State law says an ADU permit cannot be denied due to nonconforming zoning, building code violations or unpermitted structures unless there is a threat to public health or safety, and they are not affected by building the ADU.

Existing unpermitted ADUs can go through the permitting and approval process set out in your County Guidebook. Planning staff will work with you to determine what would be involved to bring your ADU up to code. To note, if you constructed your ADU within the last ten years, you will be required to submit an engineer’s report and a Title 24 Energy Report.

For unpermitted ADUs built before January 1, 2018, state law says a permit to legalize cannot be denied even if there is a violation of ADU laws or building standards, unless it is a “health and safety concern” or if the building is deemed “substandard” by state Health and Safety Code.