SB 684 and SB 1123: Small-Lot Subdivisions of Up to 10 Homes
SB 684, the Starter Home Revitalization Act, lets an owner of a lot zoned for multifamily housing, up to five acres, subdivide it into as many as 10 parcels and build up to 10 homes through a ministerial process: no public hearing, and a decision within 60 days. SB 1123 extended the same path on July 1, 2025 to vacant lots zoned for single-family homes, up to one and a half acres. In Sonoma, Napa and Marin counties the law applies only inside incorporated cities, because its option for unincorporated land is limited to counties with more than 600,000 residents.
The law took effect July 1, 2024 and, unless extended, sunsets on January 1, 2030. It is written in two parts: Government Code section 66499.41 governs the subdivision map, and section 65852.28 governs the housing project built on the new parcels. This guide explains what qualifies, what is excluded, what a city can still require, and what it means for buying or selling a small development site in the North Bay. Other paths are covered in our guide to development rules for North Bay owners.
What SB 684 and SB 1123 allow
The two bills create one program with two kinds of eligible lots. The core limits come from Government Code 66499.41.
| Multifamily-zoned lot (SB 684) | Single-family-zoned lot (SB 1123) | |
|---|---|---|
| Maximum lot size | 5 acres | 1.5 acres |
| Lot condition | Developed or vacant, subject to tenant and affordable-housing protections | Vacant: no permanent structure unless abandoned and uninhabitable, and not housing occupied by tenants in the past five years |
| Surroundings | Substantially surrounded by qualified urban uses | Substantially surrounded by qualified urban uses |
| Maximum new parcels | 10 (a remainder parcel with existing uses doesn’t count) | 10 |
| Maximum homes | 10, not counting ADUs if the city allows them | 10, not counting ADUs if the city allows them |
| Minimum parcel size | 600 square feet, unless the city allows smaller | 1,200 square feet, unless the city allows smaller |
| Average unit size | No more than 1,750 net habitable square feet | No more than 1,750 net habitable square feet |
| Effective | July 1, 2024 | July 1, 2025 |
The project also has a density floor. If the site is in a substantially compliant housing element, it must provide at least the number of units projected for that site. Otherwise it must reach at least 66 percent of the maximum density allowed by local zoning, or 66 percent of the state default density, whichever is greater.
Homes can be owned as fee simple lots, in a common interest development, as a housing cooperative, on community land trust land, or as tenancy-in-common interests. The law does not require forming a homeowners’ association unless the Davis-Stirling Act does, although a city may require a way to maintain shared areas, such as a road maintenance agreement.
New parcels generally cannot be sold, leased or financed separately until each has a completed home, with limited exceptions for common areas and the last undeveloped parcel. A city can waive that restriction by ordinance or map condition.
Where it applies in Sonoma, Napa and Marin
Location is the first screen. The lot must be a legal parcel either in an incorporated city that includes part of an urbanized area, or in an urbanized area or urban cluster in a county with more than 600,000 residents.
None of the three North Bay counties is that large. The Census Bureau’s 2024 one-year estimates put Sonoma County at 485,375 residents, Marin at 256,400 and Napa at 132,727. A May 2025 City of Sebastopol staff memo on state housing laws put it plainly: SB 684 applies only in incorporated cities and towns in Napa and Sonoma. The same reading holds for Marin.
So a multifamily-zoned lot in Santa Rosa, Petaluma, Napa or San Rafael may qualify, while a rural parcel in unincorporated Sonoma or Napa County does not. Ask the city’s planning department to confirm that it meets the urbanized-area test.
Local implementation varies. ABAG publishes a model ordinance and an application review checklist, updated for SB 1123, that cities can adopt, and a city may adopt its own implementing ordinance without CEQA review. We have not confirmed which North Bay cities have adopted SB 684 ordinances or checklists, so ask the planning counter what it has in place before you design a project.
Sites the law excludes
Many North Bay lots fail on hazards or infrastructure rather than zoning. Under 66499.41, the lot cannot be on any of the following, subject to narrow exceptions in the statute:
- Prime farmland, farmland of statewide importance, or land protected for agriculture by a local voter-approved measure.
- Wetlands.
- A Very High Fire Hazard Severity Zone, or a High or Very High zone on the state’s map for State Responsibility Areas, with limited exceptions. This alone removes many hillside parcels; see our guide to fire hazard severity zones in the North Bay.
- A listed hazardous waste site, unless cleared.
- A delineated earthquake fault zone, unless the homes meet the applicable seismic standards.
- A special flood hazard area or regulatory floodway, unless the statute’s FEMA-related exceptions apply. Our page on North Bay flood zones explains how to check.
- Land set aside in a habitat or natural community conservation plan, habitat for protected species, or land under a conservation easement.
Two other rules matter here. Every new parcel must be served by a public water system and a municipal sewer system, which rules out septic-dependent lots. And the project cannot demolish or alter housing that is deed-restricted affordable, under rent or price control, or occupied by tenants in the past five years, or a property withdrawn from the rental market under the Ellis Act in the past 15 years.
What a city can and cannot require
A city may apply only objective zoning, subdivision and design standards, and only if they don’t conflict with the statute. Under Government Code 65852.28, it cannot:
- Apply standards that would physically prevent the project from reaching the state default density.
- Require a setback between units, except as the Building Code requires.
- Require side or rear setbacks from the original lot lines greater than four feet.
- Require more than one parking space per unit, or any parking within a half-mile walk of a high-quality transit corridor or major transit stop, or within one block of a car-share vehicle.
- Require parking to be covered or enclosed.
- Impose a floor area ratio standard below 1.0 for projects of three to seven units, or below 1.25 for projects of eight to ten units.
