California ADU Law: The Ultimate Guide

What Qualifies as an Accessory Dwelling Unit (ADU)?

The state of California defines an ADU as a living space that shares a lot with a primary dwelling but functions independently. ADUs can either be attached (connected to the primary house) or they can be completely detached (standalone), but they need to contain a kitchen, a bathroom, and a separate entrance to be considered fully independent.

ADUs don’t have to be new construction. Many homeowners choose to convert other secondary structures like garages into a guest house, granny flat, or in-law suite. These garage conversions are considered ADUs.

Some homeowners also choose to convert an unfinished basement or guest bedroom into an independent living space. If an accessory dwelling is built within the footprint of the existing home, it is known as a JADU or Junior ADU.

The maximum unit size for ADUs in most municipalities is 1200 square feet, and JADUs can be no larger than 500 square feet.

You can read more about JADUs and ADUs here.

ADUs, whether detached or converted spaces like garages, must include a kitchen, bathroom, and private entrance to be considered fully independent living spaces.

Are There Any Restrictions on Renting Out an ADU in California?

Yes, rental restrictions exist, though they are less strict than in previous years, thanks to AB 976.

AB 976 – Owner-Occupancy Requirements

Until this year, homeowners looking to rent out their ADU or their single-family home still had to live on the property. This means that homeowners looking to rent out their ADU had to live in the main home and vice versa.

However, as of January 2024, the state passed AB 976, which removed that requirement. This means that cities and counties cannot force homeowners to live on the property in order to rent it out..

Key Provisions

By removing this provision, the state not only increased the rental income potential of any given property (as homeowners can now rent out their single-family house and their ADU), but also added more potential rental properties to the housing market.

When it comes to short-term rentals (STRs) under 30 days, cities and municipalities are allowed to place restrictions or even outright bans. This means that while you may be able to rent all the structures on a property out on a longer lease, renting any unit for under 30 days may be prohibited.

AB 976 eliminates owner-occupancy requirements, giving homeowners more freedom to rent out both their ADU and primary residence. However, short-term rentals may still be restricted by local laws.

What are the Rules for Building an ADU in California?

Many of the rules pertaining to ADU builds were put in place to make the construction process easier for homeowners to navigate. For example, cities now make pre-approved plans available to homeowners and must review permit applications within 60 days, both of which help expedite the building process. However, in order for a permit to be approved, certain codes must be followed pertaining to setbacks, fire safety, and zoning.

AB 434 – Pre-Approved ADU Plans

AB 434 helped expedite the development of ADUs by making pre-approved plans accessible to homeowners.

Pre-approved plans are those that have been accepted by the city and already comply with all necessary building and zoning codes. These plans come in a variety of sizes and layouts.

Homeowners can choose to submit these plans exactly as-is or customize them slightly to better suit their needs. If the customizations are minor, such as moving window locations, these can often be done online by the homeowners. If the customizations are more extensive, an architect may be necessary. Also, when submitting these pre-approved plans, homeowners still need to be mindful of following setback limits, which generally state an ADU must be at least 4 feet away from a property line.

Key Provisions

Along with allowing pre-approved plans, AB 434 sets other standards.

• Setback and height restrictions: For most ADUs, the setback requirement is 4 feet from the property line. When it comes to height, AB 434 states that cities must allow ADUs to be at least 16 feet high, though if the property is within half a mile of public transit or has an existing two-story structure, that height limit is increased to at least 18 feet. This is done to create more potential rentals in areas with reliable transit.
• Parking: AB 434 significantly reduces the previously stated parking requirements for ADUs. Previously, many cities stated that an off-street parking space must be made available for every bedroom. This is no longer the case. If your ADU is close to public transit, you may not need to provide any off-street or permit parking for your renters at all.
• Design and building code standards: Recent law streamlines both design and building codes to allow for more consistency statewide. This streamlining was done to make building approvals easier and quicker.
• Fire Safety: AB 434 clarifies that fire sprinklers are generally not required in ADUs if they are not required for the main home. It also states that secondary structures must be 5 feet from any existing building to prevent fire from spreading from one structure to the other.
• Compliance with Local Zoning: As with streamlining building codes, setting baseline zoning standards was done to make the permitting process easier for homeowners, giving them more certainty and reducing the impact of overly restrictive local rules. This ensures that ADUs can be easily built in nearly every city in California.

AB 1033

AB 1033 opens the possibility for homeowners to sell their ADU separately from their main home. This allows homeowners to get access to some of their home equity without moving or taking out a loan and creates more reasonably priced inventory for first-time homebuyers.

However, unlike many of the provisions in AB 434, AB 1033 does not mandate that cities allow this. It merely gives them the option. To see if your city allows for ADU sales, you can read our deep dive here.

