California is facing a housing shortage. Many cities are limited by single-family zoning. Senate Bill 9 (SB 9) was introduced to help address this problem. It allows property owners to develop two units on a single lot or split a lot into two parcels.
This law creates new opportunities for homeowners, developers, and investors. Understanding SB 9 can help you make informed decisions. In this guide, we explain the basics, how it works, and what you need to know to start a two-unit development project.
SB 9 Overview: Two-Unit Development & Lot Splits
Vacant Lot
Add up to 2 units without a lot split. With a lot split, up to 4 units possible.
Single-Family Home
Can add 1 or 2 new units + ADUs/JADUs. With lot split, total up to 4 units.
Nonconforming Duplex
SB 9 allows adding 2 units + ADUs. With lot split, total units may reach 4.
Single-Family Home + ADU
Can add 1 more unit + ADU/JADU. With lot split, total units can reach 4.
*Illustrations based on preliminary analysis of SB 9. Actual approvals depend on local regulations. ADU = Accessory Dwelling Unit, JADU = Junior Accessory Dwelling Unit.
Why SB 9 Matters for Two Unit Development
SB 9 is more than just a law. It changes how single-family properties can be developed.
Before SB 9, most cities restricted development to one house per lot. This limited housing options and made it difficult to increase density in neighborhoods. SB 9 allows more units without lengthy approval processes.
For homeowners, it can mean extra rental income or the ability to sell additional units. For developers, it opens new possibilities for building duplexes or splitting lots.
Here is a quick summary of why SB 9 matters:
Allows two units on a single lot.
Permits lot splitting in qualifying areas.
Reduces lengthy city approvals.
Helps address housing shortages in California.
SB 9 is not for every property. Certain areas, like historic districts or high fire risk zones, are excluded. Later sections will explain eligibility and requirements in detail.
What Is SB 9? A Simple Explanation
SB 9, also known as Senate Bill 9, is a California law passed in 2021. It allows homeowners and developers to build duplexes or split lots in areas previously limited to single-family homes.
The Basics of Senate Bill 9
Build two units on a single lot.
Split one lot into two separate parcels and build units on each.
Cities must approve qualifying projects under objective standards without discretionary hearings.
SB 9 makes it easier to add housing while following clear rules. This reduces delays caused by traditional zoning restrictions.
How SB 9 Changes Zoning Rules
Under SB 9:
Traditional single-family zoning limits are relaxed.
Local governments must approve qualifying projects based on objective standards.
Developers and homeowners can build more units without complex hearings.
| Feature | Before SB 9 | After SB 9 |
|---|---|---|
| Units per lot | 1 | 2 (plus potential lot split) |
| Approval process | Subjective, lengthy | Objective, ministerial |
| Owner occupancy | Usually required for new builds | Required only for lot splits in some cases |
SB 9 encourages small-scale density while maintaining neighborhood character. It also provides more housing options for buyers and renters.
Understanding Two Unit Development Under SB 9
Two-unit development is the core of SB 9. It allows more housing on a single property. There are two main approaches:
Duplex on a single lot
Lot split with units on each parcel
What Counts as a Two Unit Development?
Two primary units on the same lot.
One new unit added to an existing property.
Duplexes or separate buildings that meet city standards.
Difference Between Duplex vs. Lot Split + Units
| Feature | Duplex Only | Lot Split + Units |
|---|---|---|
| Number of Parcels | 1 | 2 |
| Max Units | 2 | 4 (2 on each lot) |
| Can Sell Parcels Separately | No | Yes |
| Owner Occupancy | Sometimes | Typically yes |
Choosing the right option depends on your goals. A duplex may be simpler to build. A lot split can provide more long-term flexibility.
Two-unit development can increase property value and generate rental income. It also allows homeowners to make better use of underutilized land.
Eligibility — Can Your Property Use SB 9?
Not every property qualifies for SB 9. There are specific rules you must meet before starting a two-unit development. Checking eligibility early can save time and money.
Property Requirements
To use SB 9, your property must meet certain criteria:
Zoned single-family residential (like R-1).
Not located in flood zones, wetlands, or high fire-risk areas.
Not part of historic districts or protected farmland.
Must have access to utilities and roadways.
Here’s a quick checklist to see if your property is eligible:
| Requirement | Yes | No |
|---|---|---|
| Single-family zoning | ☐ | ☐ |
| Not in protected area | ☐ | ☐ |
| Utilities available | ☐ | ☐ |
| Meets minimum lot size | ☐ | ☐ |
If your property meets most of these conditions, you may be able to proceed with a two-unit development.
Owner Occupancy & Other Rules
SB 9 also includes some owner requirements:
If you split a lot, the owner must live on one of the parcels for at least 3 years.
Properties with long-term tenants may have restrictions.
