ADU stands for Accessory Dwelling Unit. It is a secondary home built on a single-family or multi-family lot that can be used by aging parents, adult children, or even as a rental to produce income. Also called granny flats, mother-in-law units, back-yard cottages, guest houses and casitas, ADUs have been around for generations. ADUs are now being encouraged to help ease California’s housing crisis by increasing the supply of affordable housing.

Recently, new laws have passed in California to help streamline the permit process and increased flexibility related to building heights, setbacks , parking and renting of A-D-Us to add capacity in single family neighborhoods while retaining neighborhood character. These laws make it easier for property owners to add a second unit and expand housing options in already “built-out” communities. ADUs include provisions for living, sleeping, eating, cooking and sanitation. There are four types of ADUs:

Detached ADU – A detached ADU is built separate from the property’s primary structure. It can be up to 850 square feet for a studio and one-bedroom unit or up to 1,000 square feet with two or more bedrooms.

Attached ADU – This type of ADU is built attached to the primary structure with its own entrance. It can be up to 850 square feet for a studio and one-bedroom unit or up to 1,000 square feet with two or more bedrooms.

Converted Existing Space ADU – Converting an existing space or structure on the lot into a livable unit is a Converted Existing Space ADU. This could be a garage, attic or detached accessory structure that includes provisions for living, sleeping, eating, cooking and sanitation.

Junior ADU – A Junior ADU is the conversion of existing space that is contained within the existing single-family residence. They can be 500 square feet, or smaller and have a dedicated entrance. But it does not have to have its own bathroom.