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How Californians Can Build 2 Duplexes on One Lot in 2022

Updated: May 4, 2022

2022 begins with a bang throughout California. Learn how Californians can build 2 duplexes on one lot in 2022.

Known as the SB 9 law (Senate Bill 9), starting January 1, 2022, every homeowner with a residential lot of at least 2,400 square feet can qualify to add three housing units for extra income.

According to Fox KTVU News: “This is a Free for All”. The new law allows single-family homeowners to turn their lot “into two or even four units”.

Save Money: If you want to Do It Yourself (DIY) by building one or three more housing units on your property, we’ll give you some money-saving tips.

Example of a duplex


2022 begins with a new California law allowing thousands of single-family homeowners to split their lot into two and develop up to three more housing units for four.

Several options exist for qualifying lots to split and add more housing units for a maximum of four. Like, building two duplexes after tearing down your residence.

• Tiny home kits bought online, delivered, and assembled as a duplex cost less than building one. Many tiny home kits sell for around $9,000 each. Just add electricity and plumbing connections.

• 40-foot shipping containers can convert into 2-bedroom homes or connect into duplexes for less than building one. One example is a 2-bedroom fully finished for $90,000. Just add electricity and plumbing connections.

• 410,000 California lots are “market feasible” for a split and development.

• 28,500 San Diego County lots are also “market feasible”.

• Split & Develop for Profits: Qualifying California homeowners can expect rental income, increased property value, and wealth-building with this new law.

• Possible Loophole: Currently, California law firms have not answered the question: Can a homeowner joint venture with a developer to split and develop?

Here’s How New California Law Lets Homeowners Build 2 Duplexes in 2022

California enacted SB 9 to increase housing and combat a statewide housing shortage. California homeowners can tear down their existing single-family homes, split their lot into two and develop two duplexes.

Other options exist like keeping the original house, splitting the lot into two, and building up to three more housing units.

But, before you start calling a developer or a general contractor you need to know the new law’s requirements.

How to Qualify for SB 9 Lot Splitting and Development of More Housing

SB 9 Limitations

Location – The new law limits single-family parcels (lots) from developing extra housing located in these three areas:

  • Fire hazard zones;

  • Historic districts; and

  • Rural areas.

Lot Size Minimum – Residential lots split into two must contain at least 1,200 square feet in each lot. Yet, a local agency can allow a lower minimum.

Residential Use – Only residential housing allowed with no commercial offices or spaces.

Short-Term Rentals – None of the housing units are short-term rentals. They must rent for longer than 30 days.

SB 9 Allows

Urban areas – and urban clusters (including suburbs) in residential zones (no commercial or industrial zoning) qualify.

Prohibits Local Interference – County, city, and local jurisdictions are prohibited from interfering with any proposed lot split and development when their local ordinances or rules prevent such developments. However, the homeowner must file an affidavit stating the intention to live in one of the units as the permanent residence at least 3 years from the date of lot split approval.

Faster Development Approval – County, city and local jurisdictions can’t require hearings or discretionary review before approving the development.

Only Exceptions – The only exceptions for the county, city and local jurisdictions disapproval are:

  • The project creates a specific adverse impact on;

  • Public health and safety;

  • The physical environment; and

  • No adequate mitigation options exist.

How SB 9 Affects Local Zoning

Besides, what we explained above, questions rose about specific local zoning requirements since SB 9 passed.

Parking – Many jurisdictions require a minimum number of off-street parking for housing developments to reduce street parking congestion. Thus, local agencies can require one off-street parking space per unit. Unless the units are close to public transit or a care-sharing vehicle location.

Setbacks – Most jurisdictions require homes to sit a minimum of four feet from the rear and side property boundaries known as a “setback”. Yet, new limits cannot be imposed on existing structures or new ones in the same location with similar dimensions as the original.

Non-Conforming – Existing structures built with a non-conforming zoning condition cannot be corrected by local agencies under SB 9.

No Right-of-Way – Local agencies are prohibited from asserting right-of-way usage or requiring offsite improvements to the new construction.

Only Objective Zoning Standards – SB 9 only allows local agencies to impose “objective” zoning standards on the subdivision and new housing construction of two units (duplex). These standards cannot preclude constructing two units of at least 800 square feet.

Environmental Quality Laws Limited – SB 9 does not allow the California Environmental Quality Act (CEQA) to apply. However, the California Coastal Act does apply for coastal area construction.

How to Split Your Lot to Develop Up to Four Housing Units

Split Your Lot to Develop Housing Units

California homeowners now have several options to split their lot to develop up to 4 housing units. The San Diego Union-Tribune published a chart showing all options:

Source: Licensed to use under the Fair Use Doctrine

As you see, the new law provides four options to split and develop more housing on your residential lot. These options let you create from two to four housing units on your two lots.

