What's the difference between an SB 9 split and an ADU? An ADU adds a second home to your lot that you own and usually rent out. An SB 9 split turns part of your lot into a separate legal lot you can sell, so someone else pays to build on it while you keep your house.
| Question | SB 9 lot split | ADU |
|---|---|---|
| What you end up with | Two separate legal lots | A second home on the same lot |
| Can you sell it on its own? | Yes, the new lot is its own parcel | Usually no. Only where the city has opted in to the 2023 ADU condo law (AB 1033) |
| Who pays to build | Agreed with the buyer of the new lot | You, usually with a loan |
| Approval | Ministerial, no public hearing | Ministerial, generally within 60 days |
| Live-in rule | Applicant signs a 3-year owner-occupancy statement | No owner-occupancy rule for ADUs (JADUs differ) |
| Short-term rentals | Rentals must be longer than 30 days | Cities may require rentals of at least 30 days |
| Your ongoing role | Homeowner on a smaller lot | Landlord |
An ADU means building a home yourself, usually with a loan, then renting it. The rent has to cover the loan, taxes, insurance, repairs and empty months, and you take on the landlord work.
An SB 9 split turns unused yard into cash from selling the new lot, with no construction loan on your side. Many owners use the money to pay down the mortgage. Our calculator runs both against your own numbers, and shows what a paydown could do to your payment.
An ADU can make more sense if you want to keep the whole lot, want rental income, or want a home for family. A split makes more sense if you'd rather have cash than a rental and less yard to keep up.
Usually not. California's 2023 ADU condo law (AB 1033) lets cities opt in to allowing it, and few have so far. An SB 9 split creates a separate lot you can sell.
State law lets cities limit each lot created by an SB 9 split to two homes, counting ADUs. Each city page lists its rule.
An SB 9 urban lot split generally requires the applicant to certify an intent to occupy one residential unit as a principal residence for three years, subject to statutory exemptions (such as qualified nonprofits and community land trusts). The obligation and its effect on a proposed sale should be reviewed for the specific applicant and transaction. ADUs have no owner-occupancy rule; junior ADUs do.
Both are ministerial. ADU permits are generally decided within 60 days; a split adds a parcel map, so it takes longer.
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General information, not legal, tax or financial advice. State law: Cal. Gov. Code §§65852.21, 66411.7. Last reviewed October 2026.