What size ADU is allowable in San Diego?

An ADU is intended to be secondary in size to the single-family residence. An ADU attached to a primary dwelling may be up to 50% of the size of the single-family residence, up to a maximum of 1,200 square feet. An ADU detached from the single-family residence may be up to 1,200 square feet, regardless of the size of the residence.

To find out how your property is zoned (please enter your APN # on the upcoming screen)
Complete List of ADU Zoning Requirements
Instructions for Obtaining a Building Permit