SB 9 Lot Splits and Duplexes in Los Angeles.

Senate Bill 9 took effect January 1, 2022. It lets owners of many single-family lots build two homes, or split the lot in two, without a discretionary hearing. It is separate from ADU law, but the two interact.

LA ADU Guide is an information site, not a developer, lender or law firm. SB 9 has many eligibility tests. Confirm yours with the permitting agency.

Two different things

LADBS describes two SB 9 paths. It says SB 9 "adds Government Code Sections 65852.21 and 66411.7":

1. Two-unit development. A single-family zoned lot may have two dwelling units, attached or detached.
2. Urban lot split. An existing single-family parcel may be divided into two, which can be combined with a two-unit project "within certain limits."

LADBS also says objective standards may not "physically preclude" two units of 800 square feet each or an urban lot split. The City of Los Angeles Building and Residential Codes still apply in full.

Who issues the approval

In the City of Los Angeles, City Planning handles the lot split application and LADBS handles the building side. City Planning's checklist (CP-3605, revised April 2025) calls for a wet-signed SB 9 Urban Lot Split application (form CP-3604) and a preliminary parcel map. The map must carry a note that it is an Urban Lot Split under SB 9. Unincorporated areas follow LA County Regional Planning. Other cities, such as Long Beach or Pasadena, have their own SB 9 rules.

The details below come from the LA County summary, revised January 7, 2026, which applies to unincorporated areas. It restates state law, but the City of Los Angeles can differ in procedure and forms. Use it as a guide to the questions, not the City's answers.

Basic eligibility

For both paths, the County summary says the parcel must:

• Be in a single-family zone (for the County, R-1 or R-A, plus a few specific plan zones).
• Be vacant or have only one existing principal dwelling (two-unit path).
• Be a legal parcel wholly inside an urbanized area or urban cluster as defined by the US Census Bureau.
• Not contain units withdrawn under the Ellis Act within 15 years of the application.
• Not require altering or demolishing units that are rent-stabilized, income-restricted, or tenant-occupied in the three years before the application.

Where SB 9 does not apply

The County summary says a project is not permitted if any part of the parcel is in or contains, among other things:

• The Coastal Zone.
• Certain historic districts or landmarks.
• Wetlands, critical habitat or conservation land.
• A hazardous waste site not cleared for residential use.
• A delineated earthquake fault zone or FEMA flood zone, "unless" specified mitigation applies.
• A Very High Fire Hazard Severity Zone, or a High or Very High zone mapped by CAL FIRE, "unless all new and existing structures on the project site will be in compliance with fire hazard mitigation measures."

The same document adds that the site cannot lie within the boundaries of the Palisades and Eaton fires under Executive Order N-32-25. See ADUs in fire hazard zones for the ADU side of fire rules.

Urban lot split rules

From the County summary:

• Each new lot must be at least 1,200 square feet.
• Neither lot may be smaller than 40 percent of the original lot size.
• The parcel must not have come from a previous SB 9 lot split.
• The owner, "or anyone acting in concert with the owner," cannot have split or be proposing to split an adjacent parcel under SB 9.
• Both lots are barred from future SB 9 lot splits and are restricted to residential uses, with an exception for home occupations and cottage food operations.
• The applicant must sign an owner occupancy affidavit stating intent to live in one of the units "for a minimum of three years from the recordation" of the split.

City Planning's checklist adds that a split is approved only if it conforms to all applicable objective Subdivision Map Act requirements.

Setbacks, parking and rentals

Under the County summary:

• Existing structures keep their existing setbacks.
• Otherwise, side and rear setbacks are capped at four feet.
• One covered parking space per principal unit, but no requirement within one-half mile walking distance of a high-quality transit corridor or major transit stop, or when a car share vehicle is within one block.
• No unit may be used for short-term rental of 30 consecutive days or less.

Urban lot split at a glance

How SB 9 mixes with ADUs

On a parcel with a two-unit SB 9 project, units count as "any principal dwelling unit, ADU, or JADU." The County summary says no more than two units per lot in total, and on each lot created by a split. It says only one ADU or one JADU is allowed per new parcel when that parcel's only principal home is the one proposed or existing. So a split can produce up to four homes in total. Do not assume more. Local rules and the mix of unit types can change the count.

State ADU law is covered in California ADU rules. To see how permits proceed, read the LA permit process guide. The types of units are compared in ADU vs JADU vs garage conversion.

What we could not confirm

We did not find an official City of Los Angeles source for several details, including whether the three-year owner affidavit appears in City forms and how the City applies the fire zone test. Do not rely on a builder's marketing page for these points. Ask City Planning directly, or call 311, and keep the answer in writing.

Checklist before you start

• Find your zoning and overlays in the City's ZIMAS system and use its SB 9 eligibility checklist.
• Confirm the parcel is a legal lot. A Certificate of Compliance may be needed.
• Check for tenants, rent control and Ellis Act history.
• Check fire, flood, fault, historic and coastal maps.
• Ask how setbacks, parking and the owner affidavit work in your agency.
• Get a licensed surveyor and a licensed professional for the parcel map. See hiring an ADU builder for the licensing check.

More guides are in the ADU rules hub. This is general information, not legal advice.