An ADU (accessory dwelling unit) is an independent second home on the same lot as the main house, and in the Bay Area it changes both sides of a transaction. A buyer needs to verify that the unit is actually permitted, because permit status drives value, lending, and insurance. A seller needs to know what the unit will honestly appraise for, and, in a small but growing list of cities, whether AB 1033 lets it be sold separately as a condominium.
This guide walks through how to verify an ADU's permit status step by step, what an unpermitted unit does to a deal, where AB 1033 stands in the Bay Area as of mid-2026, and how appraisers treat an ADU at sale. It is general education, not legal advice, and permit practice varies city by city.
What counts as an ADU, and what is a JADU?
An ADU is a complete, independent dwelling on the same lot as a primary home: its own kitchen, its own bathroom, its own entrance. It can be detached (a backyard cottage), attached to the house, or converted from existing space such as a garage or basement. California's Department of Housing and Community Development publishes the definitive state-level rules and an updated handbook on its ADU page, and state law has spent the last decade forcing cities to approve them more readily.
A JADU (junior accessory dwelling unit) is the smaller cousin: capped at 500 square feet, created within the walls of the existing home, allowed an efficiency kitchen, and permitted to share a bathroom with the main house. JADUs typically come with an owner-occupancy requirement on the property, which matters if you are buying for rental income. When a listing says "in-law unit," your first question is which of these, if either, the city record actually shows.
How do you verify an ADU is actually permitted?
The MLS description is a claim, not a record. "Permitted ADU," "legal second unit," and "buyer to verify" all appear in Bay Area listings above units the city has never inspected. Verification runs in a chain, and each link is checkable during your inspection period:
Start with the permit history. Most Bay Area cities expose building-permit records through an online portal, and the building department can print a history for the address. You are looking for a permit that was not just issued but finaled, meaning the work passed its inspections. An application that was opened and abandoned, or a permit issued with no final inspection, does not make the unit legal.
Cross-check the county assessor. Assessor records show what square footage and how many units are on the tax roll. A two-unit reality sitting on a one-unit record is a flag. The reverse is not proof either: assessor data is for taxation, not permits, so treat it as a cross-reference rather than an answer.
Ask the city building department. When the portal is ambiguous, a records request or a counter conversation settles what the city has on file, including any open code-enforcement case. Procedures and turnaround vary by city, so start early. And walk the unit with your inspector: unpermitted conversions tend to show their shortcuts in wiring, egress, and ceiling heights, which is exactly the territory of my guide to home inspection red flags.
Permitted, unpermitted, legalizable: three different assets
Once you know the permit status, you know which of three very different assets you are dealing with. The label on the listing may be identical; the economics are not:
| Permitted ADU | Unpermitted ADU | Legalizable under AB 2533 (pre-2020) | |
|---|---|---|---|
| Value at appraisal | Counted as living space; often still credited below construction cost | Often largely discounted; may be valued as storage or not at all | Discounted today; potential upside after legalization |
| Lending | Rental income may help qualification on some programs; lender rules vary | Some lenders question or condition the loan; income rarely counted | Treated as unpermitted until the city signs off |
| Insurance | Insurable as a dwelling unit | Claims tied to unpermitted space can be contested; disclose to the insurer | Same as unpermitted until legalized |
| Disclosure at sale | Straightforward; permits document the story | Must be disclosed as unpermitted; never marketed as legal | Disclose status and any legalization work in progress |
The table is directional, not a promise: appraisal outcomes vary, lender and insurer rules differ by program, and every city runs code enforcement its own way. Confirm the specifics with the city building department and your agent.
What an unpermitted ADU does to value, lending, and insurance
An unpermitted unit is not a smaller version of a permitted one; it is a different thing wearing the same clothes. Appraisers may decline to credit the space as living area, lenders can condition or rethink a loan when the property does not match the record, insurers can contest claims that arise in space they were never told about, and the city can open a code-enforcement case that lands on whoever owns the property when it starts. None of that makes the house unbuyable. It makes the unit worth what an unpermitted unit is worth, and the negotiation should reflect that.
I keep the full playbook, including red tags, cost ranges from cases I have handled, and the negotiation math, in the dedicated guide to buying a Bay Area home with unpermitted work. If the listing you are weighing has an unpermitted unit, read that one next; this section is the summary, not the substitute.
One statewide law softens the picture for older units. California's AB 2533, in effect since 2025, gives unpermitted ADUs and JADUs built before January 1, 2020 a friendlier legalization path: cities must focus on health-and-safety corrections rather than a full code rebuild, and they cannot deny legalization over code or zoning violations alone unless the unit is a genuine hazard. The unpermitted-work guide covers how that works in practice; the short version is that a pre-2020 unit may be fixable at a cost worth negotiating over, and each city applies the law its own way.
AB 1033: selling an ADU separately as a condo
Historically an ADU could not be sold apart from the main house; one lot, one sale. AB 1033, effective 2024, changed the ceiling but not the floor: it lets a city or county pass a local ordinance allowing ADUs to be sold separately as condominiums. The key word is lets. AB 1033 is opt-in, and in a city that has not adopted an ordinance, nothing changes.
As of mid-2026 the Bay Area list is short. San Jose opted in first, in 2024, and the first ADU condominium sales in the state closed there in 2025. San Francisco adopted its own ordinance in July 2025, deliberately limited to newer units so existing tenants are not displaced. Berkeley and a few other cities have studied the idea without adopting it, and most Bay Area cities have not opted in at all. The list moves, so before you build plans on it, confirm the current ordinance status with the city planning department.
