SB 10 is often lumped in with SB 9, but it works in the opposite direction. SB 9 overrides cities; SB 10 hands cities an optional tool. If a city chooses to use it, parcels near transit can be upzoned to as many as 10 units. Here is what it does and does not do.
What SB 10 Does
SB 10 gives local governments a streamlined option to upzone. A city or county may adopt an ordinance to zone a parcel for up to 10 units of residential density if the parcel is in a transit-rich area (generally within a half-mile of a major transit stop or on a high-quality bus corridor) or a qualifying urban infill site.
The appeal for cities is that adopting an SB 10 upzoning ordinance is streamlined for environmental review — the ordinance itself is not treated as a 'project' under CEQA, which removes a common legal chokepoint for rezonings. Note: that CEQA relief is for the ordinance; individual development projects still go through their own review.
It's Voluntary — That's the Whole Point
The single most important thing to understand about SB 10 is that it is opt-in. It does not automatically apply anywhere. Nothing happens under SB 10 unless a city or county affirmatively passes a resolution and ordinance to use it on specific parcels. Many jurisdictions have not adopted SB 10 at all.
So if you are evaluating a parcel, SB 10 only matters if (a) the parcel qualifies as transit-rich or urban infill, and (b) the city has actually chosen to upzone it under SB 10. Otherwise the base zoning controls.
SB 10 vs. SB 9: The Key Differences
These two 2021 laws are frequently confused. SB 9 is a by-right, statewide override: it forces cities to ministerially allow up to two units and a lot split on eligible single-family lots, whether the city likes it or not (subject to the charter-city litigation). SB 10 is the opposite — a tool cities may voluntarily use to upzone transit/urban parcels to up to 10 units.
Put simply: SB 9 is a mandate that limits local control; SB 10 is an option that expands local flexibility. SB 9 tops out around two-to-four units on single-family lots; SB 10 can reach 10 units, but only where a city opts in.
Limits and Timing
SB 10 has boundaries. The 10-unit ceiling is a maximum, not a guarantee; the city sets the height and other standards in its ordinance. Local governments cannot adopt new SB 10 ordinances on or after January 1, 2029. And because individual projects are not exempt from CEQA, a specific development can still face environmental review and other approvals. SB 10 also intersects with general-plan consistency and, in some cases, requires supermajority votes to override certain voter-adopted measures.
What Buyers and Investors Should Check
If a parcel's value depends on SB 10 density, verify two things with the planning department: whether the parcel qualifies (transit-rich or urban infill) and whether the city has adopted — or will adopt — an SB 10 ordinance covering it. Do not pay for density the city has not actually granted. Confirm the height and standards in any adopted ordinance, and budget for project-level review that SB 10 does not eliminate.
The Fine Print — This Is Not Legal Advice
Brian Cooper is a licensed REALTOR® with eXp Realty, not an attorney, land-use planner, or licensed surveyor. This guide is general educational information, not legal, tax, or land-use advice, and zoning law changes often. Zoning designations, overlays, and development standards are set and interpreted by each city or county, and state housing laws are actively litigated and amended. Before you buy, build, split, or invest, verify the zoning, overlays, and development feasibility for a specific parcel with the local planning department and confirm current state law — ideally with a land-use attorney or licensed professional.
Frequently Asked Questions
What is SB 10 in simple terms?
SB 10 is a 2021 California law that lets a city or county voluntarily adopt an ordinance to upzone a transit-rich or urban infill parcel for up to 10 residential units, with streamlined environmental review of the ordinance. It is optional — the city must choose to use it.
Does SB 10 apply automatically to my parcel?
No. SB 10 is opt-in. It only affects a parcel if the city or county has affirmatively adopted an SB 10 ordinance upzoning that parcel. If your city has not adopted SB 10, your base zoning controls. Confirm with the planning department.
How is SB 10 different from SB 9?
SB 9 is a statewide mandate that forces cities to allow up to two units and a lot split on eligible single-family lots by right. SB 10 is a voluntary tool cities may use to upzone transit/urban parcels to up to 10 units. SB 9 limits local control; SB 10 expands local flexibility.
How many units does SB 10 allow?
Up to 10 residential units per qualifying parcel, if the city adopts an ordinance to that effect. Ten is the maximum, not a guarantee; the city sets the actual height and standards in its ordinance.
Is there a deadline for SB 10?
Yes. Local governments cannot adopt new SB 10 ordinances on or after January 1, 2029. Ordinances adopted before then may remain in effect, but new adoptions stop at that deadline.
Does SB 10 remove environmental review for my project?
Not for the project itself. SB 10 streamlines CEQA review of the upzoning ordinance, but individual development projects on the upzoned parcel can still be subject to their own environmental review and approvals.
