78% of San Jose ADUs Have No Permit: California's AB 2533 Amnesty Is the Only Path to Legalization
ADU Pilot Team
ADU Pilot Team
Stanford and MIT researchers used satellite imagery to count backyard structures in San Jose. They found roughly four unpermitted ADUs for every one with a permit. California responded with AB 2533, a statewide amnesty that took effect January 1, 2025. This guide covers who qualifies, what the process costs, and what happens if you do nothing. For the broader regulatory picture, see our complete California ADU law guide. If you are evaluating the financial side, our ADU financing guide covers how legalization changes your lending options.
Bottom Line
If you own an unpermitted ADU or JADU in California that was built before January 1, 2020, AB 2533 gives you a path to legalize it without fines, without impact fees, and without meeting current building codes. Inspections focus on health and safety under a specific state checklist, not full code compliance. You can even get a confidential third-party inspection before applying, without triggering code enforcement.
The financial case is straightforward: an unpermitted ADU contributes $0 to your property's appraised value under Fannie Mae guidelines. A legalized ADU contributes its full market value, often $150,000 to $400,000 or more in California markets. Legalization typically costs $16,000 to $62,000 depending on how much repair work the unit needs. The alternative — doing nothing — risks daily fines, insurance claim denials, and a property that is harder to sell, refinance, or insure.
The Scale of the Problem
Unpermitted ADUs are not rare exceptions. In the only rigorous satellite-based study of an American city, they outnumber permitted ones by nearly four to one.
A 2024 peer-reviewed study published in the Journal of the American Planning Association used satellite imagery and computer vision to identify backyard structures across San Jose between 2016 and 2020. The researchers, from Stanford's RegLab and MIT, found approximately 1,045 unpermitted detached ADUs compared to 291 permitted ones during that period. That means roughly 78% of new detached ADUs in San Jose were built without permits. [1]
The study also found that unpermitted ADUs were concentrated in more diverse, denser, and more crowded neighborhoods. Household income showed no correlation with whether an ADU was permitted, which suggests that the cost of permits is not the primary barrier. The researchers pointed to permit-related fees of $3,000 to $4,700 as one factor, but the complexity and time required for the permitting process appeared to be a larger driver. [1][2]
For homeowners considering the permitted route in San Jose, our San Jose ADU feasibility case study walks through zoning, setbacks, design options, and cost estimates for a real property. San Jose is not unique. A Berkeley city study found that up to 90% of ADUs in that city lacked building and zoning permits as of 2011. [3] The Casita Coalition, which sponsored AB 2533, estimates that "hundreds of thousands" of unpermitted ADUs exist statewide, though no reliable census exists. [4] Earlier research by Wegmann and Mawhorter (2017) found that in the 1990s, California added roughly 37 informal housing units for every 100 legally permitted ones. [5]
AB 2533 targets this existing but invisible housing stock.
What AB 2533 Actually Does
AB 2533 (Chapter 834, Statutes of 2024) amended Government Code Section 66332. It took effect January 1, 2025, and has no sunset provision — this is a permanent change to state law. [6]
The law does four things:
1. Extends the eligibility window. The previous amnesty law (enacted in 2018) only covered unpermitted ADUs built before January 1, 2018. AB 2533 moves the cutoff to January 1, 2020, and adds JADUs to the covered categories for the first time. [6][7]
2. Prohibits fines for having an unpermitted unit. Local agencies cannot penalize a homeowner simply for owning an unpermitted ADU or JADU. If an inspector finds problems, the agency must approve the necessary permits to fix them rather than issuing penalties. [6][8]
3. Eliminates impact fees and connection charges. Homeowners legalizing under AB 2533 cannot be charged development impact fees or utility connection/capacity fees. The only exception: if new utility infrastructure is needed to meet the health and safety standard, connection fees may apply. [6][9]
4. Sets the inspection bar at health and safety, not full code compliance. Inspections use the Substandard Housing Inspection Checklist based on Health and Safety Code Section 17920.3. This checklist evaluates whether the unit has life-threatening deficiencies — not whether it meets every provision of the current building code. [6][10]
The law also guarantees homeowners the right to obtain a confidential third-party code inspection by a licensed contractor before submitting a formal application. This inspection does not trigger code enforcement. [6]
