SB9 in San Diego: City Lot Split and Development Guide

Quick Answer

The City of San Diego implements SB9 through two related paths: a Multi-Dwelling Unit Development for additional primary dwelling units and an Urban Lot Split for a two-lot subdivision.

The City's February 2026 Information Bulletin 409 explains that qualifying projects can use either path or combine them. It also explains why sequencing matters: building first can place a structure where it later blocks subdivision requirements. The City identifies a combined unit-and-lot-split application as the preferred option when the owner intends to pursue both.

That does not mean every San Diego property should use SB9. Zoning, lot geometry, frontage, coastal review, access, utilities, easements, existing structures, fire and stormwater issues, and the owner's end goal still decide whether the project is practical.

San Diego's Two SB9 Paths

The City uses local terms for the two main SB9 options:

• Multi-Dwelling Unit Development, or MDUD: development resulting in no more than two dwelling units on one lot, including existing and new structures.
• Urban Lot Split, or ULS: a subdivision that divides one existing premise into no more than two separately conveyable lots.

A property owner may pursue units, a lot split, or both. The City caps the total number of dwelling units across the two resulting lots at four under the SB9 framework described in Information Bulletin 409.

Which San Diego Zones May Qualify

Information Bulletin 409 states that the City's MDUD and Urban Lot Split rules apply in zones that allow single-dwelling development but not multiple-dwelling development. It identifies RS, RE, RX, and RT zones, plus qualifying Planned District zones.

The zone name is not the entire answer. A property should also be screened for statewide exclusions, protected housing and tenant rules, historic or environmental constraints, prior SB9 activity, and local overlay or planned-district requirements.

Use the City's current zoning and parcel information tools, then confirm the result against the current code and Development Services guidance.

San Diego Urban Lot Split Requirements

The City describes the Urban Lot Split as a Process One, ministerial Parcel Map. The official bulletin states that:

• The two lots must be approximately equal in size.
• Neither lot may be smaller than 40 percent of the original lot area.
• Each new lot must be at least 1,200 square feet.
• Base-zone rules for floor area ratio, street frontage, driveway width, and other standards apply when feasible.
• An access easement must be recorded when a resulting lot cannot meet base-zone street-frontage or driveway-width requirements.
• Residential use is required on lots created through the Urban Lot Split.
• Rental periods must be at least 31 days.

The record owner must also complete the City's current owner-occupancy affidavit before recordation, subject to the exceptions stated in law and the City's forms.

Parcel Map And Development Package

An Urban Lot Split is not only a line drawn across an aerial image. The City requires a Parcel Map application and a development-plan package that gives reviewers enough information to evaluate the future building layout and code compliance.

The application can require site and map information showing the proposed parcels, building footprints, square footage, access, frontage, driveways, easements, utilities, and other subdivision details. Improvements or modifications needed for right of way, water, sewer, stormwater, fire suppression, or other issues may need to be resolved before the Parcel Map can be recorded.

This is why an early feasibility plan should connect the proposed split with a realistic future development layout.

Why Project Sequencing Matters

The City's bulletin warns that constructing units or ADUs before planning the lot split can limit or eliminate a future Urban Lot Split. A building may occupy the only practical split line, interfere with frontage or driveway requirements, or create a unit mix that no longer fits the later subdivision strategy.

If the long-term goal includes a separate parcel, review the lot-split geometry before placing new units. San Diego identifies a combined MDUD and Urban Lot Split application as the preferred path when both are intended.

That sequencing decision should be made with the property owner, engineer, designer, lender, title professional, and other appropriate advisors. No financing, tax, sale, rental, value, approval, or development outcome is guaranteed.

Coastal Overlay Zone Review

San Diego's Coastal Overlay Zone can change the approval path. Information Bulletin 409 states that properties in the Coastal Overlay Zone are subject to the City's Coastal Development Permit procedures.

Coastal properties can also involve parking, sea-level-rise, access, bluff, geology, drainage, or Local Coastal Program issues. The exact review depends on the property and current City rules. A general SB9 screen should not be used as a substitute for parcel-specific coastal review.

Parking And Beach-Area Issues

The City's current bulletin distinguishes parking based on location and project type. It notes Transit Priority Area exceptions and additional parking requirements in the Beach Impact Area unless the City accepts the applicable shared-vehicle condition.