What is a Granny Flat?

The final option in the above San Diego Union-Tribune chart mentions a “granny flat” a self-contained living unit. The name “granny” refers to the manner a family accommodates aging parents on their land.

It’s also known as an Accessory Dwelling Unit (ADU) or a “mother-in-law” apartment.

Below, we explain how you can buy online and quickly assemble a tiny home kit that accommodates a single or couple.

How to Build Duplexes Yourself

Hiring builders and contractors to develop your two lots with new structures costs lots of money. Yet, you can Do It Yourself (DIY) and save money.

Several low-cost options exist for building housing structures on your property.

Tiny Wooden Homes Kits You Can Assemble

“10 tiny homes you can buy online” teaches you how to order online tiny cabins for under $9,000. Worth viewing to see the variety of tiny home styles you can order online.

The International Residential Code accepted by many U.S. communities building codes classifies a “tiny home” as a dwelling up to 400 square feet in floor space, not including lofts. Order kits online delivered to your door from U.S. manufacturers. These include the structures that you assemble requiring electrical and plumbing components.

Most kits only require two adults to assemble in three days. Kits include all these materials for the:

  • Floor;

  • Walls;

  • Roof; and

  • Pre-hung and glazed windows and double doors.

Here’s an image of the Allwood Summerlight Cabin Kit for $8,920 with 150 square foot space:

Source: Licensed for Use under the Fair Use Doctrine.

Here’s an image of the Cedarshed FarmHouse is 20 x 14 feet for $14,911:

Source: Licensed for Use under the Fair Use Doctrine.

View this image of the EZ Supply Modern 1 Bedroom Tiny House a converted 20-foot container for $28,000: It doesn’t require construction sold as a pre-built tiny house:

Source: Licensed for Use under the Fair Use Doctrine.

Check out the image of the Camp Reynolds Building, a two-story 448 square-foot tiny home 28 x 16-foot wood building for $24,123. The kit includes:

  • Four insulated windows with shudders;

  • A door;

  • Walls and trusses;

  • Required hardware, nails, and glue; and

  • Primed siding requiring paint.

Note: You will need to build a foundation and the floor along with adding electricity, plumbing, and sewer.

Source: Licensed for Use under the Fair Use Doctrine.

How to Maximize Space in Tiny Homes

Here are sites giving tips on how to maximize space in a tiny home:

Attach Two Tiny Homes to Create a Duplex

Why settle for a tiny single-family home when you can attach two tiny homes to make a duplex?

It’s economically feasible to spend a little more money and time to double your rent for greater cash flow and profit.

As claimed by Fox News above, “This is a Free for All”.

Where to Buy Tiny Homes from Builders

This site lists tiny home builders in all 50 states: The Best Tiny Home Builders in the US

Here is another site listing tiny house builders across America called Tiny Living.

Here’s one tiny home builder based in San Diego County called Zen Tiny Homes.

Convert 40 Foot Steel Shipping Containers into Homes

Shipping Container Homes Are Legal in California

How much does it cost to build a home from shipping containers?

According to Upnest, in October 2021 building an average home from shipping containers costs “around $10,000 to $35,000”. The price rises depending on how many amenities you intend to add.

Sizes: explains the two standard sizes:

  • 20 x 8 x 8 feet giving you a surface of 160 square feet; and

  • 40 x 8 x 8 providing a surface of 320 sq. ft.

Costs: Used containers cost between $1,500 to $2,800. While a 40-foot costs from $3,500 to $4.500.

Labor costs: Expect at least $10,000 for labor plus planning, permits, architect design, and structural engineering fees.

Longevity: Since steel containers are built to last 25 years in all weather conditions they last longer with the right care. If you buy used containers make sure they come with no rust.

Construction and Installation: You will need to lay a concrete foundation, install insulation, and add from these features:

  • Electricity;

  • HVAC system;

  • Flooring;

  • Interior doors and walls;

  • Plumbing (bathtubs, shower, sinks);

  • Shelving and closets; and

  • Windows.

Example of shipping containers converted into a home

Pre-Made Container Homes

If you don’t want to deal with all the above time and expenses, you can buy pre-made container homes.

Pre-made container homes start at $30,000 and include amenities like:

  • Bedroom space;

  • Kitchen;

  • Bathroom; and

  • Rooftop patio.

Note: You will still need to paint the interiors and buy furniture.

Where to Buy Pre-Made Container Homes

Here’s a site that lists “5 of Our Favorite Shipping Container Companies in North America” along with great photos of what their prefab container homes look like.

This is the site for a pre-made container home factory based in Missouri called Custom Container Living.

Similarly, here is another pre-made container homes manufacturer’s site based in Pennsylvania called CW Dwellings.

