How large can my ADU be?

Generally, ADUs can range from 150-square-foot efficiency units up to 1,000 square feet. Junior ADUs (JADUs) can be up to 500 square feet. See Local ADU Rules for more details on height, setbacks, and other rules and our Guidebook for more detailed information about important ADU laws.

According to state law, you can at least build up to an 800 square feet ADU, as long as rear and side setbacks are at least 4 feet and it is not above 16 feet tall. In these cases, local regulations like lot coverage, floor area, and some others do not apply. Otherwise, size limits depend on your property and your community's rules.