You may have heard that AB 1033 lets California homeowners sell accessory dwelling units (ADUs), but figuring out what that actually means in practice can feel confusing.
If you’re considering adding a detached residential dwelling unit, an attached or junior ADU, or converting an existing accessory structure, understanding AB 1033 is essential.
Below is a breakdown of what AB 1033 ADU rules allow, how the process works, which cities have opted in or are currently reviewing it, and tips for designing an ADU to maximize future flexibility.
What is AB 1033? Understanding California’s ADU Law
Under existing law, homeowners could build:
- Attached accessory dwelling units
- Detached residential dwelling units
- Junior accessory dwelling units
- Accessory dwelling units connected to the main house; and
- Conversions of existing accessory structures
However, none of these could be legally conveyed separately from the existing primary residence.
Assembly Bill 1033 (AB 1033), a law that took effect in January 2024, changes this.
Homeowners with a proposed or existing dwelling or existing multifamily dwelling units can now create a condominium plan that allows a separate sale of the ADU while retaining ownership of the primary dwelling unit.
Some projects may also involve a qualified nonprofit corporation, which can expand affordability opportunities and help meet local housing goals.
How AB 1033 Works: The Basics Every Homeowner Should Know
Local Opt-In Requirement
AB 1033 is a state-mandated local program, meaning it’s optional for local governments. Homeowners can only sell an ADU separate from the primary dwelling if the local agency has adopted an accessory dwelling ordinance that allows it.
This applies to any ADU — whether detached, attached, or part of an existing multifamily dwelling — and ensures it meets subdivision, utility, building code, and zoning requirements before it can be conveyed separately.
For a separate ADU sale to be possible, the adopted accessory dwelling ordinance must meet the following:
- Permits accessory dwelling units to be conveyed separate from the existing primary residence
- Complies with the Subdivision Map Act and local subdivision ordinance
- Requires separate utility connections; and
- Aligns with local zoning ordinance, planning and zoning law, and the existing ordinance governing accessory dwelling units
Without a qualifying ordinance, an ADU cannot be sold independently.
Condominium Conversion Process
A proposed or existing dwelling can be converted into a condominium plan for separate ownership. The process includes:
- Preparing a condominium plan for the existing single-family dwelling and ADU
- Submitting the condominium plan to the local agency for review, following the procedures established by statutory provisions for subdivision and separate conveyance
- Ensuring compliance with local ordinances, zoning codes, the California Building Code, the local building code, the health and safety code, and the ordinance on accessory dwelling units
- Establishing separate utility connections directly for water, sewer, electricity, and gas; and
- Confirming compliance through a housing quality standards report and inspections by plumbing and mechanical officials
Once approved, the ADU becomes a complete independent living facility, eligible for sale to a qualified buyer, separate from the primary dwelling unit.
Key Requirements for AB 1033 Compliance
To sell an ADU separate from the primary dwelling, homeowners must:
- Form a Homeowners Association (HOA) under the Davis-Stirling Act, if needed for shared areas
- Install separate utilities or meet alternative rules set by the water or sewer system service provider
- Obtain lender approval for either the primary dwelling or ADU
- Meet all planning and zoning law, local building code, and health and safety code requirements; and
- Create separate property tax assessments and Assessor Parcel Numbers (APNs) for the ADU and the existing primary dwelling to ensure each unit is recognized as an independent property for tax purposes
Special situations may include an ADU located in a historically significant historic district or using a private sewage disposal system; in these cases, additional review and approvals from local agencies and plumbing and mechanical officials are required.
Note that Apex Homes does not provide legal advice. Homeowners should consult the official AB 1033 legislation and qualified professionals.
AB 1033 Participating Cities: Where Can You Sell Your ADU?
Because AB 1033 is a state-mandated local program, participation varies. As of late 2025:
Cities that Have Adopted AB 1033:
- San Francisco – as of July 2025
- City of Santa Cruz – as of February 2025
- Santa Monica – adopted on October 2024
- San Jose: as of July 2024
Cities Currently Reviewing AB 1033:
- Santa Clara
- Cupertino
Each jurisdiction establishes how to govern separate interests, manage multifamily dwelling residential conversions, and apply rules objectively to ensure no personal or subjective judgment affects approvals.
Homeowners and buyers can check the official websites of their local agencies to view the current status of AB 1033 adoption and implementation.
Who Benefits from AB 1033?
AB 1033 creates opportunities for both homeowners and buyers, transforming how accessory dwelling units are developed, sold, and owned in California.
