How Many ADUs Can You Have on Your Property in California?

Understanding California’s ADU Regulations

The state of California dictates that there may be up to 3 dwellings on a single-family residential lot. These dwellings can include 1 single-family residence, 1 accessory unit, and 1 junior accessory unit.

Traditional accessory buildings can be as large as 1200 square feet, though many municipalities have lower maximum limits than this. When it comes to junior accessory dwellings, the maximum size is 500 square feet.

Start your ADU project with a feasibility study to understand local size limits, setbacks, and utility connections—early planning prevents costly surprises later.

Standard ADU Vs. Junior ADU Comparison

When it comes to ADUs vs JADUS, most people think that “junior” simply implies that the unit is smaller, and though this can be the case, size is not actually what defines a JADU.

An ADU is an independent living structure built on the same lot as an existing home. It can be attached to the main home, creating an attached ADU, or it can be a completely detached, separate unit. In either case, it is new construction and can be as small 150-220 square feet or as large as 1200.

Junior Accessory Dwelling Units reallocate existing space within the home to create a separate living space So, while the exterior footprint of the house does not change, it has still been transformed into a multifamily home.

Other key differences between an ADU and a JADU include:

How Many ADUs Can You Build on a Single Property?

Assembly Bill 68 was created to increase affordable housing options and says that a single property can contain up to 3 independent dwelling units. These 3 separate units include:

• The primary structure, which is oftentimes the lot’s original single-family home
• An ADU, which can either be a detached or attached unit
• A JADU, or junior accessory unit

Key Regulations for Building Both an ADU and JADU

Along with individual city building codes, you also need to understand the regulation differences when it comes to building multiple ADUs on a single-family residential property as opposed to a multi-family structure.

Accurate, detailed plans are essential for seamless approval of ADU and JADU permits—work with experienced designers to streamline the process.

Single-Family Residential Properties

Here are key regulations to consider if you are the owner of a single-family residence looking to add multiple ADUs to your property.

Number of Units

On single-family lots, you can build 1 ADU and 1 JADU in addition to the main dwelling.

JADU Location

A JADU must be within the primary residence. This could involve converting an existing part of the house, such as a spare bedroom and a garage, into a separate living space, so long as it does not exceed 500 sq ft.

ADU Location

The ADU can be detached or attached and is allowed to be up to 1,200 sqft. If the ADU is attached, it cannot exceed 50% of the size of the primary dwelling.

Owner Occupancy

For properties with a JADU, the homeowner is required to live on-site, either in the main residence or the JADU.

Parking Requirements

Parking spaces are not required for ADUs under certain conditions, such as proximity to public transit. JADUs don’t require additional parking​.

Multi-Family Residential Properties

Multi-family structures are apartment buildings, condos, townhomes, and triplexes. If you are the owner of a multi-family property, you can add ADUs, though the restrictions differ from residential properties.

Number of Units

Multi-family properties allow for up to 2 detached ADUs. Additionally, existing non-habitable spaces (e.g., garages, basements, storage rooms) can be converted into ADUs, with the total number of ADUs allowed up to 25% of the existing units.

Bonus ADUs

In areas classified as Transit Priority Areas (TPAs), more ADUs can be built if the property owner provides deed-restricted affordable housing. There’s no cap on the number of bonus ADUs in such areas​.

Comparison Chart: Number of ADUs Allowed in Greater San Diego

What is the SB9 Rule in California?

The SB9 rule allows owners of single-family properties to split their lot to allow for more units to be built on the property. However, there are limits on who can implement SB9. Homes located in a San Diego county historic district, for example, cannot split their lot.

If you are curious about whether SB9 applies to your home, contact your building department.

SB9 lot splits can turn underutilized properties into housing solutions—consult a professional to explore opportunities without disrupting neighborhood aesthetics.

How to Maximize ADU Potential on Your Property

You don’t need to have a huge lot to maximize your property’s ADU potential. We encourage homeowners to consider unused spaces within their home, like guest bedrooms, secondary living spaces, or basements, as potential JADUs, so long as they can accommodate a separate entrance.

When it comes to traditional ADUs, garage conversions are often a cost-effective build, while 2-story ADUs will maximize your total square footage while minimizing the footprint on your property.

Don’t overlook vertical space—adding a second story to an ADU can significantly increase usable square footage while maintaining a smaller footprint.

Financial and Legal Considerations

The financial implications of building multiple ADUs on your property extend beyond construction costs and the payments associated with financing options. You also have to consider your property taxes and how adding rental units or in-law suites might impact that.

In terms of logistical and legal considerations, you must consider your local zoning regulations, rental laws, and restrictions placed by your homeowners association.

An experienced ADU builder can walk you through all these considerations before submitting your ADU permit application so you can feel prepared and confident about moving forward.

Before breaking ground, budget for construction, taxes, and future maintenance—thorough financial planning ensures your ADU remains a profitable investment.

Ready to Build Your ADU?

Whether you are looking to build one ADU or multiple ADUs on your property, Better Place Design & Build can help. Our free consultation will not only walk you through the potential costs and construction process but also help you pinpoint areas of your home that could be repurposed into an ADU or JADU, showing you possibilities you didn’t even know where there.