The city must still apply its inclusionary housing ordinance, and for some lots it may set a height limit no lower than existing zoning. It can deny a qualifying map or project only by finding, by a preponderance of the evidence, a specific adverse impact on public health and safety that cannot feasibly be mitigated.
A city does not have to allow ADUs or junior ADUs on these parcels, and it does not have to allow SB 9 urban lot splits on parcels created this way. If you are weighing a smaller project, our SB 9 lot split guide covers the two-lot alternative on single-family land.
How an SB 684 project moves from lot to permits
- Confirm the basics. City jurisdiction, zoning (multifamily, or single-family and vacant), lot size and legal parcel status.
- Screen the exclusions. Fire zone, flood zone, fault zone, farmland, habitat and easements, using the official maps and a preliminary title report.
- Check utilities. Get will-serve information for water and sewer. Without both, the lot doesn’t qualify.
- Check tenancy history. Document occupancy for the past five years and any Ellis Act withdrawal in the past 15.
- Design to the numbers. Hit the density floor while keeping the average unit at or under 1,750 net habitable square feet.
- Meet with planning. Ask whether the city uses an implementing ordinance or checklist and which objective standards it will apply.
- File complete applications. The parcel map or tentative map and the housing project are each reviewed ministerially, and the city must approve or deny a complete application within 60 days or it is deemed approved. A denial must list the deficiencies and how to fix them.
- Record the final map and pull building permits. Plan for impact fees, utility connection charges and the separate-sale restriction until homes are complete.
HCD’s April 2026 fact sheet states that qualifying projects are exempt from CEQA review. For the wider sequence of entitlements in this region, see our land entitlement guide for Sonoma County.
What it means for land value
SB 684 can add value to a small city lot, but only when the site clears every screen. A multifamily-zoned lot with sewer and water, no fire or flood exclusion and no recent tenants has a clearer path than it did before 2024. A lot that fails one test is worth what its existing zoning supports.
The density floor and the 1,750-square-foot average work against large luxury homes and toward smaller for-sale units, so a buyer’s numbers should reflect that product. Fees, construction cost, the separate-sale restriction and local inclusionary rules all affect feasibility.
Price a lot on what has been confirmed with the city, not on the statute alone. HCD’s guidance on edge cases, such as a 2025 technical assistance letter suggesting a single-family lot with an existing home might qualify by placing the home on a remainder parcel, is advisory and may not be followed by every city or court. Compare other paths too: ADUs on multifamily property, builder’s remedy projects, or a traditional subdivision as described in our guide to subdividing land in Sonoma and Napa.
Selling a lot with SB 684 potential
If your lot may qualify, a buyer will pay more attention when you can show the facts instead of the possibility. Assemble:
- The zoning and general plan designation, with any notes from a planning counter meeting.
- Fire, flood and fault zone printouts from the official maps.
- Water and sewer availability information.
- A survey or at least the recorded parcel map, plus a preliminary title report showing easements.
- Tenancy history if the lot has or had rental housing.
Our guide to building lots and ADUs in Sonoma County covers other lot questions buyers ask.
Questions people ask
What is SB 684 in California?
SB 684 (2023), the Starter Home Revitalization Act, requires cities to approve qualifying subdivisions of up to 10 parcels and projects of up to 10 homes on multifamily-zoned lots of five acres or less ministerially, without a hearing, within 60 days. It took effect July 1, 2024.
What did SB 1123 change?
Effective July 1, 2025, SB 1123 extended the program to vacant lots zoned for single-family homes of up to 1.5 acres, with a 1,200-square-foot minimum parcel size. ADUs, where a city allows them, don’t count toward the 10-unit limit.
Does SB 684 apply in unincorporated Sonoma or Napa County?
No. Unincorporated land qualifies only in counties with more than 600,000 residents, and Sonoma, Napa and Marin are all smaller. The law can apply inside incorporated cities in those counties.
Can I use SB 684 on a lot with a septic system?
No. Each new parcel must be served by a public water system and a municipal sewer system.
Can I build large homes under SB 684?
Not on average. The average floor area of the units can’t exceed 1,750 net habitable square feet, not counting garages and unfinished space, and the project must meet a minimum density.
Do I have to form an HOA?
Not unless the Davis-Stirling Act requires one for the ownership structure you choose. A city may still require a way to maintain shared areas, such as a road maintenance agreement.
How long does approval take?
The city must approve or deny a complete application within 60 days, or it is deemed approved. Final maps, building permits and construction take longer.
Does SB 684 expire?
Yes. Both code sections are scheduled to be repealed on January 1, 2030 unless the Legislature extends them.
If you own or are considering a small development site in a North Bay city, we can help you gather the zoning, hazard and utility facts and market the lot to builders. Start on our investors page. This is general information, not legal advice; talk to a California land use attorney and a civil engineer about your site.
Sources & notes
- California Public Law: Government Code section 66499.41
- California Public Law: Government Code section 65852.28
- California Public Law: Government Code section 65852.21
- California HCD: Starter Home Revitalization Act fact sheet (April 2026)
- ABAG: SB 684 and SB 1123 small lot subdivision model ordinance and checklist
- County of San Mateo Planning: SB 684 and SB 1123 small lot subdivision and housing development
- City of Sebastopol: Housing laws refresher staff memo (May 2025)
- Census Reporter (ACS 2024 one-year): Sonoma County
- Census Reporter (ACS 2024 one-year): Marin County
- Census Reporter (ACS 2024 one-year): Napa County
- Cox, Castle & Nicholson: HCD guidance clarifies SB 1123’s reach (November 2025)
Last reviewed October 2026 by Matthew Martinez.
