SB9 in San Francisco: Lot Split Rules and Property Feasibility

Quick Answer

Some San Francisco properties may still qualify for an SB9 two-unit development, an urban lot split, or a combination of both. The current San Francisco Planning guidance identifies RH-1, RH-1(D), and RH-1(S) parcels as the starting zoning categories for SB9 review.

The zoning question must be checked against the property today. San Francisco's Family Zoning Plan took effect on January 12, 2026 and changed zoning across substantial portions of the City. Old zoning reports, neighborhood assumptions, and articles written before that date may no longer describe a parcel correctly. SF Planning's Bulletin No. 8 was updated on June 24, 2026 and still directs applicants to screen current RH-1 zoning through the City's Property Information Map.

Zoning is only the first gate. A workable San Francisco lot split also depends on lot size, tenant and rent-control history, historic status, existing buildings, a functional split line, access, utilities, easements, objective design standards, Public Works mapping, and the owner's intended use of the resulting parcels.

Check Current Zoning After The Family Zoning Plan

Start with the SF Planning Property Information Map, often called PIM. Search by street address or block and lot, then review the current zoning, height and bulk district, special-use districts, historic information, environmental information, planning applications, building permits, and recorded notices shown for the parcel.

This current-property check matters because the Family Zoning Plan changed the Planning Code and Zoning Map in 2026. A property that was historically described as RH-1 may now have a different zoning profile, while some parcels remain in RH districts. The City's current SB9 guidance, not an old real-estate listing or archived map, should control the initial screen.

PIM is a strong research tool, but it is not a substitute for a complete title, survey, code, and agency review. Records can identify likely constraints without proving that a specific split design will be approved.

Which San Francisco Zones May Qualify

SF Planning's current Bulletin No. 8 and SB9 application materials identify RH-1, RH-1(D), and RH-1(S) as the applicable single-family zoning districts. A parcel in one of those districts must still satisfy the state location and housing-protection rules.

Common eligibility questions include:

• Was any housing on the site occupied by a tenant during the relevant three-year period?
• Is an existing unit subject to rent or price controls?
• Is the property or a contributing structure in a protected historic resource or district?
• Is the parcel affected by a state exclusion involving hazards, protected lands, or other location criteria?
• Was the parcel created through a prior SB9 urban lot split?
• Has the owner, or someone acting in concert with the owner, used SB9 to split an adjacent parcel?

San Francisco also requires supporting occupancy information with the application. These protections need to be checked before an owner relies on the lot's dimensions or begins a full design.

San Francisco Lot Size And 40/60 Rules

The City's current guidance describes the core urban-lot-split math:

• The original parcel must be at least 2,400 square feet.
• The split creates no more than two parcels.
• Each resulting parcel must be at least 1,200 square feet.
• Neither new parcel may be smaller than 40 percent or larger than 60 percent of the original lot area.
• The parcel cannot be split a second time through SB9.
• An owner cannot use a coordinated series of adjacent SB9 lot splits in violation of the state rule.

Passing the area test does not establish feasibility. Many San Francisco lots are narrow, deep, sloped, heavily improved, or constrained by existing buildings and rear-yard conditions. The proposed parcels still need useful dimensions, legal access, utility service, compliant building areas, and a map that can be recorded.

For a deeper explanation, review the SB9 lot size requirements and 40 percent rule.

Lot Split, Duplex, Or A Combination

SF Planning describes three SB9 paths:

1. A lot split without a housing project in the same application sequence.
2. A two-unit housing development without a lot split.
3. A combined lot split and two-unit development.

Those paths do not create the same ownership, design, or permitting outcome. A duplex adds housing on one legal parcel. A lot split creates two legal parcels if the parcel map is approved and recorded. A combined strategy adds mapping and infrastructure questions to the housing design.

An ADU or a non-SB9 path may be more practical when the owner's main goal is housing or rental income rather than a separate parcel. Compare SB9 versus an ADU before choosing the most complicated route.

