"Some people think of an ADU as a tricked-out garage but it's a house with a garage underneath — a two-story home — just small." Building one similar in size to Iverson's costs about $250,000.

When Korean architect Hyun-Wook Lee adopted a simple duplex design that he had learned in Vancouver, and gave it the novel name of “peanut house,” he changed more than the way Koreans build homes.