San Francisco, CA Accessory Structures: Garage Conversions (2026)

an ADU shall be constructed (i) entirely within the buildable area of an existing lot, provided that the ADU does not include a vertical addition, or (ii) within the built envelope of an existing and authorized detached garage, storage structure, or other detached structure on the same lot. For purposes of this subsection 207.1, a “detached” structure or ADU shall not share structural walls with either the primary structure or any other structure on the lot. For purposes of this subsection 207.1, the “built envelope” shall include the open area under an existing and authorized cantilevered room or room built on columns; decks, except for decks that are supported by columns or walls other than the building wall to which they are attached and are multi-level or more than 10 feet above grade; and lightwell infills provided that the infill will be against a blank neighboring wall at the property line and not visible from any off-site location; as these spaces exist as of July 11, 2016. An ADU constructed entirely within the existing built envelope, as defined in this subsection 207.1, along with permitted obstructions allowed in Section 136(c)(32), of an existing building or authorized detached structure on the same lot, or where an existing detached garage or storage structure has been expanded to add dormers, is exempt from the notification requirements of Section 311 of this Code. If the existing building or authorized detached structure on