State Law | SB 9 (2021)

California SB 9 (2021): Two Homes and a Lot Split, Step by Step

SB 9 (2021) is the California law that lets you build two primary homes on a lot in a single-family zone, split that lot into two, or do both. The city must use ministerial approval: staff check your plans against fixed written rules and approve them if they comply, with no public hearing. This page is the owner's guide to using it in 2026, from the first eligibility check to the 60-day decision. For how SB 9 compares with zoning laws in other states and countries, see VanPlex's SB 9 policy comparison page.

What SB 9 Is

SB 9 is Chapter 162, Statutes of 2021, and it took effect on January 1, 2022. It added two sections to the Government Code. Section 65852.21 covers two homes on one lot. Section 66411.7 covers the "urban lot split," which divides one lot into two. The California Department of Housing and Community Development (HCD) says in its SB 9 Fact Sheet that the law "facilitates the creation of up to four housing units in the lot area typically used for one single-family home."

Two different California bills carry the name SB 9. The lot split law is SB 9 of 2021. SB 9 of 2025 (Chapter 510, Statutes of 2025) is a separate bill about city ordinances on accessory dwelling units (ADUs). This page is about the 2021 law only.

Both SB 9 sections were last amended by SB 1426 (Chapter 56, Statutes of 2026), effective June 30, 2026. That bill's own summary says it makes "nonsubstantive changes" to the annual-report wording, so the rules owners use did not change in 2026. HCD has had power to enforce both sections since January 1, 2024, under AB 434 (Chapter 740, Statutes of 2023).

SB 9 Rules at a Glance

Sources: Gov. Code 65852.21, Gov. Code 66411.7 and the HCD SB 9 Fact Sheet.

Step 1: Confirm Your Lot Qualifies

SB 9 applies only to a lot in a single-family residential zone, in a city whose boundaries include part of a US Census Bureau urbanized area or urban cluster. HCD says lots in multifamily, commercial, agricultural or mixed-use zones are out, even if those zones allow a house. The project also cannot sit on excluded land: HCD lists "farmland, wetlands, fire hazard areas, earthquake hazard areas, flood risk areas, conservation areas, wildlife habitat areas, or conservation easements."

Three rules cover the people and the history of the property. The project cannot demolish or alter housing under rent control, under an affordability covenant, or "occupied by a tenant in the last three years." A lot where an owner used the Ellis Act to take units off the rental market in the past 15 years is out. And since January 1, 2026, AB 1061 excludes a contributing structure in a historic district, an individually listed historic resource and a local landmark. The eligibility page runs through every check.

Step 2: Choose Two Homes, a Split, or Both

The two sections work alone or together. Without a split, you keep one lot with two primary homes, and you can add ADUs and junior ADUs on top under state ADU law. With a split, you get two lots that can be sold separately, and the city has to allow only two units on each new lot. ADUs and junior ADUs count toward those two. HCD sums up the result: "in no case does SB 9 require a local agency to allow more than four units on a single lot, in any combination of primary units, ADUs, and Junior ADUs."

The choice depends on your goal. If you want to keep and rent all the homes, the two-unit section has no owner-occupancy affidavit. If you want to sell a home on its own lot, you need the split and its three-year affidavit. The duplex to fourplex page shows each combination.

Step 3: Do the Lot Split Math

The statute asks for two lots of "approximately equal" area. In numbers, Government Code 66411.7 says neither new lot may be smaller than 40 percent of the original lot, and each must be at least 1,200 square feet unless the city adopts a smaller minimum by ordinance. At the state default, the original lot needs at least 2,400 square feet. On a 5,000 square foot lot, the smaller lot must be at least 2,000 square feet, and the larger one at most 3,000.

Each new lot must have access to the public right-of-way, which means a street or alley, and the city may require easements for utilities. The city cannot require you to give land for a street or build off-site improvements as a condition of the parcel map, the recorded map that creates the new lots.

Step 4: Design Within the State Limits

Cities may apply objective zoning, subdivision and design standards, meaning written rules with numbers or yes-or-no tests, such as height and lot coverage. SB 9 sets limits on those rules. A standard cannot physically prevent two units, and it cannot keep either unit under 800 square feet of floor area. Since SB 450, the standards must also apply the same way across the whole zone.

Side and rear setbacks, the required gap between a building and the property line, can be no more than four feet. HCD's fact sheet calls this "an across-the-board maximum four-foot side and rear setbacks." No setback can be required for an existing structure, or for one rebuilt in the same place and to the same size. That lets you convert a garage on the property line.

