California SB-9 and SB-10 Explained: What Builders Need to Know

What SB-9 does

SB-9 was designed to add housing on land previously reserved for single-family homes. In broad strokes, it created two mechanisms for qualifying single-family parcels: the ability to split one lot into two (an urban lot split), and the ability to build up to two units on a parcel. Combined, these can allow significantly more homes on a lot that previously permitted just one house.

The headline feature for builders is ministerial, by-right approval for qualifying projects. Where a project meets the law's objective standards, the city is generally required to approve it without the discretionary review and public hearings that can add months or years and uncertainty. That predictability — not just the added density — is what makes SB-9 meaningful for people who build for a living.

General eligibility and common exclusions

SB-9 applies, in general, to parcels zoned for single-family residential use, and it comes with conditions and guardrails. Projects must typically meet objective standards the city sets, and there are well-known categories of land that are excluded or restricted — for example, properties in certain historic districts, and parcels in some environmentally sensitive or hazard areas such as certain fire or flood zones.

The law also includes provisions intended to prevent abuse and displacement, such as limits tied to recently occupied rental housing and an owner-occupancy intent affidavit associated with lot splits. These are described here only in general terms because the precise eligibility criteria, exclusions, and local objective standards vary and are subject to change. Treat any specific parcel as a question to verify with the city, not an assumption.

What SB-10 does

SB-10 is a different kind of tool. Rather than granting a statewide by-right entitlement the way SB-9 does, SB-10 gives local governments an option: it lets a city voluntarily adopt an ordinance to upzone parcels — allowing more units per lot — in transit-rich and certain urban-infill areas, with a streamlined path that can bypass some of the usual procedural friction.

The key distinction is that SB-10 is permissive and local. It does not automatically apply everywhere; it only matters where a city has actually chosen to use it. That means SB-10 opportunity is concentrated in specific jurisdictions and specific mapped areas, and you need to know whether and where a given city has adopted it.

How to tell if a parcel may qualify

For a quick first pass, builders generally look at a few things: whether the parcel is in a single-family residential zone (for SB-9), whether it sits in or near a qualifying transit area (relevant for SB-10 where adopted), and whether it falls into any of the common exclusion categories like historic or hazard designations.

But a first pass is exactly that. Zoning maps, overlay districts, local objective standards, and the city's own adopted ordinances all determine the real answer, and they differ block by block. The only reliable way to confirm whether a specific parcel qualifies — and under what conditions — is to check with the local planning department and, for anything consequential, get professional guidance. (Again: informational only, not legal advice — verify current statutes and consult counsel.)

Why SB-9 flags in permit data matter for builders

Knowing the law is one thing; finding where it's actually being used is another. When permit data carries SB-9 and SB-10 indicators, you can spot activity in eligible areas as it happens — lot splits, duplex filings, and small-scale infill — instead of discovering a project after it's already underway.

That early visibility is a competitive edge: it points you toward the neighborhoods and parcels where this kind of development is live, so you can focus outreach and bids where the opportunity is real. Igni flags SB-9 eligibility and SB-10 corridor signals on California permit records as part of its feed. You can explore California permit and ADU data and drill into specific markets like Los Angeles permit activity to see where this development is concentrated. To get access to filtered SB-9/SB-10 activity in your markets, request access.

Frequently asked questions