Rental income does not disqualify the project, but local rules may apply.
This ensures that the law encourages homeowners rather than outside developers in some cases.
SB 9 Development Standards You Must Know
Even if your property is eligible, you must follow development standards. Cities can enforce objective rules for height, setbacks, and design.
SB 9 Return Potential 📈
Talk to JDJ Consulting about SB 9 feasibility, permits, and planning.
Size, Setbacks & Design Rules
Each new unit must be at least 800 sq ft.
Typical side and rear setbacks are 4 feet.
Local governments can add additional objective design standards, such as roof pitch, window placement, or facade treatment.
Following these standards ensures your project passes the ministerial review without delays.
Lot Split Rules
If you want to split your lot:
Lots should generally follow a 60/40 ratio.
Each lot must meet minimum size requirements (usually 1,200 sq ft).
Only one SB 9 lot split is allowed per original lot.
Parking, Access, and Utilities
Usually one parking space per unit is required, but some cities waive this near transit.
Units must connect to water, sewer, and electricity.
Driveways and walkways should meet local safety standards.
By following these rules, your two-unit development will be approved more quickly and avoid unexpected costs.
Step-by-Step SB 9 Two Unit Development Workflow
Developing two units under SB 9 can feel complicated. Breaking the process into clear steps makes it easier. Here’s a roadmap to help you plan your project.
1. Pre-Feasibility & Eligibility Check
Before you start designing or applying for permits, check:
Zoning — Is your property R-1 or single-family?
Lot size — Does your property meet minimum size requirements?
Environmental exclusions — Is it in a flood zone, wetland, or fire-risk area?
This early assessment helps avoid wasted time or investment.
2. Design & Planning
Once your property is eligible, you can plan your development:
Preliminary site plan — Decide where units and driveways will go.
Unit design — Consider size, layout, and style.
Compliance check — Make sure designs meet setbacks, height limits, and other local standards.
3. Application Submission
Submit your applications to the city:
Lot split application (if applicable)
Building permits for new units
Owner occupancy affidavit, if required
4. Ministerial Review
City officials check your application against objective standards.
No public hearings are required for qualifying SB 9 projects.
Approval is typically faster than traditional discretionary permits.
5. Construction & Compliance
Start construction once permits are approved.
Ensure inspections are scheduled at required stages.
Receive final certificate of occupancy after passing all inspections.
Here’s a quick overview table of the workflow:
| Step | Key Actions | Outcome |
|---|---|---|
| Pre-Feasibility | Check zoning, lot size, exclusions | Confirm eligibility |
| Design & Planning | Site plan, unit design, compliance check | Ready for submission |
| Application Submission | Submit permits and forms | Await ministerial approval |
| Ministerial Review | City reviews objective standards | Approval or minor revisions |
| Construction & Compliance | Build units, inspections | Units ready for occupancy |
Financing an SB 9 Project
Financing is an important part of any development. Planning your budget early ensures your project stays on track.
SB 9 Two-Unit Development at a Glance 🏗️
Single-family zoned lots that meet state criteria.
Two units or lot split with units on each parcel.
Ministerial review with no public hearings.
Typically faster than traditional entitlements.
Funding Options
You can use several funding sources for SB 9 projects:
Construction loans — Short-term loans to fund building.
Home equity lines of credit (HELOCs) — Use your property’s equity.
Joint ventures — Partner with investors to share costs and profits.
What Lenders Look For
Lenders want to see:
Feasibility studies and accurate cost estimates
Property value versus projected construction costs
Permits and approvals in place
A clear financial plan improves your chances of approval and reduces delays.
Example Budget Table
| Expense Category | Typical Cost Range | Notes |
|---|---|---|
| Land/Property Acquisition | $300,000 – $600,000 | Depends on location |
| Design & Permitting | $20,000 – $50,000 | Architectural, engineering, and fees |
| Construction | $150,000 – $400,000 | Per unit, varies by size and materials |
| Utilities & Infrastructure | $10,000 – $30,000 | Connect water, sewer, electricity |
| Contingency | 10% of total | Covers unexpected costs |
Proper planning and budgeting reduce risk and help you complete the project successfully.
Expected Costs & ROI for Two Unit SB 9 Projects
Understanding costs and potential returns is essential before starting a two-unit development project. Proper planning helps you decide whether a project is worth the investment.
Typical Costs Breakdown
Costs vary depending on location, lot size, and construction type. Here is a general estimate:
Land costs — Price of acquiring the lot if you don’t already own it.
Design & permitting fees — Architects, engineers, and city fees.
Construction budgets — Building materials, labor, and contractor costs.
Utilities & infrastructure — Water, sewer, electricity, and driveway installation.
