Insights

SB 1123 Lot Split Requirements: Up to 10 Homes on a Single-Family Lot

Oliver Thornton · October 24, 2026

General information only. This article is educational and is not legal, tax, financial, lending or investment advice. Do your own due diligence and confirm everything with your own qualified professionals before relying on it. Read the full disclaimer.

SB 1123 took the streamlined subdivision process that SB 684 created for multifamily land and extended it to vacant lots in single-family zones, effective July 1, 2025. On a qualifying site, an owner or developer can create up to ten small fee-simple lots and build a home on each, approved ministerially with no public hearing and no CEQA review.

This guide summarizes the requirements a single-family-zoned site has to meet. It is general information, not legal advice; local agencies implement the law through their own procedures, and the statute has already been amended once.

Requirements at a Glance

Requirement	SB 1123 (vacant single-family lots)
Zoning	Single-family residential zone
Site condition	Vacant (see below)
Maximum site size	1.5 acres
Maximum lots and homes	10 lots, 10 dwelling units
Minimum new lot size	1,200 sq ft
Average home size	No more than 1,750 net habitable sq ft
Side and rear setbacks	Capped at 4 ft from the original lot line
Lot width, depth, frontage	No local minimum may be imposed
Parking	No more than 1 space per home; none near qualifying transit
Ownership forms	Fee simple, common interest development, co-op, community land trust or tenancy in common
Approval	Ministerial; decision within 60 days of a complete application

What Counts as Vacant

The single biggest gate in SB 1123 is that the lot must be vacant. Under the statute, a lot can qualify if it has no permanent structure, or if its only permanent structure is abandoned and uninhabitable. A single-family lot with an occupied house on it generally does not qualify under SB 1123. That is the main reason developers on this pathway prefer multifamily-zoned lots under SB 684, where an existing house does not disqualify the site.

Site Exclusions

Like SB 684, SB 1123 screens out sites with environmental or safety constraints. A qualifying site generally cannot be in a high or very high fire hazard severity zone, an earthquake fault zone, a special flood hazard area or regulatory floodway, wetlands, protected species habitat, a hazardous waste site, or land under a conservation easement. At least 75 percent of the site’s perimeter must adjoin parcels developed with urban uses, and the site must be served by public water and sewer. A lot previously split under SB 9 or the Starter Home Revitalization Act is not eligible.

In Los Angeles, the fire hazard screen alone rules out most hillside lots, which is why SB 1123 projects concentrate in the flats.

Standards a City Can’t Exceed

The law limits what a local agency can require. Side and rear setbacks are capped at four feet from the original lot line, no separation is required between homes beyond building-code minimums, and a city cannot impose minimum lot width, depth or frontage. Floor-area limits cannot be set below a floor-area ratio of 1.0 for three to seven homes or 1.25 for eight to ten. Those floors are what make a ten-home plan possible on a lot a conventional subdivision would treat as one house.

What Makes an SB 1123 Site Work for a Developer

Qualifying is not the same as penciling. A small-lot developer will look for a site large enough for at least six homes, in a neighborhood where new starter homes sell well, with simple access and flat grades. Corner and street-to-alley lots are easier to plan. Because SB 1123 sites must be vacant, they are rarer than SB 684 sites, and they are worth flagging when you find one. If you own or represent a vacant single-family lot that might qualify, send it to us for a quick read.

Frequently Asked Questions

When did SB 1123 take effect?
July 1, 2025. It amended the Starter Home Revitalization Act created by SB 684.

Does SB 1123 apply to a lot with a house on it?
SB 1123 applies to vacant lots in single-family zones. A lot can count as vacant if it has no permanent structure, or if its only permanent structure is abandoned and uninhabitable. A lot with an occupied house generally does not qualify under SB 1123, though a multifamily-zoned lot with a house may qualify under SB 684.

How big can an SB 1123 site be?
No more than 1.5 acres, and the project can create no more than 10 lots and 10 homes.

What is the minimum lot size under SB 1123?
New lots created on a vacant single-family site must be at least 1,200 square feet.

Important Disclaimer

This article is published by Assemble Capital for general informational and educational purposes only. It is not legal, tax, accounting, lending, appraisal, real estate brokerage or investment advice, and it is not an offer to sell or a solicitation of an offer to buy any security. Laws, regulations, government programs, lending practices, market conditions and local procedures change often and vary by jurisdiction and by property. The information here may be incomplete, out of date or not applicable to your situation, and we have no obligation to update it.

No one, including investors, lenders, property owners, buyers, sellers, agents, brokers, wholesalers or developers, should rely on this article in making any decision. Before acting on any topic discussed here, independently verify the information and conduct your own due diligence with qualified legal, tax, financial, lending, appraisal and real estate professionals and the applicable government agencies.

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