SB9 in Los Angeles County: Lot Split and Two-Unit Development Guide

Quick Answer

SB9 may allow a qualifying Los Angeles County homeowner to add up to two main dwelling units on a single-family residential parcel, split a qualifying lot into two parcels, or combine both paths when the property, zoning, hazards, access, utilities, and parcel-map requirements support it.

But Los Angeles County is not one simple SB9 market. Unincorporated county properties, coastal areas, hillside lots, fire zones, older neighborhoods, private sewer systems, easements, and incorporated cities can all change the answer.

The safest first step is not architecture. It is a property-specific SB9 feasibility review.

What SB9 May Allow

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

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

If both paths work, the result may be more flexible than a normal ADU strategy because an SB9 lot split can create a separate legal parcel. That separate-parcel question is why homeowners should compare SB9 against ADUs, additions, and normal development before spending heavily.

Statewide SB9 Rules

California SB9 is built around ministerial review for qualifying projects, meaning the review is based on objective standards rather than a discretionary public-hearing process.

At the statewide level, the review should account for:

• Whether the property is in a qualifying single-family residential zone.
• Whether the property is in an urbanized area or urban cluster.
• Whether tenant protections, protected housing rules, historic resources, environmental constraints, or hazard constraints apply.
• Whether an urban lot split can satisfy the general 40/60 split requirement.
• Whether each new parcel can meet the minimum parcel-size requirement.
• Whether the owner-occupancy affidavit applies for an urban lot split.
• Whether short-term rental restrictions apply.
• Whether objective local standards can be applied without physically preventing qualifying SB9 units.

Los Angeles County-Specific Implementation

Los Angeles County Planning describes SB9 as allowing up to two units on a single-family zoned lot and also allowing an urban lot split of a single-family zoned lot when the property qualifies.

For unincorporated Los Angeles County, the county’s SB9 materials and 2025 implementation memo are important because they address county-specific project types, required forms, locational criteria, excluded areas, development standards, and application requirements.

Important county-specific review items include:

• Whether the site is in a county zone that can use the SB9 path.
• Whether the parcel is in an urbanized area or urban cluster.
• Whether the site is affected by coastal, wetland, historic, farmland, fire, earthquake, flood, conservation, or other hazard constraints.
• Whether the proposal is a two-unit development, an urban lot split, or both.
• Whether the urban lot split requires a parcel map before later development can proceed.
• Whether private sewer or onsite wastewater clearance is needed.
• Whether required county application materials are complete.

Los Angeles County’s application materials reference SB9-specific forms including applicant acknowledgement, owner-occupancy affidavit, pre-existing site conditions certification, subdivision checklist, financial responsibility forms, disclosure affidavits, easement affidavits, and related documents where applicable.

Incorporated Cities Are Different

A Los Angeles County page should not pretend every property in the county follows the same local process.

Unincorporated county parcels are reviewed through Los Angeles County processes. Incorporated cities such as Los Angeles, Alhambra, Pasadena, Glendale, Burbank, Long Beach, Santa Monica, Redondo Beach, Manhattan Beach, Torrance, and Hermosa Beach can have their own objective standards, applications, zoning tools, public works requirements, and local SB450 updates.

That is why this county hub points homeowners into live city-specific guides where the local process is different:

• SB9 in Los Angeles
• SB9 in Alhambra
• SB9 in Hermosa Beach
• California SB9 City Guides

Engineering Constraints That Can Make Or Break The Project

For Los Angeles County SB9 projects, the legal question and the engineering question are not the same thing.

Common Los Angeles County SB9 deal-killers include:

• A house placed in the middle of the lot, leaving no practical split line.
• Narrow frontage or no clean access to both future parcels.
• Hillside, slope, geologic, fire, flood, or drainage constraints.
• Coastal or environmental overlays.
• Historic-resource issues.
• Easements that block development or utility routing.
• Existing utility lines that make a clean split expensive.
• Private sewer or septic constraints.
• Awkward 40/60 parcel geometry.
• Shared driveways, private roads, or access conditions.
• A split that technically works but does not create enough value after survey, mapping, engineering, fees, and construction costs.