What HSC 17920.3 Actually Checks
The Substandard Housing Inspection Checklist evaluates 12 categories of conditions. A unit can be classified as "substandard" if any single condition reaches a severity threshold that endangers life, health, or safety. [10]
| Category | What Inspectors Look For |
|---|---|
| Sanitation | Functional toilet, sink, shower/tub; hot and cold water; proper sewer connection |
| Heating | Working heating system in habitable rooms |
| Ventilation and light | Adequate natural light, ventilation, or electrical lighting |
| Moisture and mold | Visible mold growth beyond minor surface condensation |
| Pest infestation | Confirmed insect, vermin, or rodent presence |
| Structural hazards | Deterioration, unsafe design, seismic deficiency |
| Fire safety | Adequate exits, smoke and CO alarms, no hazardous material accumulation |
| Improper conversions | Garage or non-habitable space converted without meeting safety requirements |
| Electrical | GFCI/AFCI protection, no exposed wiring, grounded outlets |
| Plumbing | Proper pipe installation and venting |
| Emergency egress | Each bedroom must have an emergency escape window (min 20" wide, 24" high, 5.7 sq ft net opening) |
| Alarms | Working smoke detectors and carbon monoxide alarms |
The standard is whether the condition "endangers the life, limb, health, property, safety, or welfare of the public or the occupants." [10] Cosmetic issues, outdated fixtures, or non-current-code materials are not grounds for denial.
Who Qualifies
| Requirement | Details |
|---|---|
| Construction date | ADU or JADU must have been built or converted before January 1, 2020 [6] |
| Unit type | Must meet the statutory definition of an ADU or JADU under Government Code Section 65852.2 [6] |
| Location | Residential lot in any California city or county [6] |
| Documentation | Proof of construction date (assessor records, escrow documents, historical records, satellite imagery) [11] |
| No demolition order | Cannot have an active court-ordered demolition [6] |
| Applicant | Property owner or authorized representative [11] |
If your unit was built between January 1, 2018 and December 31, 2019, AB 2533 is your first opportunity for amnesty — the previous law did not cover this period. If your unit was built before January 1, 2018, you were already eligible under the prior law, and AB 2533 continues that eligibility. [7]
The 7-Step Legalization Process
The following steps reflect the process as implemented across multiple California jurisdictions. Timelines and costs vary by city. [12][13]
| Step | What Happens | Estimated Cost | Timeline |
|---|---|---|---|
| 1. Initial assessment | Hire a professional to inspect the unit and produce a preliminary report | $500–$1,500 | 1–2 weeks |
| 2. Confidential pre-inspection (optional) | Licensed contractor evaluates the unit against the HSC 17920.3 checklist. Results are private and do not trigger enforcement | Included above | — |
| 3. Document preparation | As-built drawings (floor plan reflecting current conditions), Title 24 energy compliance documentation | $3,500–$9,000 (drawings) + $800–$2,000 (energy) | 2–4 weeks |
| 4. Permit application | Submit to local building department: construction date proof, site/floor plans, utility connection details, fire safety documentation | $2,500–$8,500 (total application fees) | — |
| 5. Plan review | Building department reviews submittal against HSC 17920.3 standards | — | 4–8 weeks |
| 6. Construction repairs | Complete required upgrades: smoke/CO alarms, GFCI outlets, egress windows, electrical panel upgrades, ventilation, heating | $8,000–$41,000 | 4–12 weeks |
| 7. Final inspection | Building inspector verifies all work; Certificate of Occupancy or Compliance issued | — | 1–2 weeks |
Total estimated cost: $15,800 to $62,000. The range depends almost entirely on the condition of the unit. A well-built garage conversion that only needs smoke alarms, GFCI outlets, and an egress window will be at the low end. A unit with major electrical, plumbing, or structural deficiencies will be at the high end. [12]
Total estimated timeline: 3 to 8 months from assessment to Certificate of Occupancy. Bay Area jurisdictions tend toward the longer end (120–180 days processing); Central Valley jurisdictions tend toward the shorter end (45–75 days). [12]
Remember: AB 2533 eliminates impact fees and connection charges from this process. You pay normal permit and inspection fees, professional service fees, and construction costs only. [6] If you are building a new ADU rather than legalizing an existing one, the permitting timeline is now enforceable under SB 543 and SB 9 (2025) — see our ADU permit enforcement guide for how the 15-day completeness clock and 60-day approval deadline work.
