the pre-2024 numbers (former section 65852.26) — SB 477 renumbered ADU law that March — but HCD reads them all the same way: an absolute ban with no exception doesn't comply.

What it means for your project

If your city's ADU code flatly bans separate sale with no carve-out, that line is out of step with the statute — and HCD's consistent position is that the exception belongs there. Two cautions. First, these are HCD enforcement letters — HCD's interpretation, not court rulings — and a city can adopt findings and push back. Second, the mandatory exception is genuinely narrow, and the broader condominium route only exists if your jurisdiction opted in under AB 1033; a missing ban is not a green light to list your ADU tomorrow.

So confirm two things with your building department or a land-use attorney before you plan around a sale: whether the exception could apply to you, and whether your city has an AB 1033 ordinance. This isn't legal advice. But the "no separate sale, period" line printed in a lot of California codes may not be the whole story.

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.