SB 9
2021 California law allowing ministerial lot splits and duplexes on most single-family lots.
Senate Bill 9 (2021) allows the owner of a single-family lot to (a) split the lot into two parcels and (b) build up to two units on each — for a maximum of four total units on what was originally one R1 lot. SB 9 review is ministerial, like ADUs.
The practical reality in LA is more complex than the headlines suggest: SB 9 lots must meet minimum size (typically 1,200 sqft per resulting parcel), cannot be in a historic district, and the owner must commit to occupy one unit for three years after a lot split. As of 2026, SB 9 production statewide is still under 1,000 units/year — far less than ADU production.
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FAQ — SB 9
What does "SB 9" mean in plain English?
2021 California law allowing ministerial lot splits and duplexes on most single-family lots.
Why does SB 9 matter for a California ADU or remodel?
SB 9 comes up in the California building code side of nearly every Greater LA and Bay Area project we touch. Senate Bill 9 (2021) allows the owner of a single-family lot to (a) split the lot into two parcels and (b) build up to two units on each — for a maximum of four total units on what was originally one R1 lot. Getting it right at design saves rework later — getting it wrong is one of the most common reasons permits stall.
Where will I see SB 9 on my own project?
Most owners run into SB 9 during the design or plan-check phase. Your project manager flags it on the schedule, walks you through what the city expects, and confirms documentation is in place before the inspection that depends on it.
Does SB 9 cost extra?
Sometimes — depends on whether it adds scope (a report, a structural detail, a fee) or just a paperwork step. Anything cost-impacting is itemized in your contract or change order, never buried in the invoice.
Who at Alpha Dream handles SB 9?
The project architect owns design-level decisions; the permit runner owns city interactions; the project manager owns field execution. You always know who to ask.