In San Francisco, "ADU" refers to a new unit inside the existing building envelope. An example of an ADU would be a first floor garage converted into an apartment. The apartment would be an ADU.
In most parts of the country, "ADU" also refers to a backyard unit.
Contributed by 
LocalWiki is a grassroots effort to collect, share and open the world’s local knowledge. We are a 501(c)3 non-profit organization.
Except where otherwise noted, this content is licensed under a Creative Commons Attribution License. See Copyrights.
