News Property Developement News


Understanding California SB9 (Lot Split) Legislation

How to use Senate Bill 9

Senate Bill 9 is a 2021 California state law that allows up to 4 homes in most single-family zones, regardless of local zoning. You can use SB9 to split your lot, add a 2nd home to a lot, or both (split lot and have 2 homes on each lot for a total of 4 homes).Here’s how you can build more homes once SB9 takes effect on Jan 1, 2022.Why use SB9?

*Earn money. Even if you don’t have the cash to build new homes yourself, you can sell your backyard to a builder or a future homeowner. Take a look at how much empty lots in your neighborhood sell for – it’s likely to be hundreds of thousands to over a million dollars.
*Do your part to solve California’s housing crisis. Maybe you have friends or family members that want a home but can’t afford one due to California’s high land costs. Homeownership is much more affordable if they’re only paying for a new building.


  1. Check if you’re eligible:
    ___ Property is zoned by the city or county for only 1 home. (if you want to subdivide a multi-family lot, use AB803)
    ___ Property is located in an existing urbanized area or urban cluster. See 2010 Census maps and 2020 Census additions. This includes most suburbs.
    ___ Not prime farmland or farmland of statewide importance, wetlands, conservation land, habitat for a protected species.
    ___ Not on a hazardous waste site, earthquake fault zone, 100-year floodplain or floodway.
    ___ Not a historic landmark or in a historic district.
    ___ Ellis Act was not used to evict tenants on any buildings on the property within the last 15 years.
    ___ If splitting the lot, you need to plan to live in either your existing house or one of the new homes for the next 3 years. This rule does not apply to land owned by community land trusts.

Homestead, a company that finances, designs, builds, & sells homes, has created a map search tool that homeowners can use to check if their lot is SB9 eligible.

Special Conditions

  • Fire Zones: Cannot use SB9 on land within a very high fire hazard severity zone, unless the development complies with state mitigation requirements.

  • Rental Housing: SB9 housing cannot demolish or alter housing that currently has a tenant or has previously had a tenant in the last 3 years. You cannot remove more than 25% of the exterior walls of such a building either, even if the rental unit is not altered. Affordable housing or rent controlled buildings on the property also cannot be demolished.

  • ADUs: If you already have one or more Accessory Dwelling Units on your property, you can still add a house to your lot if you don’t split the lot. However, ADUs count towards the maximum number of 2 homes per lot for split lots.

  • Septic Systems: If your property is not connected to a sewer system, the city or county may require a percolation test before allowing additional homes.

  • One lot split only: Lots created by a SB9 lot split cannot be further divided. Owners also cannot use SB9 to split adjacent lots.

  • No AirBNB’s: Homes created by SB9 can be sold or rented. However, if rented, the minimum rental is 31 days.

For full details see the bill text and 8/28/21 bill analysis

  1. Submit plans to city. Local regulations may require you to hire an architect. The city is required to approve SB9 projects at the staff level, without having to hold a public hearing.

  2. Sell and/or build. Not interested in managing the construction yourself? You can split the lot and sell the new lot without having to build on it.

In areas not near frequent transit or carshare, cities may require parking. However, lots in these areas are usually larger. As a workaround, you can rent your driveway to a carshare company.

Even if you can’t split the lot due to the existing house taking up most of the land, you can still build a 2nd home now… and split the lot later.

Another option is to build Accessory Dwelling Units instead of regular homes. These are smaller, but you can get to 4 homes this way without doing a lot split.

Regular dwelling unit, Accessory Dwelling Unit (ADU), or Junior ADU?
There are differences in permit fees, maximum size of the home, yard requirements, and other regulations, depending on how you classify the units when applying for a permit.

