Thousands of Southern California homes have a converted garage or backyard unit that was never permitted. For years, coming forward meant risking fines or demolition. California law now offers a much clearer path, especially since AB 2533 took effect on January 1, 2025.
This guide summarizes Government Code section 66332 as amended by AB 2533 and explained in HCD's ADU Handbook. It's general information, not legal advice.
What AB 2533 changed
Before 2025, state law protected unpermitted ADUs built before January 1, 2018. AB 2533:
- Extended protection to units built before January 1, 2020.
- Added JADUs to the protection.
- Narrowed the grounds for denial. A local agency can deny a permit to legalize a qualifying unit only if it finds that correcting the violation is necessary to comply with the substandard-building standards in Health and Safety Code section 17920.3. Before, the standard was a general health-and-safety finding.
- Barred penalties. Agencies can't penalize you for having built without a permit, for example by doubling permit fees.
- Limited fees. Impact fees and connection or capacity charges generally can't be imposed unless a utility connection is needed to fix a section 17920.3 condition.
- Required public information. Agencies must post a checklist of the section 17920.3 conditions and tell owners they may get a confidential third-party inspection from a licensed contractor before applying.
The Association of Bay Area Governments and LA County Regional Planning have published summaries of these changes. LA County's staff memo confirms they took effect January 1, 2025.
What section 17920.3 covers
Health and Safety Code section 17920.3 lists conditions that make a building "substandard." Examples include:
- inadequate sanitation or lack of hot and cold running water
- structural hazards
- hazardous electrical wiring or plumbing
- faulty weather protection
- fire hazards and inadequate exits
Your unit doesn't have to meet today's building code in every detail. It must not be substandard under these criteria. If it is, you'll need to fix those specific conditions.
Step-by-step: legalizing an unpermitted ADU
- Gather evidence of the build date. Look for older photos, utility bills, rental records, aerial imagery or tax records showing the unit existed before January 1, 2020.
- Get a confidential pre-inspection. Hire a CSLB-licensed contractor, or a qualified inspector, to walk the unit against the section 17920.3 checklist before you contact the city.
- Fix the obvious hazards first. Address smoke and carbon-monoxide alarms, exposed wiring, egress windows and water heater strapping.
- Prepare as-built plans. A designer documents the existing unit. Some cities have simplified as-built processes.
- Apply for a permit under your city's unpermitted ADU or ADU legalization program, citing Government Code section 66332.
- Inspection. The city inspects, and it may open walls in limited areas to verify conditions.
- Corrections and final. Complete the required corrections and receive a final sign-off.
What if the unit was built after 2019?
Section 66332's protections don't apply. You can still apply to permit the unit as a new ADU, but it must meet current code and standards. That often means more work, such as opening walls, adding energy upgrades, and possibly fees. Many units can still be legalized this way.
Is it worth legalizing?
Usually, yes:
- Safety: you and your tenants are protected from hidden hazards.
- Insurance: unpermitted units can complicate claims.
- Sale: buyers and lenders increasingly flag unpermitted space, and it can reduce your price or kill deals.
- Rental income: a legal unit can be rented with fewer legal risks, and its income may count toward loan qualification with some lenders.
- Tax: adding permitted space can trigger a reassessment of the new construction value. Ask your county assessor how legalization is treated.
Working with a contractor
Choose a contractor experienced with legalization. It's a different skill from new construction. Ask:
- How many unpermitted ADUs have you legalized in my city?
- Do you prepare as-built drawings, or partner with a designer?
- Will you do a confidential pre-inspection report?
Our directory flags builders with a confident CSLB license match. Always confirm licenses at cslb.ca.gov.
Garage conversions and replacement parking
If your unpermitted ADU is a converted garage, state law bars requiring replacement parking for the lost garage spaces. SB 1211 (2025) extended this to uncovered spaces. See our garage conversion guide.
Frequently asked questions
Can I legalize an unpermitted ADU in California?
Often yes. Under AB 2533, effective January 1, 2025, ADUs and JADUs built before January 1, 2020 can be denied only if correcting a violation is necessary to meet the substandard-building standards in Health and Safety Code section 17920.3.
Will I be fined for an unpermitted ADU if I apply to legalize it?
AB 2533 bars local agencies from penalizing applicants for having built without a permit, such as by charging double fees, for qualifying units.
Does my unpermitted ADU have to meet current building code?
For qualifying pre-2020 units, the key test is whether the unit is substandard under Health and Safety Code section 17920.3, not full compliance with today's code.
Can I get an inspection before I contact the city?
Yes. Agencies must tell owners they may obtain a confidential third-party inspection from a licensed contractor before applying.
This page is general information, not legal, tax or financial advice. Costs vary by property and builder. Images are AI-generated illustrations. Last updated November 2026.