Can I Split My Mar Vista Lot or Build a Second Home Under SB 9?

Often, yes. California's SB 9 lets the owner of a lot in a single-family zone do one of two things, or both. You can split the lot into two separate lots, or you can build up to two primary homes on the lot you already have. The city has to review a qualifying project ministerially, which means it is checked against written standards instead of going to a public hearing.

The catch is the word qualifying. Plenty of Mar Vista lots do qualify. Some do not, and the reasons usually have nothing to do with lot size. They come from the history of the house, who has lived in it, and whether it sits in a protected historic area. Here is how to tell which side of the line your property is on before you spend money on drawings.

SB 9 took effect on January 1, 2022, and it added two sections to the state Government Code. In the City of Los Angeles, the two paths it created go to two different offices.

• A two-unit development. Two homes on one single-family lot, attached or detached. Permit applications for these go to the Los Angeles Department of Building and Safety for plan check.
• An urban lot split. One single-family lot divided into two lots. These applications are filed with Los Angeles City Planning.

You can combine the two. According to the state housing department, when a lot is split under SB 9, the city must allow two units on each of the two new lots. On a lot that was not split, SB 9 allows up to two primary homes, and ADUs can still be added under the separate ADU law.

The state also set floors the city cannot build rules underneath. Local standards cannot stop you from building one or two homes of at least 800 square feet each. The city can ask for side and rear setbacks of up to four feet.

This is the part most owners skip, and it is where a plan usually falls apart. SB 9 does not apply if the project would demolish or alter housing that:

• is covered by a recorded covenant or law that keeps its rent affordable,
• is under any form of rent or price control, or
• has been occupied by a tenant in the last three years.

It also does not apply to a parcel where units were taken off the rental market under the Ellis Act in the last 15 years.

The historic piece matters in Mar Vista. SB 9 does not apply to a contributing structure in a historic district, or to a historic property or landmark under a local ordinance. Mar Vista has a historic overlay zone covering the Gregory Ain tract. If your home is a contributing structure there, SB 9 is not your path. The guide to Mar Vista's HPOZ explains what that overlay means for an owner.

Two more limits on lot splits. A lot that was already created by an SB 9 split cannot be split again. And you cannot split a lot next to one that you, or someone working with you, already split under SB 9. The law is built for one split per owner on adjoining land, not a string of them.

If you split the lot, you sign an affidavit. In it, you state that you intend to live in one of the homes as your principal residence for at least three years from the date the lot split is approved. Community land trusts and qualified nonprofits are the exception.

That promise shapes who SB 9 lot splits fit. It works for an owner who lives in the house and wants to stay. It fits poorly for someone who has already moved out, and it fits poorly for heirs who want to sell an inherited house quickly.

A two-unit development on an unsplit lot does not carry that affidavit. Whichever path you take, any rental created this way has to be rented for terms longer than 30 days, so short-term vacation rentals are out.

You can get most of the way to an answer in an afternoon. Here is the order I would go in:

1. Pull the SB 9 checklist on ZIMAS. City guidance points owners to an SB 9 eligibility checklist in ZIMAS, the city's free parcel lookup. The guide to using ZIMAS on a Mar Vista home walks through the screen.
2. Confirm the zone. SB 9 applies to lots zoned for single-family homes. If your lot is zoned for something else, this is the wrong tool.
3. Write down the occupancy history. Who has lived in the house for the last three years, and was any of it rented? A tenant in that window can end the conversation.
4. Check for historic status. If you are near the Gregory Ain tract, find out whether your home is a contributing structure.
5. Look at the lot itself. Width, depth, slope, and where the current house sits decide what a split or a second home could actually look like. A house in the middle of the lot often leaves no room for a usable second lot.

After that, a surveyor and an architect or designer who has done SB 9 work in the city can tell you what is buildable. Ask them for a rough cost before any drawings start.

Most of my conversations about SB 9 are really about a sale. An owner wants to know whether to split first and sell one lot, build first and sell two homes, or sell the lot as it is to a buyer who sees the potential.

Each path trades time and risk for a different result. Splitting and building means permits, construction, carrying costs and, for a lot split, a three-year living commitment. Selling as it is lets the next owner take that work on. What the right answer is depends on your timeline, your budget, and whether you want to stay.

A few things help either way:

• Know your eligibility before you list. A buyer who plans to split or build will ask. A clear answer, with the ZIMAS printout and the occupancy history ready, keeps the conversation simple.
• Keep the size rules separate. SB 9 decides how many homes and lots. The city's size limits for single-family homes still matter for what each new home can be. The article on Mar Vista's mansionization ordinance covers that side.
• Do not promise what the city has not approved. Marketing a lot as splittable before anyone has checked is how a sale ends up in a dispute.

If an ADU is closer to what you want, the guide to ADU rules and home value on the Westside covers that path.

Start with the ZIMAS checklist and the three-year occupancy history. Those two things answer more SB 9 questions than anything else. Then decide whether you are planning to stay and build, or planning to sell.

If you would like a second set of eyes on what your Mar Vista lot can do, and what it means for a sale, I'm here when you're ready. Send me a note and we can look at it together. No pressure, just real answers.