What you can build

SB 9: building two homes and splitting your lot in California

Checked against state laws and official agency sources · Last reviewed October 9, 2026

What SB 9 lets you do

SB 9 (2021) added two sections to state law:

• Two-unit development (Government Code 65852.21). You can build up to two homes on a lot in a single-family zone, or add one new home next to an existing one. The city reviews it ministerially, meaning staff check it against objective rules with no hearing.
• Urban lot split (Government Code 66411.7). You can divide the lot once into two parcels through a parcel map, also approved ministerially.

You can use either one or both. HCD says that together they allow up to four housing units on a lot that typically holds one single-family home. The homes built under SB 9 are separate "primary units", not ADUs. [1][2][3][4]

Is your lot eligible?

Your lot must meet all of these:

• Single-family zone. The lot must be in a single-family residential zone. HCD says lots in multifamily, commercial, agricultural or mixed-use zones aren't covered even if they allow houses. Where a city has several single-family zones, the zone's primary purpose decides it, not its minimum lot size.
• Urban area. The lot must be in a city that includes part of a Census Bureau urbanized area or urban cluster. In unincorporated county areas, the lot itself must be wholly inside one.
• No disqualifying site conditions. SB 9 borrows the list of excluded sites from the state's streamlined-approval law (Government Code 65913.4) as it read on September 16, 2021. HCD's examples include farmland, wetlands, fire hazard areas, earthquake hazard areas, flood risk areas, conservation areas, wildlife habitat and conservation easements.
• No loss of protected housing. The project can't require demolishing or altering housing that is rent-restricted for moderate-, low- or very low-income households, under rent or price control, or occupied by a tenant in the last three years. It also can't be on a lot where the owner withdrew rental units from the market under the Ellis Act within the past 15 years.
• Historic limits. A two-unit project can't be in a contributing structure in a historic district, or on a parcel individually listed as a historic resource or local landmark. A lot split can't be on a state-listed or locally designated landmark property. It also can't require demolishing or altering a contributing structure, or an existing exterior structural wall, in a historic district.

HCD's September 2024 fact sheet describes the historic exclusion more broadly than the statute text current in 2026, so read the current law and confirm with your city's planning department. [1][2][3][5]

Lot split rules

• Roughly equal halves: The split creates no more than two new parcels of about equal size. Neither can be smaller than 40 percent of the original lot.
• Minimum size: Each new parcel must be at least 1,200 square feet, unless the city allows smaller lots by ordinance.
• One time only: You can't split a parcel that was itself created by an SB 9 split. You also can't use SB 9 if you, or anyone acting with you, already split an adjacent parcel under SB 9.
• Owner-occupancy affidavit: You must sign an affidavit "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 can't add any other owner-occupancy rule.
• No street dedications: The city can't require you to dedicate right-of-way or build offsite improvements as a condition of the split. It may require easements for public services and require each parcel to have access to, provide access to, or adjoin the public right-of-way.
• Residential use only: Uses on the new lots must be limited to residential.
• Map Act: The split must meet the objective requirements of the Subdivision Map Act, except where SB 9 says otherwise. The city can't require you to fix existing nonconforming zoning conditions to get approval.

[2]

What the city can and can't require

A city may apply objective zoning, subdivision and design standards, such as front setbacks, height, roof pitch or materials. These are rules with no personal judgment involved. But it can't apply them in a way that:

• physically prevents building two units on the lot (or on each new lot after a split)
• keeps either unit from being at least 800 square feet
• treats SB 9 projects more strictly than other development in the same zone

Setbacks: No setback can be required for an existing structure, or for one rebuilt in the same place and size. Otherwise the city may require up to 4 feet from the side and rear lot lines, and no more.

Parking: At most one off-street space per unit. None at all if the lot is within a half-mile walk of a high-quality transit corridor or major transit stop, or within one block of a car share vehicle.