Parking is only one site-design issue. Narrow coastal lots may also have limited driveway space, constrained access, existing buildings close to lot lines, and costly utility or drainage routes. Those physical conditions should be tested with the proposed parcel layout.

Access, Utilities, Drainage, And Fire

San Diego's bulletin specifically identifies right-of-way, water, sewer, stormwater, and fire-suppression issues that may need to be addressed before recordation.

Before a homeowner commits to a split, the property should be checked for:

• A workable split line around existing and proposed structures.
• Street frontage, driveway width, and a legally supportable access easement if needed.
• Water and sewer routing to both parcels.
• Utility easements and conflicts.
• Stormwater, drainage, slope, retaining-wall, and grading conditions.
• Fire access and fire-suppression requirements.
• Whether the resulting parcels still support useful building envelopes.

A project can meet the 40/60 area test and still fail the practical layout test.

SB9 Versus An ADU In San Diego

An ADU may be simpler when the owner wants rental income or family housing on the same legal parcel. An Urban Lot Split may be more useful when a separate legal parcel supports the owner's long-term resale, estate, family, financing, or development strategy.

Because early unit placement can affect later subdivision potential, the comparison should happen before design work is locked in.

Helpful next reads:

• What is SB9?
• SB9 vs ADU
• SB9 lot split cost
• SB9 lot size requirements and the 40 percent rule
• The step-by-step SB9 lot split process

Step-By-Step San Diego Review

1. Confirm that the property is inside the City of San Diego rather than an unincorporated County area or another city.
2. Check the base zone and any Planned District or overlay rules.
3. Review statewide SB9 eligibility, protected housing, tenant, historic, environmental, and prior-split restrictions.
4. Test lot area, the 40/60 split, frontage, driveway width, existing structures, and future building envelopes.
5. Review coastal, beach, parking, fire, slope, grading, drainage, and stormwater conditions.
6. Plan access easements, water, sewer, power, and other utility service.
7. Decide whether to pursue units, an Urban Lot Split, both concurrently, an ADU, or no project.
8. Prepare the current City Parcel Map, development-plan, declaration, and supporting application materials only after feasibility looks strong.
9. Resolve agency comments and any required right-of-way, utility, stormwater, fire, or mapping issues before recordation.

Start With A San Diego Property Review

A useful SB9 answer starts with the address, zoning, parcel geometry, access, utilities, overlays, and the owner's goal. The review should happen before architecture or unit placement makes the subdivision harder.

Properties outside the City of San Diego may follow a different process. Use the San Diego County SB9 guide for unincorporated properties, or browse the California SB9 city guide hub for other jurisdictions.

Start with the SB9 eligibility checker and include the San Diego property address and any planned ADU or construction work.

Frequently Asked Questions

What San Diego zones may allow an SB9 lot split?

The City's February 2026 bulletin identifies qualifying RS, RE, RX, and RT zones, plus Planned District zones that permit single-dwelling but not multiple-dwelling development. Other statewide and local eligibility limits still apply.

Does each new San Diego parcel have to be 1,200 square feet?

The City's current Urban Lot Split guidance says each new parcel must be at least 1,200 square feet and neither parcel may be smaller than 40 percent of the original parcel area.

Can I build an ADU first and split the property later?

Possibly, but the City warns that earlier units can prevent a future Urban Lot Split by blocking subdivision standards or changing the allowed unit strategy. Review the split before placing new construction if a separate parcel is part of the long-term goal.

Does a coastal San Diego property need a Coastal Development Permit?

Information Bulletin 409 says properties in the Coastal Overlay Zone are subject to the City's Coastal Development Permit procedures. Parcel-specific coastal, parking, access, sea-level-rise, bluff, and other constraints may also need review.

Is the San Diego Urban Lot Split automatic if the parcel meets the 40/60 rule?

No. The project must satisfy applicable eligibility rules and produce a workable parcel map, access, utility, drainage, fire, and future development strategy. The area test alone does not prove feasibility.

Official Sources

Statewide:

• California Government Code Section 65852.21
• California Government Code Section 66411.7
• California HCD SB9 Fact Sheet
• California HCD SB9 Implementation Guidance

City of San Diego:

• City of San Diego Information Bulletin 409: Multi-Dwelling Unit Developments and Urban Lot Splits
• City of San Diego Housing Affordability Toolkit
• San Diego Municipal Code Chapter 13: Zones
• City of San Diego Land Development Code Updates
• City of San Diego Development Services Application Portal

Sources last reviewed: July 11, 2026.