Regular Dwelling Units (houses and duplexes)
– Size and height limited only by existing zoning. Regulations may limit the size, but must allow exemptions if there’s no other way to have two 800 square foot units on a lot.
– Yard requirements defined by existing zoning, however, may reduce side and rear yards to 4 feet if no other way to fit two 800 square foot units.
– No parking required if within 1/2 mile of a major transit stop (rail, ferry, or Bus Rapid Transit), or 1/2 mile from a bus line with service at least every 15 minutes during peak hours, or within 1 block of carshare. Up to 1 parking space required per unit elsewhere.
– Restrictions apply on where you can build one. HOAs can also ban additional dwelling units.
Each home can be sold separately.

ADUs & Junior ADUs
– Exempt from other impact fees if less than 750 square feet.
– Exempt from school fees if less than 500 square feet.
– Can be built even if Homeowner Association rules don’t allow it, state law overrides HOA rules for ADUs.
Cannot be sold separately, unless it’s an ADU built by a nonprofit and reserved for low-income homeowners. JADUs can never be sold separately.
– Can be built in some places that SB9 units cannot be built, such as historic districts.

Can be attached to house or a detached structure in the yard.
No size limit, utility fees, or parking requirements if converted from space in an existing building.
– For new buildings, city can limit size to 800 square feet, and height to 16 feet. Otherwise the max size is 1,200 square feet for a detached ADU, or 50% of the area of the house / 800 square feet (whichever is more) for an attached ADU. Some cities may allow more.
– For new buildings, no parking required if within a 1/2 mile of any public transit, or within 1 block of carshare, or in a historic district, or in a parking permit district that does not offer permits to ADUs. Up to 1 parking space required per ADU elsewhere.

Junior ADUs
Max size: 500 square feet.
– Must be in same building as the main house. If adding a JADU to an existing house, must be built by carving out space from the house. A 150 square foot addition is allowed if needed to provide an entrance.
– Can share bathroom with main house.
– Kitchen can be an efficiency kitchen.
– City can require that the owner live on the property, either in the JADU or another home on the lot.

Further reading: State of California Housing and Community Development Department’s ADU Handbook at https://www.hcd.ca.gov/policy-research/docs/adu_december_2020_handbook.pdf

* To build a duplex and two detached ADUs, the duplex must be completed before a permit can be obtained for the ADUs.

Frequently Asked Questions

For Homeowners
Q: Can I rent out a home built using SB9?
A: Yes, as long as it is to a regular tenant. Short term rentals (30 days or less) are not allowed.

Q: Can I sell a home built using SB9?
A: Yes. Note that if you have more than 1 house on a lot, it will need to be sold as part of a duplex (though each home in a duplex can have a different owner), instead of a standalone house with its own land.

Q: Can I sell an Accessory Dwelling Unit using SB9?
A: Answer to this question is pending clarification from bill author.

Q: My property is zoned for 2 units. Can I use SB9?
A: No. However, you can use existing local zoning to build 2 homes and AB68 to build 2 Accessory Dwelling Units, for a total of 4 homes. Or, you can subdivide the lot using AB803, and have a house, ADU, and Junior ADU on each lot, for a total of 6 homes.

Q: I live in a Homeowners Association. Can I use SB9?
A: Depends on the HOA rules. SB9 overrides local zoning only. However, even if your HOA does not let you use SB9, you can still build an Accessory Dwelling Unit and a JADU using AB670.

Q: Can I use SB9 to split off a front or side yard?
A: Yes.

Q: My lot is not near existing transit or carshare. Can I meet the carshare requirement by renting out my driveway to a carshare company?
A: Yes.

Q: My neighborhood uses point-to-point carshare without fixed locations. Does that count as having carshare within a block?
A: Answer to this question is pending clarification from bill author.

Q: Can I list my car on a peer-to-peer carshare site to meet the carshare requirement?
A: Answer to this question is pending clarification from bill author.

Q: I am interested in doing a lot split and selling my yard. Who should I talk to?
A: Talk with a Realtor about listing your yard as a lot for sale. You may also want to hire an architect to analyze what is buildable.