Benefits for Homeowners
With a qualifying accessory dwelling ordinance, homeowners can:
- Unlock home equity without selling the primary residence
- Finance new construction through proceeds from a separate conveyance
- Monetize land without taking on landlord responsibilities
- Sell ADUs later while retaining the primary dwelling
- Increase property value by adding said accessory dwelling units
Whether adding a detached accessory dwelling unit, converting an existing accessory structure, or designing a proposed multifamily dwelling, homeowners gain long-term flexibility under AB 1033.
Benefits for Buyers
Buyers — especially first-time homeowners — benefit by:
- Accessing smaller, more affordable, and complete independent living facilities
- Entering competitive neighborhoods
- Purchasing existing multifamily dwelling units or detached accessory dwelling units; and
- Building equity instead of paying rent
The ability to create a separate condominium interest comes from state legislation, not the local agency, although each jurisdiction must adopt an ordinance to implement it.
AB 1033 vs. SB 9: What’s the Difference?
Although often compared, AB 1033 and Senate Bill 9 (SB 9) serve different purposes.
Key Distinctions
| FEATURE | AB 1033 | SB 9 |
| Type | Separate sale of ADUs | Lot split + duplex construction |
| Land Division | No physical split | Physical lot split |
| Applicability | Local opt-in | Statewide |
| Regulatory Complexity | High (example: HOA, subdivision map) | Moderate |
| Ideal for | Selling ADUs as condos | Creating two separate parcels |
AB 1033 focuses on ownership division, creating a legally conveyed separate unit while retaining the land. Meanwhile, SB 9 focuses on lot division, creating distinct parcels. Together, they complement California’s long-term housing strategy.
Building an ADU with AB 1033 in Mind: Strategic Planning Tips
Even if your city hasn’t adopted AB 1033 yet, designing a proposed accessory dwelling unit for future separate conveyance ensures flexibility.
Design Considerations for Maximum Resale Value
When planning a proposed accessory dwelling unit, identifying adequate sites and considering features that can enhance resale value are crucial. Review how each element — from layout to utilities — can make the ADU more desirable and ready for separate conveyance under AB 1033.
Here are a few things to consider:
- Detached layouts for marketability
- Private entrances separate from the primary residence
- Modern finishes appealing to small-home buyers
- Energy-efficient systems
- Separate utility connection directly from day one
- Compliance with local zoning ordinance and existing ordinance governing accessory dwelling units
- Outdoor space and parking; and
- Clear pathways for condominium plan conversion
For example, private entrances, independent HVAC systems, and flexible floor plans make the unit appealing to buyers; and future-proofing with energy-efficient appliances and durable finishes reduces maintenance costs and enhances long-term value.
Using a layout with the same physical dimensions as common small-home plans can also streamline construction and support future resale value.
Ensuring AB 1033 Compliance From the Start
Partnering with an experienced ADU builder like Apex Homes ensures your project is future-ready and aligns with existing laws and government code proposed standards. A builder can help with:
- Understanding accessory dwelling ordinance rules
- Converting a multifamily dwelling unit into separate interests
- Navigating statutory provisions establishing procedures
- Forming and managing HOAs
- Coordinating with plumbing and mechanical officials; and
- Addressing private sewage disposal systems, onsite water treatment systems, or historic district considerations
Book a free consultation with Apex Homes today to explore planning and building an ADU under AB 1033!
Looking Ahead: Opportunities with AB 1033
AB 1033 ADU rules mark a new chapter for California homeowners. The ability to sell an ADU separately — without splitting the lot — creates opportunities for financial strategy, family planning, and expanding homeownership.
While navigating planning and zoning law, local agency rules, utilities, and subdivision mapping can be complex, the long-term benefits of multiple accessory dwelling units are substantial.
FAQs
What is AB 1033?
AB 1033 is a California law that allows cities and counties to adopt ordinances that allow homeowners to sell accessory dwelling units separately from the primary home through a condominium plan, provided local agencies establish objective rules and that all subdivision and utility requirements are met.
Can I sell my ADU in California?
Yes, but only if your local government has adopted an AB 1033 accessory dwelling ordinance. You must complete a condo map, create separate utility connections, receive lender approval, and meet all planning, zoning, and building code standards before selling the ADU independently.
Can I buy an ADU in California?
Yes, buyers can purchase an ADU converted under AB 1033 as an independent home. This creates more affordable homeownership opportunities, especially in high-cost areas, by allowing smaller code-compliant units to be conveyed separately from the main residence.
What is the difference between AB 1033 and SB 9?
AB 1033 allows the separate sale of an ADU as a condominium interest without splitting the lot. SB 9 mandates statewide approval for lot splits and duplex construction. AB 1033 divides ownership, while SB 9 divides land, offering different pathways for expanding housing supply.