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Is Your California Lot Eligible for SB 9, an ADU or SB 684? Eleven Checks

Three state laws let a California lot hold more homes: SB 9 (2021), which allows two homes and a lot split in single-family zones; state ADU law, which allows accessory dwelling units (ADUs, smaller extra homes on the same lot); and SB 684 and SB 1123, which allow up to 10 small lots. Each law has its own list of lots it leaves out. This page runs your lot through eleven checks, side by side, so you know which law you can use before you pay for plans.

The Eleven Checks at a Glance

Read across each row. A lot can fail SB 9 and still qualify for ADUs, because ADU law has the shortest list of exclusions. City building and safety rules apply to every project, whichever law you use.

Sources: Gov. Code 65852.21, 66411.7, 66499.41, HCD SB 9 Fact Sheet and HCD ADU Handbook.

Check 1: Your Zone

Zoning is the first check. SB 9 (2021) covers only a single-family residential zone. The California Department of Housing and Community Development (HCD) says in its SB 9 Fact Sheet that parcels in multifamily, commercial, agricultural and mixed-use zones are not covered "even if they allow single-family residential uses as a permitted use."

Some cities have several single-family zones. HCD tells them to look at each zone's purpose, and says that "minimum lot sizes, natural features such as hillsides, or the permissibility of keeping horses should not factor into the determination." A large-lot or hillside zone that exists for single-family homes is still a single-family zone for SB 9.

ADU law reaches further. It applies on lots with an existing or proposed house and on lots with a multifamily building. SB 684 covers the opposite group from SB 9: lots zoned for multifamily homes of up to five acres, plus, since SB 1123, vacant single-family lots of up to one and one-half acres.

Check 2: Urban Area

SB 9 applies in a city whose boundaries include some part of an urbanized area or urban cluster as the US Census Bureau draws them, under Government Code 65852.21(a)(1). On unincorporated county land, the parcel must sit wholly inside such an area. SB 684 uses a similar test: an incorporated city with part of an urbanized area, or an urbanized area or urban cluster in a county with more than 600,000 people. If your lot is in a small town or on county land, ask the planning department whether it meets the test.

Check 3: Lot Size

An SB 9 lot split must create two lots that each measure at least 1,200 square feet, and neither lot may be smaller than 40 percent of the original, under Government Code 66411.7. A city may adopt a smaller minimum by ordinance. At the state default, the original lot needs at least 2,400 square feet. On a 5,000 square foot lot, the smaller of the two new lots must be at least 2,000 square feet.

SB 684 sets smaller minimums: each new parcel at least 600 square feet, or 1,200 square feet if it is zoned for single-family use, unless the city goes lower. The starting lot also has upper limits: five acres for a multifamily-zoned lot and one and one-half acres for a vacant single-family lot. Those numbers change on January 1, 2027, when SB 1116 lowers the minimum parcel size to 480 or 960 square feet. The SB 684 page has the details.

Check 4: Fire Hazard Severity Zones

SB 9 takes its site exclusions from Government Code 65913.4(a)(6) as that list read on September 16, 2021, and HCD names fire hazard areas among the conditions that can disqualify a project. SB 684 excludes very high fire hazard severity zones in its own text, plus high and very high zones on the state's own fire maps for State Responsibility Areas.

The maps changed in 2025. The Office of the State Fire Marshal at CAL FIRE (the California Department of Forestry and Fire Protection) released new recommended maps for Local Responsibility Areas, the maps cities and counties adopt by ordinance, starting in February 2025, and issued Los Angeles County's on March 24, 2025. A city must adopt the recommended zones by ordinance within 120 days. It may add zones or raise their level, and it may not lower them. A lot outside a zone in 2024 may sit inside one now, so check the current map.

ADUs are treated differently. HCD's ADU Handbook says "the presence of a High Fire Hazard Severity Zone is not a conclusive rationale to warrant restricting ADUs." Homes in high and very high zones may still have to meet California Building Code Chapter 7A, the wildfire building rules, and the defensible space rules in Public Resources Code 4291.