What Happens If You Do Nothing
Leaving an ADU unpermitted affects appraisals, lending, insurance, and liability in ways that compound over time.
Your ADU is worth $0 on paper
Fannie Mae's Selling Guide (Section B4-1.3-05) requires appraisers to exclude unpermitted space from the gross living area (GLA) calculation. An unpermitted 600-square-foot ADU that rents for $2,500/month contributes nothing to the formal appraised value of your property. In some cases, an appraiser may apply a "cost to cure" deduction, estimating demolition or legalization costs, which can reduce overall property value below what it would be without the ADU at all. [14]
You cannot refinance against it
Fannie Mae's 2023 policy update allows rental income from permitted ADUs to qualify borrowers for loans. Unpermitted ADUs receive none of these benefits. Many conventional lenders will decline a loan application entirely when the appraiser notes unpermitted structures, because they represent a code compliance risk. FHA lenders are typically even stricter, potentially requiring the unpermitted work to be corrected before closing. [14][15]
Insurance may not cover it
If a fire starts in an unpermitted ADU, your insurer may deny the claim. If the unpermitted construction caused or contributed to the loss (faulty wiring, improper venting), the denial is near-certain under policy exclusions for code violations. Even if the insurer covers the main house, the ADU itself and liability claims from tenants may be excluded. [16]
Selling becomes complicated
California law requires sellers to disclose known material facts about a property (Civil Code Section 1102–1102.17). An unpermitted ADU is unquestionably material. Buyers' lenders may refuse to finance the purchase. Cash buyers may demand a 10–25% discount. The transaction can fall through entirely. [17]
Fines and enforcement
While AB 2533 protects homeowners who come forward to legalize, those who do not are still subject to code enforcement. Penalties for unresolved building code violations can reach $1,000 or more per day, and unpaid fines become liens on the property. In cases where violations are severe and unresolved, cities can order demolition — at the homeowner's expense. [13][16]
Tenant liability
If a tenant is injured in an unpermitted unit, the homeowner faces personal liability that insurance may not cover. Tenants can sue for violations of the implied warranty of habitability (Civil Code Section 1941). In some jurisdictions, tenants in units forced to close can claim relocation assistance of up to $25,000. [18]
The Financial Case for Legalizing
| Factor | Unpermitted ADU | After Legalization |
|---|---|---|
| Appraised value contribution | $0 (excluded from GLA) | Full market value ($150K–$400K+ in CA) [14] |
| Fannie Mae rental income qualification | Not eligible | Eligible since March 2023 [15] |
| Insurance | Claim denial risk | Standard coverage |
| Buyer pool at sale | Cash buyers only (discounted) | All buyers eligible |
| Rental income | Legally unprotectable | Fully legal, enforceable lease |
| Property tax | If discovered: back taxes + penalties | Predictable supplemental assessment |
Proposition 13 protects you from a massive tax increase
Many homeowners fear that legalizing will trigger a full property reassessment. It does not. Under California Revenue and Taxation Code Sections 70–74, legalizing an ADU is classified as "new construction," but only the ADU portion is reassessed. Your main home stays at its Proposition 13 base value.
Example: If your home is assessed at $400,000 (Prop 13 base) but has a market value of $1.2 million, and you legalize an ADU assessed at $200,000, your new total assessed value is $600,000. The annual property tax increase is approximately $2,200–$2,500. Your main home does not get reassessed to $1.2 million. [19]
Local Amnesty Programs
AB 2533 is the statewide baseline, but several cities have launched their own programs with additional support.
| City | Program Period | Key Features | Source |
|---|---|---|---|
| Berkeley | Jan 2025 – Dec 2028 | Free confidential consultation; no enforcement action during application process | berkeleyca.gov [3] |
| San Jose | Original: 2020–2022 (expired); now AB 2533 | Fee reductions averaging $5,862 per application; 5-year delayed enforcement option | sanjoseca.gov [20] |
| Los Angeles | UDU Ordinance (2017) + AB 2533 | Dedicated LADBS ADU unit; $1,000–$3,000 base cost + repairs | planning.lacity.gov [21] |
| Orange County | AB 2533 program active | 4-step process with optional pre-application inspection | ocpublicworks.com [22] |
| Hayward | AB 2533 program active | Requires owner-occupancy and deed restriction for JADUs | hayward-ca.gov [11] |
| El Cerrito | AB 2533 program active | Full HSC 17920.3 compliance required | elcerrito.gov [23] |
If your city is not listed, contact your local building department. AB 2533 is state law — every jurisdiction must comply, whether or not they have published a formal program page. Non-compliant local ordinances are void as of January 1, 2025, and HCD's Housing Accountability Unit has full enforcement authority to intervene. [24]
Decision Framework
Your next step depends on when the unit was built and what you plan to do with the property.
