Building an ADU in California

Know your ADU requirements before you build

ADUs you can build in California

These are the types of ADUs that you can build on residential properties
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Junior Accessory Dwelling Unit (JADU)
A Junior ADU (JADU) is an ADU of no more than 500 square feet. A JADU must be within a proposed or existing single-family home or accessory structure, such as a garage.

Unlike ADUs, JADUs may share a bathroom with the single-family home and must only meet “efficiency kitchen” requirements.
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Accessory Dwelling Unit (attached / detached)
Detached ADUs are located in free-standing buildings that are separate from the main single-family home or multi-family building.

Attached ADUs involve adding on to a single-family home.

ADUs are typically no more than 1,200 square feet.
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Conversion ADUs
Conversions are constructed by converting part of an existing single-family or multi-family home, or by converting all or part of an accessory building (like a garage, shed, or studio). This includes garage conversions.
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Tiny Home on Wheels (THOW)
Description coming soon
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Duplex / Triplex
Description coming soon

The ADU rules

Know everything before you build
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Setbacks
Detached ADUs are located in free-standing buildings that are separate from the main single-family home or multi-family building.

Attached ADUs involve adding on to a single-family home.
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Square Footage
The max size of an ADU is determined by the size of the primary dwelling on the property. For single-family homes, the max allowable size for an attached ADU is 50% of the existing living area of the primary dwelling, up to a maximum of 1,200 square feet. For detached ADUs, the maximum size is 1,200 square feet regardless of the size of the primary dwelling.
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Height
Generally, you should be able to build an ADU that’s at least one-story and 16 feet in height. Depending on your residential zoning code, you may be able to build two stories
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Parking
Generally, conversion ADUs and junior ADUs don’t require any parking. Attached and detached ADUs will require 1 parking space, unless your project qualifies for an exemption from the parking requirements.
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Number of ADUs allowed
If you have a single-family home, you can for the most part have one or two ADUs on it. The number of ADUs allowed on multi-family properties depends on the type of ADU constructed and how many dwelling units are already on the property.
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Minimum Lot Size
The good news is that your property can be any size and be eligible for an ADU. There are no minimum lot size restrictions.
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Allowed locations
Generally, you can have an ADU on your property if residential uses are allowed on it, although exceptions may apply. Also, you must have an existing or proposed single-family home on your property or an existing multi-family building (which is a fancy way to say a duplex, triplex, or other type of apartment or condo building).
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Renting the ADU
Yes, your ADU can be rented out, although most cities don’t allow short-term rentals of ADUs. This means you can probably only rent your ADU out for a period of month or longer.

Generally, the property owner will only have to live on the property if a JADU is built on it.
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Duplex and Triplex
You may be able to build based on how your property is zoned. You’ll need to call your local zoning department to confirm.

Select your city to learn more ADU building

More cities coming soon