Changes to the 60-Day Rule

California’s 60-Day Rule states that the city must review and either approve or deny an ADU permit application within 60 days. This was done in an effort to prevent bottle-necking early in the process and get ADU builds off the ground more quickly. In fact, thanks to the 60-Day Rule, most builds at Better Place Build & Design are completed within 8-12 months.

AB 2221– Streamlining ADU Approval Processes

Assembly Bill 2221 was passed in an effort to streamline the ADU building and permit approval process across the state. Before the passing of this bill, certain municipalities passed overly restrictive ordinances that would prevent the building of ADUs on many residential properties. For example, some city councils required setbacks greater than 4 feet from the property line. These extreme setback requirements could limit the size of ADU a homeowner could build or, in some cases, could prevent them from building an ADU entirely. AB 2221 stepped in and said that no city in California can require setback requirements greater than 4 feet.

Key Provisions

AB 2221 also set certain standards for converting detached garages, basements, and other livable structures into ADUs. Converting existing spaces is generally more cost-effective for homeowners and more environmentally friendly.

AB 2221 also promotes the building of JADUs by stating that attached garages can be converted into junior accessory units, and (unlike ADUs) these units do not have to have an independent bathroom. JADUs can share a bathroom with the main house so long as the bathroom has interior access to the main living area of the home.

California’s ADU rules simplify construction. AB 434 introduces pre-approved plans, reduces parking requirements, and clarifies height and setback standards for faster permitting.

Upcoming Changes to Accessory Dwelling Unit (ADU) Laws in California

ADU legislation is far from over. Here are some of the upcoming changes homeowners can expect when it comes to ADU laws.

SB 1211 – Enhancements for Multi-Family Properties

Much of the conversation surrounding ADUs thus far has revolved around single-family homeowners, but SB 1211 allows for owners of multi-family lots, like apartment buildings or condo complexes, to build ADUs, too.

Increased Detached ADUs

While most single-family homeowners can only build 1 ADU and 1 JADU on their property, owners of existing multi-family lots can build up to 8 detached ADUs on their lot, provided the number does not exceed existing units. This means that an apartment building with 8 or more apartments can build up to 8 detached ADUs.

Parking Requirements

SB 1211 states that property owners of multi-family lots can convert parking lots into living spaces, and replacements for these uncovered parking spaces do not have to be provided.

Standardization of Livable Space

This bill also defines what a “livable space” is when it comes to ADUs, stating that an ADU built on a multi-family property must contain a space for living, eating, cooking, sleeping, and sanitation, though these spaces do not necessarily have to be separate rooms.

AB 2533 – Legalization of Unpermitted ADUs

For primary residences with an unpermitted ADU, AB 2533 offers a path to permitting without penalty.

Permit Relief

Homeowners with an unpermitted ADU on their property can apply for a permit without the automatic rejection due to building code violations, so long as the ADU was built before January 1, 2020 and public health is not at risk.

Transparency and Support

To encourage homeowners to permit these structures, AB 2533 requires that local agencies inform homeowners about their rights and provide easy-to-understand checklists for compliance. It also allows for confidential third-party inspections of the unpermitted structure to be done before applying for permits.

Fee Waivers

AB 2533 does not allow local agencies to impose impact fees or utility connection fees retroactively on unpermitted ADUs. This is done to decrease the fear of financial burden and encourage more owners of unpermitted structures to come forward.

SB 1077 – Coastal Zone Development

Previously, building an ADU or JADU in a coastal zone was difficult to accomplish, as the environmental sensitivities of these areas often prevented this kind of development. However, SB 1077 seeks to change that.

Streamlined Coastal Permitting

According to SB 1077, by July 2026, the California Coastal Commission must provide guidance to local governments as to how they can facilitate ADU development in these sensitive areas.

Public Engagement

Before governments can officially determine their regulations, at least one public workshop must be held to gather community input.

Upcoming laws like SB 1211 could reshape housing opportunities, allowing multi-family properties to build up to 8 ADUs and convert parking spaces into livable units.

Get Expert Help with Your ADU Project

At Better Place Design & Build, we encourage all homeowners to dream big when designing their ADU while also acknowledging the size limits, zoning requirements, setback requirements, and development costs associated with building an ADU in their city. If you’re part of a homeowners association, you must also be mindful of any rules or regulations in your HOA agreement.

Understanding all the latest laws and restrictions can feel overwhelming, as they’re prone to change – especially as ADUs continue to grow in popularity. This is where an experienced ADU builder can step in and be a resource. It’s our job to understand the latest ADU laws and explain them to homeowners clearly.

We make sure your ADU can be completed on time, on budget, and without unnecessary stressors or hassles.

See what’s possible by scheduling your free consultation.