Checks 5 to 7: Flood, Earthquake and Natural Land

SB 9 and SB 684 share these environmental exclusions. A lot in a FEMA flood zone or regulatory floodway (the high-risk areas mapped by the Federal Emergency Management Agency) is excluded unless it meets the federal flood program's rules. A lot in an earthquake fault zone is excluded unless the homes are built to the seismic code. Prime farmland, wetlands, protected species habitat, land under a conservation plan and land under a conservation easement are excluded.

HCD lists the SB 9 conditions in plain words: "farmland, wetlands, fire hazard areas, earthquake hazard areas, flood risk areas, conservation areas, wildlife habitat areas, or conservation easements." SB 684's own list also names listed hazardous waste sites, and it requires public water and municipal sewer service.

Check 8: Historic Status

AB 1061 (Chapter 505, Statutes of 2025) rewrote the SB 9 historic limits, effective January 1, 2026. For two homes on one lot, SB 9 now excludes a contributing structure in a historic district on the State Historic Resources Inventory, and any parcel individually listed as a historic resource or as a city or county landmark. For a lot split, it excludes a landmark property and any split that would demolish or alter a contributing structure, or an existing exterior structural wall, in a historic district. Cities may adopt written standards to protect a district listed in the California Register of Historical Resources.

The SB 684 site list in Government Code 66499.41(a)(9) has no historic category. For ADUs, a lot in an architecturally and historically significant historic district is one of the cases where the city may require no parking for the ADU.

Check 9: Tenants, Rent Control and the Ellis Act

SB 9 cannot demolish or alter housing that is rent-restricted by a recorded covenant, under rent or price control, or "occupied by a tenant in the last three years." SB 684 uses five years. The rule follows the housing: a tenant who lived there under the previous owner counts.

The Ellis Act, Government Code 7060, lets an owner take rental units off the market. If any owner used it on the parcel within the 15 years before your application, SB 9 and SB 684 are both unavailable. ADU law has no tenant-history test, so an ADU remains possible on a lot that fails this check. The rent and tenant rules page covers the rent cap and eviction rules that apply once homes are built.

Check 10: Coastal Zone

The California Coastal Act still applies to SB 9 projects inside the coastal zone, so you may need a coastal development permit. Under Government Code 65852.21(k), the city does not have to hold a public hearing on that permit for an SB 9 project. For ADUs, HCD's handbook says a coastal permit application must be decided within 60 days. The SB 684 text does not mention the Coastal Act, so ask the city how it handles coastal permits for a small-lot subdivision.

Check 11: Past Lot Splits

A parcel can be split only once under SB 9. HCD's fact sheet says it plainly: "A parcel may only be subdivided once under Government Code section 66411.7." An owner who already split an adjacent parcel under SB 9, or anyone acting with that owner, cannot split this one. SB 684 has a matching rule: a lot created by SB 9 or SB 684 cannot use SB 684, and a parcel created under SB 684 cannot use an SB 9 split.

Two More Questions: Transit and Charter Cities

Distance to transit changes what you can build. Near a high-quality transit corridor or major transit stop, SB 9 and ADU projects need no parking, and an ADU may reach 18 feet. HCD's handbook points owners to the California State Geoportal map to check whether an address is within a high-quality transit corridor. In seven counties, land within a half mile of a qualifying rail or bus stop also falls under SB 79, which allows buildings of five or more homes. The SB 79 page explains the maps.

Five charter cities (Redondo Beach, Carson, Torrance, Whittier and Del Mar) won a 2024 trial court judgment that stopped the state from enforcing SB 9 against them. The Court of Appeal reversed that judgment on November 12, 2025 and sent the case back to the trial court. If your lot is in one of those five cities, ask the planning department whether it is accepting SB 9 applications today.

Where to Go Next

Also see VanPlex's California SB 9 comparison page and the California multiplex guide overview.

Frequently Asked Questions

Official sources (checked October 2026)