Parking is capped at one off-street space per unit. The city can require none at all if the lot is within one-half mile walking distance of a high-quality transit corridor or a major transit stop, or if a car share vehicle is within one block.

Step 5: Sign the Paperwork

For a lot split, the applicant signs an affidavit "stating that the applicant intends to occupy one of the housing units as their principal residence for a minimum of three years from the date of the approval of the urban lot split." Community land trusts and qualified nonprofits are exempt. The city cannot add any other owner-occupancy rule. The two-unit section, 65852.21, has no affidavit.

Expect two more conditions. Any rental of an SB 9 unit must be for a term longer than 30 days, so nightly rentals are out. Lots created by a split are limited to residential uses. Some cities, San Jose among them, also ask for a signed statement on tenant history and a recorded deed restriction on short rentals. Check your city's checklist.

Step 6: The 60-Day Decision

Under SB 450 (Chapter 286, Statutes of 2024), signed September 19, 2024 and in effect since January 1, 2025, a city must approve or deny a complete SB 9 application within 60 days of receiving it. If it misses the deadline, the application is "deemed approved," which means the law treats it as approved. A denial must come with a written list of the defects and a description of how to fix them.

The grounds for denial are narrow. A city may deny an SB 9 project only if its building official makes a written finding, "based upon a preponderance of the evidence," that the project would have a "specific, adverse impact" on public health and safety that cannot be reduced. The California Environmental Quality Act (CEQA), the state environmental review law, does not apply, because the approval is ministerial. In the coastal zone the Coastal Act still applies, but the city does not have to hold a public hearing on the coastal permit.

What SB 450 Changed in 2025

SB 450 made four changes that took effect January 1, 2025. It added the 60-day deadline. It removed the old rule that blocked a project demolishing more than 25 percent of the existing exterior structural walls, so a full rebuild is possible when no other SB 9 limit applies. It removed "physical environment" as a reason to deny. And it required city standards to apply uniformly within the zone.

SB 450 also rewrote the law's findings. They now say the housing shortage is "a matter of statewide concern and not a municipal affair" and that the law applies "to all cities, including charter cities." That language matters for the court case below.

The Charter City Case

Five charter cities, Redondo Beach, Carson, Torrance, Whittier and Del Mar, sued the state. Charter cities run under their own local charter and control some local matters. On April 22, 2024, Los Angeles Superior Court Judge Curtis A. Kin ruled for them in case 22STCP01143, according to a City of Santa Monica update. The judgment, entered June 18, 2024, declared SB 9 unconstitutional and ordered the state to stop enforcing it against the five cities. The Attorney General filed a notice of appeal on June 21, 2024.

On November 12, 2025, the Court of Appeal, Second District, Division Four, in case B338990, reversed the judgment and sent the case back to the trial court to reconsider under the law as amended by SB 450. It also reversed the order on attorney fees. VanPlex found no later ruling from the trial court as of October 5, 2026. If your lot is in one of the five cities, ask the planning department whether it is processing SB 9 applications. Every other city remains subject to SB 9.

Starting January 1, 2027: AB 2601

AB 2601 (Chapter 955, Statutes of 2026) was chaptered on September 30, 2026 and takes effect January 1, 2027. It makes a two-unit application eligible for processing at the same time as an SB 9 lot split. It lets the city hold building permits, grading permits or certificates of occupancy until the parcel map is approved and recorded. And it says the parcel map may include a condominium plan if the owner proposes one, so each home can be set up for separate sale through the same map.

How Often Owners Use SB 9

The available data shows limited use. The Terner Center at UC Berkeley surveyed 13 cities through November 2022. Los Angeles received 211 applications for new SB 9 units in 2022 and San Diego received seven. Saratoga reported 15 unit applications and 21 lot split applications, and Danville 20 lot split applications. The Center concluded that "the impact of SB 9 has been limited so far." HCD's open data does not include a statewide SB 9 count.

Cities write their own procedures on top of the state law. Los Angeles sends two-unit permits to its Department of Building and Safety and lot splits to City Planning; San Diego calls the two-unit project a Multi-Dwelling Unit Development; San Jose requires an existing home on the lot before a split records. See the Los Angeles, San Diego and San Jose pages for the local rules.

Where to Go Next

Related on VanPlex: California SB 9 in the global multiplex zoning comparison and the laneway and ADU guide for British Columbia.

Frequently Asked Questions

Official sources (checked October 2026)