Even where it exists, the path is not a paperwork formality. Converting an ADU into a sellable condominium means recording a condominium plan, setting up shared arrangements for the lot the two homes still share, and obtaining consent from every lienholder on the property, so a homeowner with a mortgage needs the lender to agree. If you are buying a home hoping to sell the ADU later, or buying an ADU condo itself, treat it as a small subdivision project and price the professional help accordingly.
What an ADU adds when you sell
A permitted ADU is a genuine selling point in the Bay Area: it widens the buyer pool to multigenerational families, buyers who want space for parents or a tenant, and investors reading it as income. Documented rent strengthens the story, and if income is part of your pitch, the arithmetic buyers will apply is the same one I lay out in the guide to East Bay rental-property yields.
Then comes the appraisal, and this is where sellers most often feel shortchanged. Appraisers work from comparable sales, and homes with ADUs are still thin on the ground in many neighborhoods, so the unit is frequently credited well below what it cost to build. A pretty short-term-rental listing does not move a comp grid; closed sales do. In ADU cases I have walked through in my webinars, the gap between what an owner expected the unit to add and what the appraiser credited was often the single biggest surprise in the deal. Appraisal outcomes vary by neighborhood, appraiser, and loan program, so set your list price with your agent on real comps, not on construction receipts.
If your ADU has any permit ambiguity, resolve it before listing, not during escrow. Pull your own permit history, consider the legalization route where it applies, and disclose whatever remains plainly. Buyers forgive a disclosed history far more readily than a discovered one.
The bottom line
An ADU is either a documented second home or an undocumented one, and everything else follows from that fact. Buyers: verify the permit chain (listing claim, permit history, assessor record, building department) before the contingency clock runs out, and price the unit as what the record says it is. Sellers: know what your unit will actually appraise for, fix or disclose its permit status early, and treat AB 1033 as a city-by-city possibility rather than a given. The homework is boring and the stakes are not.
Let's verify it together
If you are weighing a listing with an ADU, send it to me and I will help you run the permit chain before you offer: what the city portal shows, what the assessor shows, and what questions to put to the building department. If you own a home with an ADU and are thinking about selling, I will tell you honestly what the unit is likely to appraise for and what is worth resolving first. Across 104 documented closings and more than $115M in volume, units like these have decided more negotiations than almost any other single feature.
Reach me directly at lilyagaripova@gmail.com or (415) 910-3958, or at lilygaripova.com. I work out of Fremont, CA, and I would rather you ask the question early than discover the answer in escrow.
Lily Garipova, REALTOR®, in real estate since 2007, California licensed since 2016 (Cal DRE #02010731).
Email: lilyagaripova@gmail.com
Phone: (415) 910-3958
Web: lilygaripova.com
Fremont, CA
FAQ
What is the difference between an ADU and a JADU?
An ADU (accessory dwelling unit) is a complete independent home on the same lot as the main house, with its own kitchen, bathroom, and entrance. A JADU (junior ADU) is smaller, capped at 500 square feet, carved out of the existing house, allowed an efficiency kitchen, and it may share a bathroom with the main home. JADUs also typically require the owner to live on the property. The two follow different rules, so check which one the listing is actually describing.
How can I tell if an ADU is permitted before I write an offer?
Do not rely on the MLS description. Pull the property's permit history from the city building department (many Bay Area cities have online permit portals), and look for a finaled permit for the unit, not just an issued one. Cross-check the county assessor's records to see whether the extra unit or square footage is on the tax roll, and when anything is unclear, ask the city building department directly. Your inspection period is the time to finish this homework.
Does an unpermitted ADU mean I should not buy the house?
Not automatically. It means you should price and plan for what the unit really is: unwarranted space that an appraiser may largely discount, that some lenders and insurers will question, and that could draw code enforcement. Some buyers negotiate the price down and legalize the unit after closing; others walk away. The mistake is paying permitted-ADU money for an unpermitted one.
Can an ADU be sold separately from the main house in the Bay Area?
Only in cities that have opted into AB 1033 by local ordinance, and only through a condominium structure with its own requirements, including lienholder consent. As of mid-2026, San Jose has an active program with the first ADU condo sales closed in 2025, and San Francisco adopted its own ordinance in 2025 for a limited set of newer units. Most Bay Area cities have not opted in, so confirm the current status with the city planning department.
How much value does an ADU add at appraisal?
Usually less than the owner expects. Appraisers work from comparable sales, and homes with ADUs are still thin in many Bay Area neighborhoods, so a unit that cost a lot to build may be credited well below its construction cost. A permitted unit with documented rental income generally appraises better than an unpermitted one, but outcomes vary by neighborhood, lender, and appraiser, so confirm with your agent and lender rather than assuming dollar-for-dollar credit.
What is AB 2533, and can it legalize an older unpermitted ADU?
AB 2533 is a statewide California law, in effect since 2025, that makes it easier to legalize an unpermitted ADU or JADU built before January 1, 2020. Cities must focus on health-and-safety corrections rather than requiring a full code rebuild, and they cannot deny legalization over code or zoning violations alone unless the unit is a genuine hazard. Each city runs its program differently, so confirm the details with the local building department.
Do I have to disclose an unpermitted ADU when I sell?
Yes. California sellers must disclose known material facts, and an unpermitted unit is exactly that. Disclose it plainly in the Transfer Disclosure Statement and related forms, and never market unpermitted space as a permitted ADU or its income as established rental income. Honest disclosure protects the sale and protects you after closing.
