Honolulu started waiving up to $10,000 in traditional home construction fees for ADUs in 2015. Since then 150 permits have been issued, and preliminary paperwork has been started on another 1,200 applications, said Eileen Lacaden, community and development specialist with the Hawaiʻi Appleseed Center for Law & Economic Justice.

But more work needs to be done on issues such as parking and sewer capacity to ensure that more Oʻahu properties can accommodate ADUs, said Council Chairman Ron Menor, who introduced the concept before the City Council in 2015.