Can You Sell an ADU Separately in California? AB 1033 and the Peninsula Opt-In Map

What AB 1033 Actually Changed

Before 2024, California ADU law came with a hard string attached: the ADU could not be sold or conveyed separately from the primary residence. You could build it, rent it, and house family in it, but at sale the lot moved as one asset with one buyer. AB 1033, signed in October 2023 and effective January 1, 2024, removed that prohibition conditionally. A city or county may now adopt a local ordinance allowing ADUs to be sold separately from the main home as condominiums, formed under the Davis-Stirling Common Interest Development Act and mapped in conformance with the Subdivision Map Act.

The word doing the work in that sentence is may. AB 1033 grants cities the power and changes nothing on its own. No ordinance, no separate sale. That makes the practical question for a Peninsula developer not “what does state law allow?” but “has this specific jurisdiction opted in?” And the honest answer is that almost none have.

Who Has Opted In, And Who Has Not

Statewide, the confirmed opt-in list as of July 2026 is three jurisdictions: San Jose, Santa Monica, and unincorporated San Diego County. Los Angeles, Sacramento, Oakland, and Long Beach are studying ordinances but have not adopted. Here is how that maps onto the markets we track:

Status as of July 2026. Opt-ins are moving through councils around the state, so confirm with the local planning department before you underwrite a separate-sale exit anywhere.

The Conversion Process In An Opted-In City

Where an ordinance exists, an ADU condo is a real subdivision of airspace, not a paperwork formality. The San Jose playbook, which tracks the statute’s requirements, looks like this:

1. Planning approval under the local ordinance. The ADU must be permitted and must meet whatever conditions the city attached to its opt-in. San Jose conveys qualifying units through a map recorded via its Public Works department.
2. A condominium plan or map. A licensed surveyor or civil engineer draws the unit boundaries and common area, and the plan records in conformance with the Subdivision Map Act. This is the document that turns one parcel into two sellable units.
3. Separate utilities. The ADU needs independently metered water, sewer, gas, and electric service, and the owner must give written notice to each utility provider of the creation and conveyance of the separate unit. If you are building new, stubbing separate services costs far less than retrofitting them later.
4. A safety inspection. The unit must pass a safety inspection before the condominium plan records.
5. Lienholder consent. Any lender with a deed of trust on the property must consent before the map records. On a construction loan this is a real gating item: raise it with your lender before you close the loan, not after the building is up.
6. CC&Rs and an HOA.The units become a common interest development under Davis-Stirling, which means recorded CC&Rs and a homeowners association to manage shared elements, even when the “association” is two owners on one former single-family lot.
7. Record and sell. Once the plan records, the ADU gets its own deed and title and can close to its own buyer.

Published estimates put the legal and filing side at roughly $15,000 to $30,000, before any utility-separation construction. The encouraging data point: San Jose’s first conversion reportedly moved through approvals in about 60 days. This is a process a spec builder can schedule, not an open-ended entitlement fight.

What A Sellable ADU Does To The ROI Math

Here is why this matters more than the short opt-in list suggests. Today, an ADU’s contribution to your exit is whatever an appraiser credits it on a single combined sale, which in practice means capitalized rent or a lump-sum adjustment, and both routinely come in below what the unit cost to build. The whole-property buyer pool also thins out at the top: the family paying for the main house often assigns near-zero value to a second kitchen in the backyard.

AB 1033 replaces that appraisal haircut with a second, independent exit. The San Jose comp is the proof: 749 sq ft cleared $530,000, about $707 per square foot, sold to an entry-level owner-occupant rather than valued off rent. Against detached-ADU all-in build costs that typically run well below that per foot, the spread is a development margin on a unit that used to be a cost-recovery question. Three consequences for how you underwrite:

• Teardown residuals move. If a rebuild can carry a detached ADU and the jurisdiction allows a condo exit, the project’s achievable finished value is house plus a separately-priced unit, not house plus an appraisal adjustment. Run it through the same inequality as any scrape-and-rebuild in the teardown pencil test: a second exit raises the right side, which raises the residual land value you can pay and still hit margin.
• It is a lot-split outcome without a lot split. An SB 9 urban lot split gets you two fee-simple exits, but only on parcels that clear the size, geometry, and owner-occupancy screens. AB 1033 condoization reaches a similar economic result on lots that fail those screens, at the price of an HOA and a thinner condo-buyer financing pool. Screen parcels for both paths: the SB 9 lot-split screener flags where the fee-simple route works, and where it does not, the condo route is the fallback to watch.
• Build separable now, even where you cannot sell yet.On the Peninsula outside San Jose, the rational move is optionality: if you are building an ADU anyway, separate meters, a detached footprint, and clean access cost little at construction time and make the unit convertible the day the city opts in. An ADU plumbed through the main house’s panel and water line is a retrofit project first and a condo second.

The honest caveats: one closed comp is a thin market, condo financing for sub-800 sq ft units is choppier than SFR financing, a mandatory HOA on a two-unit lot can drag slightly on the primary home’s resale, and an opt-in that has not happened is not an exit you can bank. Underwrite the separate sale as the base case in San Jose and as unpriced upside everywhere else on the Peninsula.

Finding The Parcels This Applies To

The lots where this option is worth real money share a profile: room for a detached unit, favorable setbacks, and a submarket where entry-level demand supports condo pricing. Our ADU feasibility screener ranks active San Mateo and Santa Clara County listings by exactly that buildability signal, and the SB 9 screener covers the parallel lot-split path. For the acquisition side of the same trade, the residual land value model is where a second exit shows up as a bigger number you can pay for the dirt.

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