Take Advantage of Container Home Floor Plans Maximizing Space

Buying 40-foot shipping containers converted into a home requires maximizing space. Here’s a solution offered by the dwell website showing “9 Shipping Container Floor Plans that Maximize Space”.

Their 19 photos show different styles available to you from different manufacturers.

Here’s a 40 Foot Container Floor Plan for 2 Bedrooms:

Source: Licensed for Use under the Fair Use Doctrine.

Here’s an image of a High-End 40 Foot Container 2 Bedroom Home that sells for $90,000:

Source: Licensed for Use under the Fair Use Doctrine.

As you see, you can buy beautiful container homes as separate single-family homes or as a “granny flat” Accessory Dwelling Unit (ADU).

How Many Lots Qualify in California?

Last September, the UC Berkeley Terner Center published a report showing thousands of lots in the 10 most populous California counties. View the report to see how many lots are ‘market feasible” to split and develop. The report claims 410,000 lots in California are “market feasible”.

28,500 Lots are Market Feasible to Split and Develop in San Diego County

WeLease Property Management Company recently published a blog post titled: How to Develop 28,500 Lots in San Diego County in 2022”. It explains the new law and what lots qualify and the requirements in greater detail.

The Terner Center report identified 398.500 eligible lots in San Diego County with only 28,500 lots as market feasible for developing 54,500 new housing units. Check out the screenshots of the relevant Terner Center report about San Diego below.


San Diego County

This screenshot from the Terner Center report shows San Diego County.

Source: Licensed for Use under the Fair Use Doctrine.

City of San Diego

The City of San Diego has 133,000 eligible lots qualifying under SB 9. Yet, only 7,000 lots are considered market feasible for developing 13,000 new housing units.

This screenshot from the Terner Center report shows the City of San Diego.


Source: Licensed for Use under the Fair Use Doctrine.

If You Don’t Want to Develop Your Lot, Work with a Developer

Splitting your lot and developing extra housing takes time and money. The alternative is to contract with a developer to do all the work. Yet, you are still required to live in one of the units as your permanent residence for at least three years.

Loophole: One unanswered question that homeowners have about SB 9 is whether you can contract with a developer? Live in one unit, and joint venture with a developer to build the other units and share the profits from the rents and eventual sales. So far, no attorney has addressed this loophole. Contact an experienced California real estate lawyer to pursue this potential loophole.

Read how the Best, Best & Krieger law firm with “200 attorneys in 10 offices across California” explains the new SB 9 law.

Also, the Gibson & Dunn law firm with over 1,500 lawyers in 20 worldwide offices including 5 in California summarized the SB 9 law.

Plus, the law firm Holland & Knight with three offices in California summarized SB 9.

Yet, neither of these three law firms addressed whether California homeowners can joint venture with developers to split and develop.

Neither of these 3 California law firms answered the question: “Can I contract with a developer to split and develop my lot and share the rents and profits as a joint venture?”

How Californians Can Build 2 Duplexes on One Lot in 2022 – Conclusion

Once you learn how a new California law lets homeowners build 2 duplexes, you can become wealthier. Here's how:

The 2022 year starts with a new California law letting thousands of California homeowners split their lot in two to develop up to three more housing units;

• Options exist how to split qualifying lots to add another home, or a duplex, or tearing down the home to build two duplexes;

• Homeowners can buy tiny home kits online, delivered, and assembled or connected to create a duplex for much less than building a duplex;

• 40-foot shipping containers can be bought online, delivered, and converted into 2-bedroom homes or connected into duplexes for less than building a home or duplex;

• California has 410,000 lots considered “market feasible” to split and develop;

• San Diego County has 28,500 qualifying lots; and

• California homeowners using this new law can expect rental income, increased property value, and wealth building.

Work with a Developer

If homeowners do not want to spend the time and money converting tiny homes and 40-foot containers into duplexes, they might try to work with a developer. Currently, the new law remains unclear whether qualifying homeowners can contract with developers to develop and share the rents and sales profits as a joint venture.

Seek Legal Counsel

We advise viewers to consult with an experienced California real estate attorney to explore if this possible joint venture with a developer can bear fruit under the new law.

Need a San Diego County Realtor to Help You?

SoCal Lifestyle Realty offers experienced Realtors for selling. buying, or investing in homes throughout San Diego County.

Contact us to earn more about this exciting new law and how we can help you to use its benefits to prosper.

Need a Property Management Company in San Diego County?

WeLease Property Management Company can help you find qualified tenants for your new rentals in San Diego County. Let us take all the landlord stress off your hands. We handle everything from advertising and interviewing potential tenants, signing lease agreements, collecting rents, dealing with maintenance, tenant emergencies, and repairs.

Contact us to learn more about our professional services and how we can save you time, money, and stress.

Steven Rich, MBA – Guest Blogger

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If you're living around the Texas area, check out small house builders with various available home designs such as granny flats, lofts, adu, and more.

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