How large can my ADU be?

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. Otherwise, size limits vary depending on your jurisdiction. Typically the maximum size ranges from 850 sf to 1,200 sf.. No room behind or next to your main home? You can build it in your front yard instead. 

Generally, ADUs can range from 150-square-foot efficiency units up to 1,200 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 Workbook for more detailed information about important ADU laws.