California Accessory Dwelling Unit (ADU) Guide

What is an accessory dwelling unit?

An accessory dwelling unit (ADU) is defined as an additional living space to a property that:

• Can be detached or attached to the property
• Is located on the same lot as a property
• Contains facilities that allow for adequate living independent of the main property (kitchen, bathroom, bed, etc.)

These units can be built from scratch, but it is more common for ADUs to be converted from something else, such as a detached garage or a large shed.

Junior ADUs are classified separately from ADUs, as they are not required to have their own bathroom/sanitation facilities, and they also must be less than 500 square feet.

Can I build an accessory dwelling unit on my property?

If you own a house, then you can build an ADU on your property if you so choose. Neither your HOA or your municipal government can bar you from building an ADU thanks to recent legislation aimed to boost the amount of housing available. Keep in mind that this only applies to owners of houses, and HOAs can still regulate the construction of ADUs in condominium complexes.

While California homeowners can freely build ADUs, most municipalities subject these dwellings to regulation and have a rigid permit process in order to construct one. In order to get a permit, you will have to submit an application with your local government, that typically requires a detailed site plan and safety precautions of the project.

Once I build an ADU, what regulations is it subject to?

Renting out your ADU is legal in California for long-term rentals, but for short-term rentals of less than 30 days (Airbnb), many HOAs will strictly prohibit them. All rental restrictions that would apply to the main property will also apply to an ADU.

A local government or HOA may limit the maximum size of an ADU, but may not make this maximum less than 850 square feet., or less than 1,000 square feet for those with more than 1 bedroom. They must also allow the maximum height to be up to 16 feet at least.