Other conditions: If the units use a septic system, the city can ask for a recent percolation test. It can't reject a plan just because the two units are adjacent or connected, as long as they meet building code safety standards and could be sold separately. The city may adopt standards to protect a historic district listed in the California Register of Historical Resources. [1][2][3]

Deadlines and when a city can say no

The city must approve or deny a complete SB 9 application within 60 days. If it doesn't, the application is deemed approved. A denial must include a full written list of what is deficient and how to fix it.

To deny an eligible project, the building official must make a written finding, based on a preponderance of the evidence, of a "specific, adverse impact" on public health and safety that can't feasibly be mitigated or avoided. This is a high bar. The impact must be significant, quantifiable, direct and unavoidable, and based on objective written health or safety standards.

HCD's September 2024 fact sheet also mentions impacts on "the physical environment." The current statute text refers only to public health and safety.

SB 9 approvals are ministerial, so the California Environmental Quality Act (CEQA) doesn't apply to them.

Coming January 1, 2027: AB 2601 (2026) makes a two-unit application eligible for concurrent processing with a lot split application. It also lets a city hold building permits, grading permits or certificates of occupancy until the parcel map is approved and recorded. AB 2601 is a regular (non-urgency) 2026 law, so it takes effect on January 1, 2027. [1][2][3][6][7]

Combining SB 9 with ADUs

SB 9 and ADU law work together, with limits:

• If you split the lot: The city only has to allow two units on each new lot, and ADUs and junior ADUs count toward that two. Each lot could have two homes, or a home and an ADU, or a home and a junior ADU. The city may choose to allow more.
• If you don't split: You can have up to two SB 9 homes plus whatever ADUs and junior ADUs ADU law would otherwise allow. HCD notes this can add up to more units than either law alone. If ADU law is used, alone or with SB 9, to create more than four units on the lot, the city doesn't have to approve an SB 9 split.
• Using both SB 9 tools: On parcels that use both the two-unit rule and the lot split, the city isn't required to permit ADUs or junior ADUs.

For the ADU side of the rules, see California ADU rules and junior ADUs. [1][2][3][4]

Renting, enforcement and your city's rules

Any unit created under SB 9 must be rented for terms longer than 30 days.

Since January 1, 2024, HCD has had authority to enforce SB 9. In a May 2025 letter, for example, HCD told the City of Bellflower that two of its zones count as single-family zones for SB 9 and that the city had to fix their exclusion. HCD's Housing Accountability Unit Portal accepts requests to review potential violations of state housing law from any party.

Cities may adopt their own SB 9 ordinances with objective standards, so local details vary. See our city guides for Los Angeles, San Diego, San Jose, San Francisco, Sacramento, Oakland, Long Beach, Berkeley and Pasadena. [1][2][3][5][8]

Small-lot subdivisions (SB 684)

A separate law, Government Code 66499.41 (from SB 684, as amended), requires ministerial review of a parcel map or tentative and final map for a project of 10 or fewer parcels and 10 or fewer homes. It applies to a lot that is either:

• zoned for multifamily use, no larger than five acres and substantially surrounded by urban uses, or
• vacant, zoned single-family, no larger than 1.5 acres and substantially surrounded by urban uses

Under the version in effect through 2026:

• New parcels must be at least 600 square feet, or 1,200 square feet in single-family zones, unless the city allows smaller.
• The average home size can't exceed 1,750 net habitable square feet.
• The site can't be on farmland, wetlands, in a very high fire hazard severity zone, or in several other excluded areas.
• The city must approve or deny a parcel or tentative map within 60 days of a complete application.
• The city doesn't have to allow ADUs or junior ADUs on lots created this way, or an SB 9 split of them.

Laws passed in 2026, including SB 1090 and SB 1116, change several of these rules for applications received on or after January 1, 2027. The changes add lot-size averaging that allows some single-family parcels as small as 960 square feet, and new eligibility tests based on the site's base zoning. [9][10][11]

Questions people ask