There are two types of attached ADU’s.

1. Junior ADU’s (JADU) are commonly defined as being under 500 square feet. Minimum size in California is 150 square feet. Individual cities have their own definitions and regulations which can define this. A JADU can be a garage conversion, or a new addition to the house. In most cases, owner occupancy is required in either the main house or the JADU. It is possible to also have a detached ADU in addition to an attached JADU, and the home owner can live in any of the three units. ADU’s under 750 feet are exempt from local impact fees.

2. Standard ADU’s that are attached can be larger than 500 square feet. In most cities they cannot be larger than 50% of the main house. Check local requirements for minimum bed/ bath count in relation to overall size of your ADU.