Bought a House With an Unpermitted ADU? Here's What to Do Next

You're Not the First Owner to Face This

Finding out after closing that a property has an unpermitted ADU — whether it turned up during a title search, an inspection, a refinance appraisal, or just a neighbor's comment — is a common situation for California homeowners. It's unsettling, but it's also a solvable one. The unit's permit status is tied to the property, not to who happens to own it, and California law now includes a specific pathway that may apply to your situation.

Does It Matter Who Built It?

Generally, no — not for purposes of whether the unit can be legalized. California's Assembly Bill 2533 (Government Code Section 66311.7), effective January 1, 2025, extends amnesty-style protections to qualifying unpermitted ADUs and JADUs based on when the unit was built, not who built it or who currently owns the property. If your new home's unpermitted ADU was constructed before January 1, 2020, this law may directly apply to you as the current owner.

What AB 2533 Could Mean for You

For a qualifying ADU or JADU built before January 1, 2020, California law generally provides:

• A local building department generally cannot deny a legalization permit solely because the unit doesn't meet current building standards or a local ADU ordinance
• An exception applies where correcting a violation is necessary because the structure would otherwise be considered substandard under state health and safety standards
• Impact fees and utility connection or capacity charges are generally not required, except where infrastructure upgrades are needed for health and safety compliance
• The local agency cannot penalize you for the unit having been unpermitted before you applied
• You may optionally obtain a confidential third-party code inspection before submitting an application, to get a sense of what a formal review would find

Not every unpermitted ADU qualifies, and individual jurisdictions administer their own application process under this law — an initial review of your specific property is the only way to know how it applies to you.

If the ADU Was Built After January 1, 2020

If the unit doesn't qualify for AB 2533 — most commonly because it was built more recently — it would typically go through your city or county's standard retroactive (sometimes called "as-built") permitting process instead. This generally means the structure is evaluated against current building code rather than the code in effect when it was built, and the specific steps depend on your jurisdiction. See our guide on getting a permit for an ADU that's already built for more on how that process generally works.

Practical First Steps

• Pull the property's permit history to confirm what is and isn't on record with the city or county
• Note the approximate construction date of the ADU, if known — this affects which legalization path applies
• Request an initial property review before making any changes to the structure
• Hold off on renting the unit out or relying on it for insurance/financing purposes until its status is clarified

Common Questions

How Legal ADU Pro Can Help

Legal ADU Pro helps California homeowners understand a newly-discovered unpermitted ADU's situation, research its permit history, and coordinate the legalization process — including determining whether AB 2533 or the standard retroactive permit path applies. We are not a law firm, licensed architect, licensed engineer, or licensed contractor, and we do not guarantee any permit approval or outcome.