This is where Riechers can be stronger than a generic SB9 blog. The real answer is whether the parcel can support a useful, recordable, buildable strategy.

Owner-Occupancy, Renting, And Selling Questions

Los Angeles County homeowners often ask whether they can rent, sell, or hold the new parcel after an SB9 lot split. The answer depends on the project type, state law, county requirements, and the owner’s long-term plan.

For an urban lot split, state law includes an owner-occupancy affidavit requirement and short-term rental restrictions. A homeowner should also think through title, financing, easements, utilities, and how the resulting parcels would function after the map is recorded.

That is why the review should not stop at “can the application be submitted?” The better question is whether the recorded parcels would be useful, marketable, financeable, and aligned with the owner’s goal.

SB9 vs ADU vs Addition

An ADU may be the simpler path when the owner wants rental income or family housing on the same parcel.

SB9 may be more useful when the owner wants a separate legal parcel, potential resale flexibility, estate-planning flexibility, financing optionality, or a stronger long-term property-value play.

An addition may make sense when subdivision and new utility/access work would be too expensive or when the owner wants to keep the property simple.

The right strategy depends on the parcel, the owner’s goal, and the cost/risk profile.

Step-by-Step Los Angeles County SB9 Review

1. Confirm whether the property is in unincorporated Los Angeles County or inside an incorporated city.
2. Confirm zoning and urbanized-area status.
3. Check statewide SB9 exclusions and local county restrictions.
4. Review lot size, lot shape, frontage, and the potential 40/60 split.
5. Check existing structures and possible split lines.
6. Review access, driveways, easements, and public right-of-way issues.
7. Review sewer, water, utility, drainage, grading, and fire/public works constraints.
8. Decide whether SB9, ADU, addition, or no project is the better strategy.
9. Prepare the required survey, site plan, parcel map, forms, and application materials only after feasibility looks strong.
10. Submit, respond to corrections, record the parcel map if approved, and then move into later permit steps as needed.

Related SB9 Guides

If the property is inside an incorporated city, start with the city page instead of relying only on the county overview.

• Los Angeles SB9 lot split guide
• Alhambra SB9 lot split guide
• Hermosa Beach SB9 lot split guide
• What is SB9?
• SB9 lot size requirements and the 40 percent rule
• SB9 vs ADU
• Check SB9 eligibility

Frequently Asked Questions

Does SB9 work everywhere in Los Angeles County?

No. SB9 is a statewide law, but eligibility depends on zoning, location, protected housing rules, hazard constraints, objective local standards, and property-specific engineering feasibility. Incorporated cities can also have their own processes and objective standards.

Is an SB9 lot split the same as an ADU?

No. An ADU usually adds a unit on the same legal parcel. An SB9 urban lot split may create two separate legal parcels if the property qualifies. That separate-parcel issue can affect resale, financing, estate planning, and long-term property strategy.

Can I split my Los Angeles County lot into two equal parcels?

Maybe. California SB9 generally requires an urban lot split to create two parcels where neither parcel is less than 40 percent of the original lot area, and each new parcel generally must be at least 1,200 square feet unless a local rule allows otherwise. The geometry also has to work in the real world.

Can a property in a fire, coastal, hillside, or flood area qualify?

Those constraints can create serious problems and may make SB9 unavailable or impractical depending on the specific property and applicable rules. The property should be checked against official maps, local standards, and engineering constraints before moving forward.

What is the safest first step?

Start with a feasibility review. Riechers should check zoning, local standards, lot geometry, access, utilities, easements, drainage, hazards, and parcel-map feasibility before the owner spends money on full plans or applications.

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

Los Angeles County:

• LA County Planning SB9 page: https://planning.lacounty.gov/planning-permits/sb-9/
• LA County Applications and Forms: https://planning.lacounty.gov/applications-and-forms/
• LA County SB9 application portal/info page: https://case.planning.lacounty.gov/view/sb_9
• LA County SB9/SB450 implementation memo updated August 18, 2025: https://planning.lacounty.gov/wp-content/uploads/2025/08/2025_SB9_Memo_EO_N3225_final-rev-TF-2025.08.18.ajb_.pdf