How to get permits for an ADU built without them

California is in the midst of a building boom for accessory dwelling units, which accounted for almost one-fifth of the housing units permitted and built in 2022.

The number of unpermitted ADUs already in existence is jaw-dropping too.

Studies done between 2010 and 2020 found that 11% to 66% of the single-family homes in selected parts of Los Angeles, Oakland and Berkeley had unpermitted units. In fact, one researcher who examined the communities between Long Beach and downtown Los Angeles found that more than 75% of the housing units added between 1991 and 2010 were unpermitted. A UCLA professor estimated in 2018 that Los Angeles had at least 50,000 unpermitted secondary units on single-family lots.

Unauthorized ADUs proliferated in large part because many California cities made it well-nigh impossible to get permits for them. Those barriers did nothing to reduce the demand for living spaces, particularly from lower-income households whose members spanned multiple generations. “If people don’t have housing, they will create housing for themselves and their families,” said Renée Schomp, former director of the Napa Sonoma ADU Center.

But owning an unpermitted ADU carries risks, especially if you rent it out. You’ll face fines, insurance problems and, potentially, lawsuits from tenants.

The incentives for complying may not be enough, though, to persuade you to get the necessary permits. It can take almost as long to get them as it would for a new ADU, and the cost of bringing your unit into compliance can be quite high.

That’s because unpermitted ADUs can have hidden problems in their foundation, framing, wiring and plumbing that can be expensive to fix. “If it’s a gorgeous unit, that doesn’t mean anything,” said Avi Levi of Levi Design Build, a developer who does most of his work these days on ADUs.

Common compliance issues

One reason people build dwelling units without permits is that the time-consuming process of getting approvals can raise a project’s price tag by thousands of dollars. But with no inspectors to ensure that the work complies with city codes, nothing stops a contractor from falling short of the local standards — inadvertently or not.

“People don’t get it,” Levi said. “When they’re doing work without a permit, they’re basically letting the person that did the job get away with whatever they wanted to get away with.”

Steven Frasher, spokesman for L.A. County Public Works, offered a list by email when asked what problems the county’s inspectors observed most often. “Improper exiting, improper venting of heating devices, undersized wiring, or improper electrical grounding, to name a few, can lead to life safety issues that are both long-term [chronic] or short-term [acute] exposure risks,” Frasher said. “Most people are aware of acute risks such as fire, but they tend to not pay enough attention to the chronic risks such as headaches, nausea, and breathing problems can be caused by unpermitted building materials, poor ventilation, and mold caused by improper construction methods.”

And even if the contractor did everything by the book, that may not be enough to bring your unit into compliance years later. Although a state law passed in 2018 allows local officials to judge your ADU by the building codes that were in place when it was built, they have the discretion to insist that you upgrade to newer, more stringent standards.