California SB-10

California SB-10 is a state housing law that gives local governments an optional tool rather than a statewide entitlement. It lets a city voluntarily adopt an ordinance to upzone parcels — allowing more units per lot, up to roughly ten units — in transit-rich and certain urban-infill areas, with a streamlined process that can bypass some of the usual procedural friction. The defining feature is that SB-10 is permissive and local: it does not apply automatically anywhere.

This is the key distinction from SB-9. SB-9 grants a statewide, by-right path on qualifying single-family parcels regardless of whether a city wants it. SB-10, by contrast, only matters where a city has actually chosen to use it and has mapped which parcels it covers. As a result, SB-10 opportunity is concentrated in specific jurisdictions and specific areas, and it is up to each city whether to adopt it at all.

For builders, SB-10 is part of the toolkit for adding missing middle housing near transit, but acting on it requires knowing whether a given city has adopted an SB-10 ordinance and, if so, which parcels qualify. A first pass usually looks at whether a parcel sits in or near a qualifying transit area, but the real answer depends on the city's adopted ordinance and mapped boundaries.

Because adoption, eligible areas, and unit limits vary by jurisdiction and can change, this is informational only and not legal advice. Verify whether and where SB-10 has been adopted with the local planning department, and consult qualified counsel before relying on it for a project.