Q: If I do a SB9 lot split, does the property get automatically re-assessed for property tax purposes?
A: No. Re-assessment only happens when there’s a new owner or new construction. If you sell your backyard to someone else, they will pay property taxes based on their purchase price. You might be able to request a downward reassessment of your house (and get a savings on future property taxes) if it’s now worth less with a smaller yard than its current assessed value.

For Future Homeowners
Q: I want to buy an existing vacant lot and build a custom home. Can I use SB9?
A: Yes. If you want to apply for a lot split as part of your project, you will need to sign an affidavit promising to live in one of the homes for at least 3 years.

Q: I am interested in buying a lot split to build a home? Who should I talk to?
A: While SB9 is new, the number of lot splits on the market will be limited. Instead, I would recommend starting with friends or family members who own a house but have extra yard space available.

For Tenants & Landlords
Q: Can a landlord use SB9?
A: Landlords can use SB9 to add a 2nd home to a lot that contains a house, as long as the lot is in single-family zoning. A landlord can also use SB9 to split a lot and add a 3rd & 4th unit, if they plan to live on the property for at least 3 years. A landlord cannot use SB9 to demolish or modify a tenant-occupied unit.

Q: Can I use SB9 and also build Accessory Dwelling Units?
A: No, unless the city specifically allows that. Note that under state ADU laws, it is possible to have 3 homes – the main house, a regular ADU, and a Junior ADU. See here for more information.

For Developers
Q: Can a developer use SB9 on a regular lot?
A: Developers can use SB9 to build 2 homes on a single family lot, but cannot use the lot split part of SB9, unless they plan to live in one of the homes. One workaround may be to leave half the yard vacant, and buy back the yard after selling the property to a homeowner.

Q: Can a developer use SB9 to buy a yard from a homeowner?
A: Yes, as long as the homeowner is planning to live on site for the next 3 years. However, the same developer cannot use SB9 to split adjacent lots.

For Architects
Q: What parts of local zoning does SB9 override?
A: The following:
– Density. Can have up to 2 homes per lot, for a total of 4 homes on 2 lots.
– Minimum lot size. Note that the new lot created using a SB9 lot split must contain 40-60% of the original lot. Unless local law allows otherwise, both newly created parcels must be no smaller than 1,200 square feet.
– Parking. None required if within 1 block of carshare, 1/2 mile of a Major Transit Stop (rail, ferry with bus or rail connection) or High Quality Transit Corridor (bus route with service of at least 1 bus every 15 minutes during peak commute hours). Elsewhere, the max parking a city can require is 1 space per unit.
– Yard requirements and other objective zoning or design standards that would have the effect of physically precluding the construction of up to two units or that would physically preclude either of the two units from being at least 800 square feet in floor area. Note that a a local agency may still require a setback of up to four feet from the side and rear lot lines.

Q: The existing lot and/or building is non-conforming to zoning. Can SB9 still be used?
A: Yes. Furthermore, if you are replacing a building that has a nonconforming setback, the new building can keep the same nonconforming setback as long as it’s in the same location as the old building.

Q: How does SB9 work with extra-large lots?
A: If a lot is large enough for a regular subdivision (for example, a 10,000 square foot lot in a zone that has a 5,000 square foot minimum lot size), you can first divide it using existing subdivision law. Then each of the lots can be SB9’d into two lots each – but only if it’s done by two different owners.

Q: Are there any restrictions on the shape of the lots in a lot split?
A: Cities can require that both lots have at least one edge adjacent to the street, but other than the rule that the smaller lot has to have at least 40% of the land of the original lot, odd-shaped lots are allowed.

Q: Can a mobile or manufactured home be used for any of the buildings?
A: Yes.

A 1-story pair of 800 square foot homes that can also be used as a single 1,600 square foot home.


Stacked Duplex
This is a stacked duplex with two 762 square foot two-bedroom homes that will fit in the back of most lots. The floor plan is designed so that the first floor unit can be wheelchair accessible.

All material on this page is CC-BY 4.0 Alfred Twu. You may freely copy and distribute this as long as you give me credit. Last updated Sept 16, 2021 Questions? Contact me at mail@firstcultural.com