If your ADU was built before January 1, 2020 and you plan to keep the property: Start with a confidential third-party inspection. This costs $500–$1,500 and tells you exactly what repairs are needed without any enforcement risk. If the unit is in reasonable condition, the total legalization cost will likely be at the low end of the $16K–$62K range, and the value gained will far exceed the cost.
If your ADU was built before January 1, 2020 and you plan to sell: Legalize before listing. An unpermitted ADU narrows your buyer pool to cash buyers and reduces your sale price. A permitted ADU expands financing options for buyers and adds its full appraised value to the property. The legalization investment typically pays for itself several times over at closing.
If your ADU was built between January 1, 2018 and December 31, 2019: You are in the window that AB 2533 newly opened. The previous amnesty law did not cover you. Act now — there is no guarantee the eligibility window will be extended again.
If your ADU was built on or after January 1, 2020: AB 2533 does not apply to you. You will need to go through the standard permitting process, which means meeting current building codes and potentially paying impact fees. Consult your local building department or a licensed architect.
If you are buying a property with a known unpermitted ADU: Factor legalization costs ($16K–$62K) into your offer price. Verify the construction date to confirm AB 2533 eligibility. Get a professional inspection contingency. If the unit was built after January 1, 2020, the legalization path is more expensive and complex.
References
[1] Jo, N., Vallebueno, A., Ouyang, D., & Ho, D.E. (2024). "Not (Officially) in My Backyard: Characterizing Informal Accessory Dwelling Units and Informing Housing Policy With Remote Sensing." Journal of the American Planning Association. DOI: 10.1080/01944363.2024.2345730. Link
[2] Local Housing Solutions — Housing Solutions Lab. "California Legalized ADUs, But Unpermitted Ones Are Still Far More Common, New Research Finds." Link
[3] City of Berkeley — Amnesty Program for Unpermitted ADUs. Link
[4] Casita Coalition — "Bringing California's Hidden Housing Out of the Shadows: ADU Amnesty Reform." Link
[5] Wegmann, J. & Mawhorter, S. (2017). "Measuring Informal Housing Production in California Cities." Journal of the American Planning Association, Vol 83, No 2. Link
[6] AB 2533 Bill Text — California Legislature. Link
[7] BBK Law — "Governor Newsom Signs Three New Accessory Dwelling Unit Bills." Link
[8] BWS Law — "California's New ADU Legislation: Expanding Amnesty and Increasing Housing Potential on Multifamily Properties." Link
[9] Town of Colma — AB 2533 Program Page. Link
[10] California Health and Safety Code Section 17920.3. Link
[11] City of Hayward — AB 2533 Amnesty Program. Link
[12] AB2533.com — "Complete Guide to AB 2533 ADU Legalization in California." Link
[13] GreatBuildz — "AB 2533: How to Legalize Your Unpermitted ADU in California." Link
[14] Fannie Mae Selling Guide, Section B4-1.3-05 — "Improvements Section of the Appraisal Report." Link
[15] Fannie Mae SEL-2023-02 — ADU Policy Update (March 2023). Link
[16] LADU — "What AB 2533 Means for Unpermitted ADUs in LA." Link
[17] California Civil Code Section 1102 et seq. — Transfer Disclosure Statement Requirements. Link
[18] SKS Construction — "3 Major Legal Risks of Renting an Unpermitted ADU in California." Link
[19] California Revenue and Taxation Code Sections 70–74. Link
[20] City of San Jose — ADU Amnesty Program. Link
[21] City of Los Angeles Department of City Planning — Unpermitted Dwelling Units. Link
[22] Orange County Development Services — AB 2533 Safe ADU/JADU Legalization. Link
[23] City of El Cerrito — ADU Amnesty Program (Assembly Bill 2533). Link
[24] California HCD — Accountability and Enforcement. Link
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