Planning And Public Works Have Different Roles

San Francisco's process involves more than one department. SF Planning reviews SB9 eligibility and compliance with applicable objective planning and design standards. An urban lot split also requires subdivision and mapping work through the San Francisco Public Works Office of the City and County Surveyor.

The City's SB9 page gives different filing directions based on project scope. A lot-split-only project starts with a Parcel Map application through Public Works and also requires the Planning supplemental materials. A duplex or combined project requires the Planning application and plans; a combined project also includes the Public Works subdivision process.

Public Works explains that parcel maps are governed by the California Subdivision Map Act, the San Francisco Subdivision Code, and local subdivision regulations. Mapping submittals, review comments, technical corrections, signatures, conditions, and recordation are separate from simply confirming that state SB9 criteria appear to be met.

Objective Standards And The 800-Square-Foot Protection

SB9 projects must comply with objective zoning, subdivision, building, and design standards that do not conflict with state law. San Francisco adopted SB9 Objective Design Standards, and the current application asks applicants to identify any objective standard for which relief is requested.

State law limits standards that would physically preclude two units on a parcel or prevent an allowed unit from reaching at least 800 square feet. That protection does not erase every local rule. The design still has to address the applicable building envelope, setbacks, exposure, open space, fire and life safety, and other objective requirements.

SF Planning's current guidance notes that side and rear setbacks of up to four feet may apply outside an existing structure or a replacement in the same location and dimensions. The actual buildable area should be tested on a site plan rather than assumed from the minimum state numbers.

Access, Utilities, And Easements Can Decide The Layout

SF Planning warns that lot splits and duplex projects often need new electrical or water service and meters. Depending on the configuration, utility and physical-access easements may be required. The City recommends contacting PG&E and the San Francisco Public Utilities Commission early.

An early feasibility layout should test:

• How each parcel reaches the public right-of-way.
• Whether access and emergency circulation can meet current fire and building requirements.
• Where water, sewer, power, and other services can be extended.
• Whether cross-parcel utility or access easements are needed.
• Whether existing foundations, retaining walls, garages, stairs, or light wells block a practical split line.
• Whether utility work or site access makes the intended project disproportionately expensive.

The legal ability to record two parcels does not guarantee that both parcels can be developed economically.

Existing Buildings And San Francisco Parcel Geometry

San Francisco lots often contain improvements that were designed for one parcel. The existing building may sit close to a side property line, occupy much of the lot depth, or rely on rear-yard access and utilities that become complicated after a split.

Before choosing a parcel line, check:

• The surveyed lot dimensions and block-and-lot records.
• The footprint and location of every existing structure.
• Legal and practical access to the proposed rear or interior parcel.
• Setbacks from the new property line.
• Windows, exposure, open space, and separation between buildings.
• Slopes, retaining walls, drainage, and construction access.
• Historic-resource information and recorded Notices of Special Restrictions.

The strongest concept is usually the one that preserves a useful existing asset while creating a second parcel with a credible access, utility, and development strategy.

Tenant, Rent-Control, And Historic Review Comes Early

San Francisco's housing protections are a major part of the SB9 screen. The City's current guidance says a project is ineligible when it would demolish or alter qualifying tenant-occupied housing, and it identifies restrictions involving rent-controlled units and protected historic resources.

Do not treat occupancy as a simple owner statement. The application calls for evidence covering the relevant period, and the property's permit, tenancy, rent-control, Ellis Act, and historic records may affect the answer. When those issues are present, involve the appropriate planning, legal, and housing professionals before relying on SB9.

The Family Zoning Plan May Create Other Options

The 2026 Family Zoning Plan expanded housing capacity across substantial parts of San Francisco and introduced the Housing Choice-San Francisco Program. That means SB9 may not be the only path worth comparing, even when a parcel remains eligible.

For each property, compare the current base zoning and available programs against the owner's actual goal:

• Create a separate legal parcel.
• Add rental housing on one parcel.
• Build for family or multigenerational use.
• Preserve and improve the existing home.
• Sell or finance a separate asset.
• Avoid a mapping process when added housing is the only objective.

