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Accessory Dwelling Unit


What is an ADU? What are the types of ADUs? And What are the benefits of building an ADU in your backyard?

Avivit Katzir                                                                                                      2020-11-30

According to California’s Department of Housing and Community Development, the housing production is not keeping pace with the demand. In the last decade, less than half of the homes needed to keep up with the population growth were built. Additionally, new homes are often constructed away from job-rich areas. This lack of housing that meets people’s needs is impacting affordability and causing average housing costs, particularly for renters in California, to rise significantly. As affordable housing becomes less accessible, people drive longer distances between housing they can afford and their workplace or pack themselves into smaller shared spaces, both of which reduce the quality of life and produce negative environmental impacts. 

Existing California laws have always permitted the construction of secondary units. However, for decades, local ordinances have made it difficult for homeowners to build new units. Imposed standards at the city and county level regulated parking, setbacks, lot size, lot coverage, and required substantial fees.

In an effort to address California’s housing crisis, the State of California passed new legislation ( SB 1069 , AB 2299 and AB 2406 ) in September 2016 which gave homeowners the right to develop Accessory Dwelling Units (ADUs) on most single-family residence properties, effectively doubling the housing potential of these residences. Local governments were required to adopt updated, ADU ordinances in accordance with these new state requirements by January 1, 2017.

In January 2020, more State Bills (SB 1069, AB 2299, SB 229, AB 494, AB 68, SB 13, AB 881) came into effect which made it even easier to build Accessory Dwelling Units in California. These bills invalidate local ADU ordinances across the state and replace them with state-mandated rules unless the local jurisdiction adopts an ADU ordinance that is at least as permissible as the state-mandated rules. For more details on the new rules, read our ADU STATE REGULATIONS blog.

So What is an ADU?

An ADU, (Accessory Dwelling Unit), is a second residential structure, built on the same property as a single-home residence, or multi-family,  and serves as an independent living facility for one or more persons.

ADUs are also known by other names such as Granny Flat, In-Law Unit, Ohana Unit, or Companion Unit, and more. In order to be classified as an ADU, the unit must come fully equipped with at least one full bathroom and one full kitchen.

An ADU must also conform to all State,  Local City, and Planning code requirements, as well as energy and building code requirements established by California Title 24 Building Energy Efficiency Standards and Housing and Community Development CALGreen compliance.

Types of Accessory Dwelling Units

There are four types of ADUs depending on how it is built in relation to the existing primary residence on your property. Two are placed outside of the main residence and two are within the main residence.

• DETACHED: The unit is a stand-alone structure separate from, and with no common walls, to the primary dwelling. It may be built on top of a detached garage.

• ATTACHED: The unit is an addition on the side, rear or top of the main residence, sharing a wall (but no access) with the primary structure.

• CONVERTED EXISTING SPACE: Converting a space within the existing floor area of the primary residence or other existing accessory structure on the property (e.g. master bedroom, attached garage, attic, or basement) that is converted into an independent living unit.

• JUNIOR ACCESSORY DWELLING UNIT (JADU): A specific type of conversion of existing main residence space that is contained entirely within an existing single-family residence (similar to an attic or a garage).  Like other ADU units, it requires a separate entrance. The main differences between an ADU and JADU are:

  • Size: May not exceed 500 sq. ft. and contained entirely within the existing walls of the single-family dwelling
    • Bathroom: May include a separate sanitation facility or share one with the existing main dwelling
    • Kitchen: Must meet the “Efficiency Kitchen” requirements, meaning plug-in appliances and not a full kitchen
    • Accessibility: Can have access to the main residence
    • Parking: Does not require new parking

Why build an ADU

ADUs can serve as multiple uses depending on one’s needs, which can change over time.

Increase Property Value: Building an ADU immediately increases the overall value of your property.

Passive Income: With the continuous housing shortages, an ADU is a great way to supply housing to renters. Having an ADU                              allows you to generate a supplementary income. Either by renting out the ADU or it opens the option for homeowners to move                            into the ADU and rent out the main residence when they’ve decided to retire.

Affordable housing: ADUs is an affordable home to build in California as they help increase communities’ housing supply at a much cheaper cost. This creates a lower cost, more affordable housing option to meet the needs of existing and future residents in job-rich areas.


Additional independent space for you or your loved ones to use: Building an ADU can provide a home for a loved one needing assistance. Whether it’s an elder that you want to live close by, or for your child after graduating from college, or a young couple to start and establish independence and save for future home buying.
With today’s reality, WFH has become the norm. An ADU can offer a space to the working adult, the artist who needs extra space, or the child that needs to attend school virtually.


As you can see there are a lot of different types of ADU’s that can serve as multiple uses and offer added value to your property. We hope this piece was useful and gave you some knowledge of the ADU world. 


When you are ready to add value to your property and build your own ADU, please visit akdhomes.com/contact us to schedule a free consultation with our ADU experts. 



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