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  • Writer's pictureADU Builders Group

Multiple ADUs: Boosting California Homes

Updated: Dec 8, 2023

Did You Know You Can Build Three ADUs on a Single-Family Property in California?

California has been at the forefront of promoting innovative housing solutions to address its growing housing crisis. Exciting news! The government has relaxed rules for ADUs, giving homeowners more choices to increase housing availability. In California, you can now build up to three ADUs on one property, instead of just one or two. Let's explore this game-changing update in housing policy.

1. Primary ADU

The first ADU is often referred to as the primary ADU and is typically a self-contained unit that can be attached to or detached from the main dwelling. This can be a granny flat, an in-law unit, or a standalone tiny house. The rules and regulations for primary ADUs have been significantly relaxed, making it easier for homeowners to build them.

2. Junior ADU (JADU)

In addition to the primary ADU, California also allows for the construction of a Junior ADU (JADU). A JADU is a smaller, more compact unit that can be created within the existing living space of the primary dwelling or as an addition to it. JADUs are a fantastic option for homeowners who have unused spaces, like a spare bedroom or converted garage, which can be turned into a rental unit.

3. Second ADU (Detached or Attached)

The third ADU on the property can either be detached or attached to the primary dwelling. The second ADU is also called the "second junior accessory dwelling unit." It allows homeowners to make more money or have more housing choices. This unit can be built in addition to both the primary ADU and the JADU, effectively allowing three separate living spaces on the same property.

Benefits of Having ADUs

Discover the benefits of different ADU types and the wide range of people who can gain from residing in them.

1. Detached ADUs

Privacy and Independence

Detached ADUs are standalone structures, providing residents with a private living space. This level of independence is perfect for multigenerational families, adult children, or even homeowners looking to generate rental income.

Rental Income

Homeowners can significantly boost their income by renting out a detached ADU. This can help offset the mortgage or other housing-related costs, making homeownership more accessible.

Increased Property Value

Detached ADUs often increase the overall value of the property. These additional living spaces can make your home more attractive to potential buyers, providing a long-term financial benefit.

2. Junior ADUs (JADUs)


JADUs are typically smaller than traditional ADUs, making them an affordable housing option. They are perfect for individuals or couples who are looking for a more budget-friendly place to live.

Aging in Place

Older homeowners can consider JADUs for aging in place. They can move into the JADU while renting out their primary residence to generate additional income.

Reduced Environmental Impact

JADUs are often designed with energy-efficient features, which can lead to lower utility costs, reduced carbon footprint, and overall sustainability.

3. Garage Conversions

Utilizing Existing Space

Garage conversions repurpose underutilized space, providing homeowners with additional square footage without needing to build a new structure.


Garage conversions can serve various purposes, from additional living space to a home office, gym, or a rental unit.

Community Integration

Converting garages into living spaces helps foster a sense of community, as they often allow for more efficient land use and less urban sprawl.

Who Benefits from Living in These ADUs?


Detached ADUs are ideal for accommodating extended families or providing adult children with a place to live while maintaining some independence.


JADUs can enable seniors to downsize while staying close to family, maintaining social connections, and enjoying a more manageable living space.

Young Professionals

Garage conversions can serve as affordable housing for young professionals, allowing them to live close to work or amenities.


ADUs can offer college students an independent living space near their campus, providing a quieter and more focused environment for studying.


Homeowners can invest in detached ADUs, generating rental income that can help cover the costs of their primary residence or serve as a standalone investment property.

Frequently Asked Question

Here are FAQs and answers about adding multiple ADUs in a single-family residence, based on the updated ADU Handbook Update as of July 2022.

Ministerially Approved ADUs and Junior ADUs (JADUs) Not Subject to Local Standards

• Are local agencies required to comply with Government Code section 65852.2, subdivision (e)?

Yes. All local agencies must comply with subdivision (e). This subdivision requires the ministerial approval of ADUs within a residential or mixed-use zone. The subdivision creates four categories of ADUs that should not be subject to other specified areas of State ADU Law, most notably zoning and development standards.

For example, ADUs under this subdivision should not have to comply with lot coverage, setbacks, heights, and unit sizes. However, ADUs under this subdivision must meet the building code and health and safety requirements. The four categories of ADUs under subdivision (e)(1) are:

(A) One ADU and one JADU are permitted per lot within the proposed space of a single-family dwelling or existing space of a single-family dwelling or accessory structure that meets specified requirements such as exterior access and setbacks for fire and safety.

(B) One detached new construction ADU that does not exceed four-foot side and rear yard setbacks. This ADU may be combined on the same lot with a JADU and may be required to meet a maximum unit size requirement of 800 square feet and a height limitation of 16 feet.

(C)Multiple ADUs within the portions of multifamily structures that are not used as livable space. Local agencies must allow at least one of these types of ADUs and up to 25 percent of the existing multifamily structures.

(D)Up to two detached ADUs on a lot that has existing multifamily dwellings that are subject to height limits of 16 feet and four-foot rear and side yard setbacks.

The above four categories may be combined. For example, local governments must allow (A) and (B) together or (C) and (D) together.

The most common ADU that can be created under subdivision (e) is a conversion of proposed or existing space of a single-family dwelling or accessory structure into an ADU, without any prescribed size limitations, height, setback, lot coverage, architectural review, landscape, or other development standards. This would enable the conversion of an accessory structure, such as a 2,000-square-foot garage, to an ADU without any additional requirements other than compliance with building standards for dwellings.

These types of ADUs are also eligible for a 150-square-foot expansion (see discussion below).

ADUs created under subdivision (e) shall not be required to provide parking if the ADU qualifies for one of the five exemptions listed under subdivision (d). Moreover, these units shall not, as a condition for ministerial approval, be required to correct any existing or created nonconformity.

Subdivision (e) ADUs shall be required to be rented for terms longer than 30 days and only require fire sprinklers if fire sprinklers are required for the primary residence. These ADUs shall not be counted as units when calculating density for the general plan and are not subject to owner occupancy


California is allowing homeowners to build up to three additional dwelling units (ADUs) on their property. This is helping to address the housing crisis and provide more housing options. This helps property owners and also helps make more homes available and affordable in the whole state.

Knowing the rules for building multiple ADUs on a California property is important. These regulations cover zoning, lot size, setbacks, parking, and more. To start, homeowners should ask local authorities or a professional to ensure they follow all the rules.


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