The best option is not automatically the one with the largest theoretical unit count. Timing, construction cost, site access, title, financing, and marketability can change the practical result.

Step-By-Step San Francisco SB9 Review

1. Confirm the address, block and lot, and current jurisdiction.
2. Review current zoning, height and bulk, special districts, historic information, environmental information, and permit history in PIM.
3. Confirm whether the current zoning is one identified by SF Planning for SB9 review.
4. Check tenant, rent-control, affordable-housing, Ellis Act, historic, hazard, and prior-split restrictions.
5. Verify the original lot area and test the 40/60 split with both parcels at or above 1,200 square feet.
6. Map existing structures, setbacks, exposure, open space, access, utilities, easements, slopes, and retaining walls.
7. Compare a lot split, duplex, combined SB9 project, ADU, Family Zoning Plan option, or no project.
8. Confirm the current Planning and Public Works submittal sequence for the chosen scope.
9. Prepare the survey, parcel map, plans, and technical documents only after the property appears workable.
10. Address agency comments, conditions, mapping corrections, signatures, and recordation before relying on separate-parcel rights.

Review the step-by-step SB9 lot split process, SB9 lot split costs, and mortgage considerations for an SB9 lot split before committing to a strategy.

Start With A San Francisco Property Review

Riechers can screen the current zoning, lot geometry, existing improvements, access, utilities, easements, planning constraints, and likely mapping path before an owner spends heavily on a complete application.

Homeowners comparing Bay Area jurisdictions can also review the Alameda SB9 guide or browse the California SB9 city guide hub. For the statewide framework, start with What is SB9?.

Start with the SB9 eligibility checker and include the San Francisco address, block and lot if available, existing use, occupancy history, and the owner's intended outcome.

No approval, schedule, unit count, value, financing, tax, sale, rental, or development outcome is guaranteed. Requirements can change, and final determinations belong to the applicable agencies and qualified professionals.

Frequently Asked Questions

Does San Francisco still allow SB9 lot splits after the 2026 rezoning?

SF Planning's Bulletin No. 8, updated June 24, 2026 after the Family Zoning Plan took effect, still describes SB9 review for current RH-1, RH-1(D), and RH-1(S) parcels. Because the 2026 plan changed zoning across substantial parts of the City, check the parcel's current PIM report rather than relying on its former zoning or a blanket citywide statement.

What is the minimum lot size for a San Francisco SB9 lot split?

The City's current guidance says the original parcel must be at least 2,400 square feet, each resulting parcel must be at least 1,200 square feet, and the split must remain within the 40/60 area rule.

Which San Francisco zones may qualify for SB9?

Current SF Planning materials identify RH-1, RH-1(D), and RH-1(S). Zoning alone is not enough; occupancy, rent-control, historic, hazard, prior-split, and parcel-feasibility rules still apply.

Do I apply through SF Planning or Public Works?

Both may be involved. SF Planning reviews SB9 eligibility and planning standards. An urban lot split also requires the subdivision and parcel-map process through San Francisco Public Works. The filing sequence depends on whether the project is a lot split only, duplex only, or a combined project.

Can San Francisco require setbacks and design standards?

The City may apply objective standards that do not conflict with state SB9 protections. The current guidance discusses objective Planning Code and design standards, with state limits on rules that would physically preclude two allowed units or an 800-square-foot unit.

What should I check before paying for a survey or plans?

Confirm current zoning, lot area, occupancy and rent-control history, historic status, existing buildings, a practical split line, legal access, utilities, easements, slopes, retaining walls, and the current Planning and Public Works process. A concept-level engineering review can expose major conflicts before full design begins.

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

San Francisco:

• SF Planning Director Bulletin No. 8: Streamlined Housing Development
• SF Planning SB9 Streamlined Housing Development
• SF Planning SB9 Supplemental Application
• SF Planning Property Information Map
• SF Planning Zoning Resources
• San Francisco Family Zoning Plan
• SF Public Works Subdivisions and Mapping

Sources last reviewed: July 11, 2026.