Potential Returns
SB 9 projects can generate income in different ways:
Rental income — Renting one or both units can cover mortgages and expenses.
Selling units — You can sell one unit while keeping another.
Property value appreciation — Additional units often increase overall property value.
Typical SB 9 Cost Breakdown 💰
Data source: California SB 9 guidelines & regional development averages
With careful planning, SB 9 projects can offer strong long-term returns.
Common Challenges and How to Overcome Them
Even though SB 9 simplifies development, challenges can arise. Knowing these early helps you plan better.
Local Jurisdiction Nuances
Cities can have additional rules even under SB 9. Some may:
Require objective design standards.
Limit certain building types.
Add specific parking or landscaping rules.
Tip: Check your city’s planning department before designing your project.
Neighborhood Concerns
Neighbors may worry about:
Increased density
Parking shortages
Changes in neighborhood character
Solution: Communicate early, show how your project complies with all standards, and explain benefits like improved property upkeep.
Infrastructure & Hidden Costs
Unexpected costs can include:
Upgrading water, sewer, or electricity
Site grading or soil stabilization
Unforeseen construction issues
Tip: Include at least 10% contingency in your budget.
Case Studies & Real-World Examples
Seeing SB 9 in action helps you understand possibilities and outcomes. Here are a few examples:
| City | Project Type | Outcome | Key Lesson |
|---|---|---|---|
| Los Angeles | Duplex on existing lot | Built 2 units with minimal delays | Close to transit, approvals faster |
| San Diego | Lot split + 2 units | Added 4 units total | Combining SB 9 with ADUs maximized space |
| San Jose | Duplex | Minor design revisions required | Local standards can require adjustments |
| Oakland | Lot split + duplex | Sale of one unit funded construction of second | Strategic financing improves ROI |
These examples show how planning, compliance, and location influence success. Each project is unique, but the principles remain the same.
SB 9 and Accessory Dwelling Units (ADUs)
SB 9 and ADUs can work together to maximize property potential. Understanding how they interact helps you plan efficiently.
How SB 9 and ADUs Interact
SB 9 allows two main units or a lot split with units on each parcel.
ADUs are secondary units that can be added to a property in addition to SB 9 units.
Combining both can increase rental income or property value.
When ADUs Count Toward Unit Totals
Cities may have rules limiting the number of units on a property.
ADUs are usually counted separately from SB 9 units.
Careful planning ensures you stay compliant with local zoning laws.
Creative Combinations
Some strategies include:
Adding an ADU above a garage while building a duplex under SB 9.
Using ADUs on newly split lots to maximize rentable space.
Combining SB 9 and ADUs to create a small multi-unit investment property.
These approaches allow flexible design and financial options while following the law.
Future of SB 9 — Trends & Legislative Changes
SB 9 is still relatively new, and local implementation is evolving. Keeping an eye on trends helps you make smart decisions.
Legislative Updates
Cities continue to clarify objective standards.
Some updates address owner-occupancy rules, parking, or lot split limitations.
Developers must stay informed about new interpretations to avoid delays.
Market Adoption Patterns
Urban areas near transit are adopting SB 9 faster than suburban neighborhoods.
Homeowners are using SB 9 to add rental units or increase property value.
Investors are combining SB 9 with ADUs for small multi-unit projects.
Key Takeaways
SB 9 encourages small-scale density in single-family neighborhoods.
Local rules still matter — compliance is essential.
Proper planning, financing, and design can maximize returns.
Conclusion — Is SB 9 Right for You?
SB 9 provides opportunities to develop two units or split a lot in California. It can increase property value, generate rental income, and create more housing in single-family neighborhoods.
However, it’s not for every property. You need to:
Check zoning and environmental restrictions.
Follow development standards like setbacks, unit size, and parking.
Plan your budget and financing carefully.
When done right, SB 9 projects can be profitable and efficient. Careful planning, compliance with local rules, and smart design choices are key to success.
Take the Next Step with JDJ Consulting
If you’re considering a two-unit development under SB 9, JDJ Consulting can help. Our team guides you through:
Property eligibility assessment
SB 9 lot splits and two-unit planning
Permit applications and compliance
Cost planning and project financing
Contact us today to discuss your property and see how SB 9 can work for you.
- Call: (818) 793-5058
- Free consultation: JDJ Consulting Contact Page
Is Your Property SB 9 Ready? 🧠
- ✔️ Zoned single-family residential
- ✔️ Outside high fire or environmental hazard zones
- ✔️ Access to utilities and public street
- ✔️ No rent-controlled housing removed
If you answered “yes” to most, your property may qualify.
FAQs About Two Unit Development SB 9
What is SB 9 and how does it apply to two unit development?
