Legalizing an unpermitted ADU built before 2020

Which units qualify

The rule covers an unpermitted ADU or junior ADU that was constructed before January 1, 2020.¹ The date is about when the unit was built, so evidence of age is the first thing to gather: old photographs, utility bills, a lease, an assessor's record or aerial imagery showing the structure in place.

What the city can't use against you

For a qualifying unit, the local agency may not deny the permit on either of two grounds: that the unit violates building standards, or that it doesn't comply with the state ADU rules or a local ADU ordinance.¹ So a garage unit sitting two feet from a fence isn't refused simply for missing the setback.

The edge of the protection

The city keeps one ground for refusal. It may deny the permit if it finds that correcting the violation is necessary to comply with the standards in Health and Safety Code Section 17920.3, which is the state's definition of a substandard building.¹

Find out before you apply

Many owners hold back because they fear that asking the question invites enforcement. The statute speaks to that directly. Cities are required to tell the public that, before applying, a homeowner may obtain a confidential third-party code inspection from a licensed contractor to learn the unit's condition and the likely scope of work.¹

After you apply

Once an application is in, a city inspector may inspect the unit and recommend what is needed to meet health and safety standards. If problems are found, the agency must not penalize you for having had the unpermitted unit, and it must approve the permits needed to correct them.¹

Fees

A homeowner permitting a qualifying unit is not required to pay impact fees or connection or capacity charges. The exception is narrow: where utility infrastructure is required for health and safety compliance and the charge is one the fee section permits.¹

Permit and plan check fees are a different matter and still apply.

A note on section numbers

These rules were in Section 66332 until SB 543 moved them to Section 66311.7 at the start of 2026.¹ City handouts that mention "66332" are describing the same protection.