If you are adding square footage onto an existing structure to create an attached ADU, the square footage of the ADU cannot exceed 50% of the square footage of the main residence or 1,000 square feet, whichever is less; however, an ADU of up to 800 square feet is always allowed.
Examples:
- 2,200 square-foot main residence à 1,000 square-foot ADU allowed
- 1,800 square-foot main residence: à 900 square-foot ADU allowed
- 1,500 square-foot main residence: à 800 square-foot ADU allowed
- 1,000 square-foot main residence: à 800 square-foot ADU allowed
If you are building a new structure that is separate from the existing main residence to create a detached ADU, the square footage of the ADU cannot exceed 1,000 square feet.
If you are converting existing space into an ADU, there is no limit on the size of the ADU.
If you are constructing a JADU through internal conversion of a single-family residence, the square footage of the JADU cannot exceed 500 square feet.