On March 4, 2026, the San Diego County Board of Supervisors voted unanimously to implement AB 1033, the state law (now Gov. Code §66342) that lets a city or county allow an ADU to be sold separately as a condominium. The county's program took effect April 4, 2026.
What AB 1033 Does in San Diego County
AB 1033 is a state statute. San Diego County's March 4 vote and April 4 effective date mean unincorporated areas of the county now permit separate sale of ADUs as condominiums. You build the ADU, then create condominiums through the county's Tentative Parcel Map or Tentative Map process under the Davis-Stirling Act. You need written consent from every lienholder (a lender can refuse), a safety inspection, and notice to the utilities. The main house and the ADU then become separately owned condos on the same parcel.
Before April 4, an ADU in unincorporated San Diego County was tied to the primary residence. You could rent it, you could live in it, but you couldn't sell it separately. The buyer of the main house got the ADU as part of the deal, whether they wanted it or not. AB 1033 removes that restriction in jurisdictions that adopt it.
The county posted an "ADU Condo Guidance & Checklist" to help applicants determine whether their unit qualifies for separate sale. The checklist walks you through Section 6156.x of the zoning ordinance and coordinates the tentative-map process with the condo-conversion workflow. If you're drawing plans for a detached ADU in unincorporated San Diego County today, your client may ask whether the unit can be sold separately. The answer is yes, if they follow the condo-map process.
Why This Matters for Spec ADU Builders
The separate-sale option changes the investment thesis. A homeowner who builds a detached ADU can now sell it, not just rent it, if every lienholder consents and the unit meets the county's requirements. The buyer gets a mortgage, moves in, and owns real property. The seller keeps the main house and reinvests the proceeds. That cycle didn't exist before April 4.
Small builders can build an ADU, create condominiums, and sell the ADU and the house separately, subject to the county's right-of-first-refusal, owner-occupancy affidavit and listing-posting rules (effective September 18, 2026). The pro forma depends on how quickly you can move through the tentative-map and final-map process, but the county's checklist suggests the pathway is navigable if you coordinate survey, title, and planning early.
Lenders care about exit strategy, and under AB 1033 every lienholder must consent in writing before the condo map is recorded. If the borrower can sell the ADU separately and pay off the loan faster, the risk profile changes. The ADU permit set and the condo map are separate processes, and both have to close before the sale can happen.
The August 19 Owner-Occupancy Amendments
After a June 12 Planning Commission hearing, the Board of Supervisors voted on August 19, 2026 to add three requirements for ADU condominiums, effective September 18, 2026: a right of first refusal for an existing tenant or another condo owner on the lot; an owner-occupancy affidavit from new buyers; and a required public posting period for each listing. The Board also asked staff to report back on enforcement and deed restrictions, so more changes are possible.
If you plan to build an ADU to sell, budget time for the right-of-first-refusal and posting steps, and expect buyers to sign the owner-occupancy affidavit.
That said, the April 4 implementation is live now, and the county's guidance materials are public. You can start the process today if your project qualifies.
What You Need to Submit
The county's ADU Condo Guidance & Checklist covers eligibility, but here's the short version:
- The ADU must be a legal accessory dwelling unit under current zoning.
- You file a tentative parcel map showing the condo boundaries.
- The map has to comply with Section 6156.x of the zoning ordinance and the county's subdivision standards.
- You coordinate with the county surveyor, planning, and—if there are utility easements or shared infrastructure—public works.
- Once the tentative map is approved, you record a final map and the ADU becomes a separately saleable condo unit.
A major coordination challenge is utility service. AB 1033 requires you to notify the water, sewer, gas and electric providers. If the ADU shares a water meter, sewer lateral, or electrical service with the main house, check the county checklist for any utility conditions on the map.
If you're working with a civil engineer on grading and drainage, loop them in early. The tentative-map submittal often requires a preliminary title report, a boundary survey, and a utility plan. The permit drawings we draft cover building code and zoning, but they don't replace the surveyor's work on the parcel map.
Who This Opens the Door For
First-time buyers priced out of single-family homes in San Diego County get a possible lower-priced entry point, and the county's new rules favor buyers who will live in the unit. The buyer gets a mortgage, builds equity, and owns real property. That's a different market than the rental-ADU market.
If you have equity but limited cash flow, check how the right of first refusal and owner-occupancy affidavit (effective September 18, 2026) affect any investor arrangement before you sign one.
Spec builders and small developers looking for lower-cost inventory are watching AB 1033 closely. Building a detached ADU on an existing lot is faster and cheaper than subdividing raw land, and the separate-sale option means you're not stuck holding a rental property if the market softens. Spec builders should model the September 18, 2026 rules: buyers sign an owner-occupancy affidavit, and an existing tenant or co-owner holds a right of first refusal.
What Happens in Other California Jurisdictions
AB 1033 is a state law, but it only applies where a city or county adopts an ordinance. San Diego County adopted one on March 4 (effective April 4). Before relying on separate sale anywhere else, including the City of San Diego, confirm the local ordinance.
If you're drawing ADU plans for a project in California outside unincorporated San Diego County, confirm whether the local jurisdiction has adopted AB 1033. If it hasn't, the ADU can't be sold separately, and your client's financing strategy changes accordingly.
Until your city or county adopts an ordinance, the separate-sale option doesn't exist there, even though the state law is on the books.
Next Steps
If you're a homeowner or investor in unincorporated San Diego County planning an ADU build, download the county's ADU Condo Guidance & Checklist and confirm that your project qualifies for separate sale. If you're working with a lender, show them the checklist and ask whether they'll underwrite a construction loan with AB 1033 conversion as the exit strategy. If you're a spec builder, line up a surveyor and a civil engineer who understand the tentative-map process, because the permit drawings are only half the puzzle.
The rules that took effect April 4 were amended effective September 18, 2026, and the Board has asked staff to report back on enforcement and deed restrictions. Check the county page before you start.
If you're starting an ADU project in San Diego County and want to confirm your design qualifies for AB 1033 condo conversion, reach out. We'll coordinate with your surveyor and make sure the permit set and the parcel map line up before you submit.