SB 9 is a California law that lets homeowners build two housing units on a single‑family zoned lot or split that lot into two parcels to build units on each. It applies only in areas zoned for single‑family homes and streamlines approvals through objective ministerial review. This means cities must approve qualifying projects without discretionary hearings.
Who is eligible to use SB 9 for a two unit project?
To qualify, your property must be in a single‑family zone and not in restricted areas like flood plains, wetlands, historic districts, or high fire hazard zones. It must also have access to utilities and a public right‑of‑way. Projects demolishing affordable or rent‑controlled housing may be excluded. Always check with your local planning department.
Can I split my lot under SB 9 and build on each parcel?
Yes. SB 9 lets you perform an urban lot split to divide a single‑family lot into two separate parcels. Each new parcel must be roughly equal in size (at least 40 % of the original) and meet minimum area requirements (often 1,200 sq ft). Once split, each lot may have up to two units under SB 9 rules. Association of Bay Area Governments
Do I have to live on the property to use SB 9?
If you are proposing an SB 9 lot split, you must sign an affidavit stating you intend to live in one of the units for at least three years. This requirement does not always apply if you are only building an additional unit without splitting the lot. Always check local ordinances for specifics. Oceanside CA
Can I rent out the units created under SB 9?
Yes, you can rent SB 9 units. However:
Short‑term rentals (less than 30 days) are generally prohibited by state law.
Long‑term rentals (30 days or more) are allowed.
You must still follow local rental regulations and safety standards. Petaluma
How many units can be built under SB 9 on one lot?
SB 9 typically allows:
Two primary units on a single lot, or
After a lot split, two units per new parcel (up to four total).
Accessory dwelling units (ADUs) and junior ADUs may also be allowed depending on local rules. Westwood Homeowners Association
Do I need a public hearing for an SB 9 project?
No. SB 9 projects are reviewed ministerially, meaning:
No public hearings are required.
No subjective review by planning boards.
This helps speed up approvals as long as objective standards are met.
Can an HOA block my SB 9 project?
Homeowners associations (HOAs) may have covenants or restrictions that conflict with SB 9. Some local ordinances allow HOAs to enforce their rules, while others do not. You should review CC&Rs and consult with a planner or attorney before proceeding.
What standards must SB 9 units meet in terms of design?
SB 9 units must comply with objective standards such as:
Minimum unit size and height limits
Setbacks (often 4 ft from side/rear)
Local design standards that are objective
Cities can add objective rules but cannot impose subjective requirements.
How long does the SB 9 approval process take?
While times vary by city, many jurisdictions aim to complete ministerial review within 30–60 days of a complete application for completeness and eligibility. This is typically quicker than traditional discretionary reviews. Always check local timelines. Milpitas
Can I build an ADU with my SB 9 units?
Yes, in many cases you may add ADUs or junior ADUs (JADUs) in addition to SB 9 units, depending on local rules. Some cities restrict ADUs on split lots, while others allow them above duplexes or alongside primary units. Confirm with your planner.
What happens if my property is in a high fire zone?
Properties in Very High Fire Hazard Severity Zones or other restricted areas may be excluded from SB 9 or require additional safety conditions. Local fire safety measures may apply before approval. Moraga
Can I combine SB 9 and traditional subdivision laws?
No. SB 9 urban lot splits are a one‑time subdivision method under state law. They don’t require full subdivision approvals, but must still comply with state and local standards like the Subdivision Map Act.
Does SB 9 override local zoning rules?
Not completely. SB 9 overrides certain zoning limits on unit count, but local objective standards for setbacks, parking, and design still apply. Local planning codes must allow SB 9 projects that meet objective criteria.
Can I demolish an existing home under SB 9?
You can demolish the existing home to build new units, but there are limits:
Demolition of housing with rent‑controlled tenants or affordable restrictions may disqualify ministerial approval.
Check with your planner before planning demolition. City of Gilroy
Is neighbor notification required for SB 9 projects?
No. Under SB 9, neighbor notification is generally not required for ministerial review. This helps reduce delays and controversy over new units. However, some cities may still enforce neighborhood notification for other reasons.
Can SB 9 projects be sold separately?
Yes, if you complete an urban lot split and create two parcels, each parcel can be sold independently. This can increase flexibility and investment opportunities.
Are there parking requirements for SB 9 units?
Many cities require one parking space per unit. However, if the property is within 1/2 mile of a transit corridor or major stop, parking requirements may be waived. Always confirm with local guidelines.
Can I do more than one SB 9 lot split on the same property?
No. SB 9 allows only a one‑time lot split for each original property. You cannot split again under SB 9 after the initial division. Oceanside CA
What zoning types do SB 9 rules apply to?
SB 9 applies only to single‑family residential zones (R‑1) or equivalent. It generally does not apply to multifamily zones like R‑2, R‑3, or commercial zoning.
