California SB9 City Guides: Lot Split Rules by City and County

Quick Answer

California SB9 is statewide, but SB9 eligibility is never just a statewide question.

State law may create a path for a qualifying single-family property to add primary residential units, split one lot into two legal parcels, or combine both paths. The real answer depends on the local city or county, the property’s zoning, lot geometry, overlays, access, utilities, easements, fire/public works issues, and whether the parcel can support a practical map and building strategy.

That is why these Riechers Engineering city guides start with one practical question:

Can this specific property actually work under SB9 before the owner spends money on plans, surveys, applications, and city fees?

Why Local SB9 Guides Matter

SB9 is not the same experience in every city.

The broad statewide rules explain what SB9 may allow. Local city and county pages explain what homeowners need to check in a specific jurisdiction before assuming the project is realistic.

A useful SB9 city guide should not be the same generic article with a different city name. It should help a homeowner understand:

• Whether the city has local SB9 forms, checklists, objective standards, or implementation memos.
• Whether the local process is handled by a city or by the county.
• Which zoning, lot-size, access, utility, coastal, hillside, historic, fire, drainage, or public works issues may matter.
• Whether a parcel-specific engineering review is needed before moving forward.

How Riechers Looks At SB9

Most homeowners start with the law. Riechers starts with the parcel.

That means a local SB9 review should look at both sides of the question:

• The legal path: zoning, statewide SB9 eligibility, city standards, application rules, tenant protections, exclusions, and objective requirements.
• The engineering path: lot geometry, access, utilities, easements, existing structures, grading, drainage, fire access, public works, parcel-map feasibility, and whether the result creates useful value.

If the law says “maybe” but the parcel layout, utility routing, or access path does not work, the owner can waste money quickly. These guides are designed to help homeowners screen the risk earlier.

What SB9 May Allow Statewide

For an eligible California property, SB9 can create two primary paths:

• Two-unit development on a qualifying single-family residential parcel.
• An urban lot split that divides one qualifying parcel into two legal parcels.

When both paths work together, a property may support additional primary residential units across two resulting parcels. That is the opportunity homeowners hear about, but it is not automatic.

SB9 does not erase all local standards, utility problems, hazard constraints, tenant protections, mapping requirements, or site design issues. It creates a ministerial path for qualifying projects that still have to satisfy applicable objective standards and practical feasibility.

Statewide SB9 Rules To Understand First

Before a homeowner compares city rules, it helps to understand the statewide SB9 framework that every local review starts from.

The statewide review usually includes:

• Single-family residential zoning.
• Urbanized-area or urban-cluster status.
• Protected housing and tenant restrictions.
• Historic, environmental, fire, flood, earthquake, farmland, conservation, and other exclusion issues.
• Ministerial review and objective standards.
• The 40/60 split concept for urban lot splits.
• Minimum parcel-size rules.
• Owner-occupancy affidavit requirements for urban lot splits.
• Short-term rental restrictions.
• Parking limitations and exceptions.
• The difference between a two-unit development and an urban lot split.

Why The Parcel Decides The Answer

The law can say a project may be possible. The property still has to make sense.

Riechers should frame every local guide through an engineering feasibility lens:

• Is there a practical split line?
• Can both parcels access a public right of way?
• Are utilities available or reasonably extendable?
• Do easements, existing structures, or setbacks block the layout?
• Do drainage, grading, slope, fire, coastal, or geologic constraints make the project expensive or risky?
• Would the split create useful property value after survey, mapping, engineering, city review, recordation, and future development costs?

That is the difference between a generic SB9 article and a useful property strategy.

Published Local SB9 Guides

Start with the local guide that matches the property location:

• Los Angeles County SB9 guide for unincorporated Los Angeles County properties and county-level SB9 review issues.
• Los Angeles SB9 guide for properties inside the City of Los Angeles, including ZIMAS, overlays, hillside/fire concerns, historic flags, and city-specific application issues.
• Alhambra SB9 guide for San Gabriel Valley lots, older residential neighborhoods, lot geometry, access, utilities, and city objective standards.
• Hermosa Beach SB9 guide for coastal-zone, small-lot, parking, access, and Local Coastal Plan issues.

If the property is not in one of these cities, the same screening logic still applies. The first step is to confirm whether the property is inside an incorporated city, in an unincorporated county area, or subject to special local standards. From there, the property still needs a parcel-specific feasibility review.

How SB9 Compares With ADUs And Additions

SB9 is not always the best path.

An ADU can be simpler when the owner wants rental income or family housing on the same legal parcel. A home addition can be better when the owner needs more living space but does not need a separate parcel. SB9 becomes more interesting when the goal is separate parcel potential, resale flexibility, estate planning, financing optionality, or long-term property value.

The right choice depends on the property and the owner’s goal. That is why Riechers compares SB9, ADUs, additions, and no-project options before pushing a homeowner into an expensive application path.

Helpful next reads:

• What is SB9?
• SB9 vs ADU
• SB9 lot split cost
• SB9 lot size requirements and the 40 percent rule
• Can you do an SB9 lot split with a mortgage?

Start With A Feasibility Review

Before spending money on architecture, plans, survey work, city fees, or a parcel-map application, the property should be screened for zoning, lot geometry, access, utilities, easements, hazards, drainage, public works, and likely value after cost.

Start with the SB9 eligibility checker so the property can be reviewed before the owner goes too far down the wrong path.

Frequently Asked Questions

Is SB9 the same in every California city?

No. SB9 is a statewide law, but each city or county may apply objective standards, application procedures, public works requirements, zoning tools, and local implementation rules. The parcel still has to be reviewed for site-specific feasibility.

Why should I check my city before applying for SB9?

City rules, overlays, utilities, access, fire standards, coastal issues, historic districts, lot dimensions, and existing building placement can change whether a property is a realistic SB9 candidate.

Does a city guide mean my property qualifies?

No. A city guide helps explain the local review issues. The actual answer requires a parcel-specific review of zoning, lot geometry, access, utilities, easements, hazards, and project goals.

Should I start with architecture or feasibility?

Start with feasibility. A property should be screened before spending money on full architectural plans, surveys, applications, or city fees.

Where should I start if my city is not listed yet?

Start with the statewide SB9 guide and then check the property through the eligibility checker. Riechers can still review zoning, lot geometry, access, utilities, easements, hazards, and local constraints even when a dedicated city guide is not live yet.

Official Sources

Statewide:

• California Government Code Section 65852.21: https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=65852.21
• California Government Code Section 66411.7: https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66411.7
• California HCD SB9 Fact Sheet: https://www.hcd.ca.gov/sites/default/files/docs/planning-and-community/sb-9-fact-sheet.pdf
• California HCD SB9 Implementation Guidance: https://www.hcd.ca.gov/sites/default/files/docs/planning-and-community/lot-splits-and-duplexes-sb-9.pdf
• SB450 bill page: https://leginfo.legislature.ca.gov/faces/billNavClient.xhtml?bill_id=202320240SB450
• SCAG SB9 Implementation Resource: https://scag.ca.gov/sites/default/files/2024-05/senate_bill_9_-_ministerial_approval_of_duplexes_and_urban_lot_splits.pdf