Buying a Home With an ADU in the Tri-Valley: What to Check First
A home with an accessory dwelling unit (ADU) can offer valuable flexibility. Whether you are considering a property in Danville, San Ramon, Dublin, Pleasanton, or Livermore, a secondary living space may provide room for extended family, a private workspace, or other future needs.
But before making an offer, look beyond the extra square footage. Is the unit properly permitted? Do the available records match what you see? Are the electrical, plumbing, heating, and other systems in suitable condition?
These questions matter because a secondary unit can affect your purchase decision, financing, insurance, renovation plans, and the property's overall value. Here is what to investigate before committing to a home with an ADU in the Tri-Valley.
Quick Answer: What Should You Check Before Buying a Home With an ADU?
Before buying a property with an ADU, verify its permit history, approved plans, final inspection status, physical condition, utility arrangements, and any applicable restrictions. Do not assume that a finished garage, backyard cottage, or converted room is an approved dwelling simply because it looks complete.
California's Department of Housing and Community Development (HCD) provides an updated Accessory Dwelling Unit Handbook, revised in March 2026, explaining state ADU requirements. Local records and the property's specific circumstances still need to be reviewed.
1. Confirm Whether the ADU Is Permitted
The first question is whether the secondary unit has the required approvals. An attractive kitchen, bathroom, and separate entrance do not establish that a space is legally approved for residential occupancy.
An ADU is generally a secondary dwelling on the same property as a primary residence. It may be detached, attached, or created by converting existing space, such as a garage.
Request the permit history and approved plans
Ask for available records covering:
Planning and building permits for the unit.
Approved construction plans and floor plans.
Inspection history and final approval documentation.
Permits for electrical, plumbing, mechanical, or structural work, where applicable.
Records of additions or alterations made after the original construction.
Compare these documents with the actual property. If the approved plans show a smaller unit, a different layout, or no kitchen, ask the appropriate local department to clarify the discrepancy.
How to check records in Danville
The Town of Danville provides an online permit history search where you can look up a property's permit history by address. Its Permit Center also provides ADU submittal requirements and related resources.
For properties in San Ramon, Dublin, Pleasanton, or Livermore, contact the relevant city's building or planning department to determine how to access the records.
Important: An absence of readily available online records does not, by itself, establish that a unit is illegal. Ask the jurisdiction how to obtain or interpret the applicable records before drawing a conclusion.
2. Understand the Difference Between a Permitted and an Unpermitted ADU
A permitted ADU has the applicable approvals documented by the responsible jurisdiction. An unpermitted or incompletely approved unit may present additional questions about safety, legal occupancy, potential corrections, and future modifications.
California law includes provisions addressing certain older unpermitted ADUs, but those provisions do not automatically legalize every existing structure.
HCD's March 2026 ADU Handbook explains current state requirements, including provisions for certain unpermitted units built before January 1, 2020.
If the property has an unpermitted or uncertain unit, ask the local jurisdiction what applies to that specific structure. Depending on the circumstances, you may need additional inspections, plans, permits, or corrective work.
Before making an offer, consider whether you would still want the property if the unit could not be used as you originally intended.
3. Inspect the ADU Separately From the Main House
A general home inspection of the primary residence may not answer every question about the secondary unit. Ask your inspector which areas are covered and whether separate inspections or qualified specialists are appropriate.
Pay attention to:
Foundation and structure: Look for visible cracking, water intrusion, settlement concerns, or other signs that warrant further evaluation.
Roof and exterior: Review roof condition, drainage, siding, windows, and weatherproofing.
Electrical: Check the visible condition of the electrical system and whether the installation raises questions requiring a qualified electrician.
Plumbing: Evaluate visible plumbing, drainage, fixtures, and signs of leaks.
Heating and ventilation: Determine how the unit is heated and ventilated and whether the equipment is appropriate for the space.
Moisture and ventilation: Look for musty odors, staining, condensation, and signs of inadequate ventilation.
Fire and life safety: Ask the inspector or appropriate building official to identify concerns relating to alarms, exits, and other applicable safety requirements.
The California Department of Real Estate's Information for Homebuyers recommends evaluating property condition, reviewing disclosures, and using appropriate professional guidance during a purchase.
An inspection does not guarantee that every defect will be identified or establish that the unit complies with every legal requirement. Use the findings to determine whether additional specialist inspections or municipal review are necessary.
4. Investigate Utilities, Access, and Ongoing Costs
Two ADUs with similar layouts can have different practical arrangements for utilities, maintenance, and access. Before purchasing, understand how the secondary unit operates and what expenses may come with it.
Questions worth asking
Does the ADU have separate utility meters, or does it share services with the main house?
How are electricity, water, sewer, and heating provided?
Is the existing electrical capacity adequate for the equipment installed?
Are there shared access paths, parking arrangements, or maintenance responsibilities?
Are there drainage or grading issues that affect the backyard structure?
Does the property have additional insurance considerations?
Are there HOA restrictions or other recorded obligations that require review?
Do not assume that a separate entrance means separate utility billing or that a detached structure has independent services.
The answers can help you estimate the property's ongoing costs and determine whether any upgrades may be necessary.
5. Evaluate the ADU's Effect on Value and Financing
An ADU may make a property more appealing to some buyers, but the additional structure does not automatically translate into a predictable increase in market value.
The unit's condition, permitted status, size, functionality, utility arrangements, and comparable sales can all influence how buyers and appraisers evaluate the property.
For example, imagine two homes in Danville with similar primary residences. One has a documented, well-maintained detached ADU. The other has a converted garage with an uncertain permit history.
A buyer may view the two properties differently because the secondary spaces present different levels of certainty, usability, and potential expense. This is an illustrative comparison, not a claim about a particular property's value.
Before deciding what to offer, review comparable sales and ask your lender how the ADU and its documentation may affect the appraisal and loan underwriting.
If you plan to use projected income from the unit to support your purchase, ask the lender what documentation and eligibility requirements apply. Do not assume that potential income will automatically count toward qualifying for a mortgage.
6. Review Disclosures, Property Records, and Restrictions
A property with an ADU deserves the same careful review as any other home, with additional attention to the secondary structure.
Request the available seller disclosures, permits, plans, inspection reports, warranties, and records of repairs or alterations. If the property is part of an HOA, review the governing documents and relevant restrictions with appropriate professional guidance.
You should also determine whether the ADU's actual configuration matches the information being provided about the property.
If the unit's status is unclear, consider asking the seller for additional records or seeking clarification from the local building department before your contractual deadlines expire.
Do not rely exclusively on listing descriptions, marketing materials, or verbal assurances when a material question can be investigated through official records or qualified professionals.
7. Your Pre-Offer ADU Checklist
Before committing to a home with an ADU in the Tri-Valley, work through this checklist:
Obtain the available permit history and approved plans.
Confirm final inspection or approval status with the relevant jurisdiction.
Compare the records with the existing layout and features.
Arrange an appropriate inspection of the secondary unit.
Investigate electrical, plumbing, heating, drainage, and structural concerns.
Understand utility connections, access, parking, and maintenance.
Review seller disclosures, HOA documents, and applicable restrictions.
Ask your lender about appraisal, financing, and any proposed income assumptions.
Estimate potential repair or correction costs before finalizing your budget.
Review your purchase contract and contingency deadlines with your real estate professional.
Not every property will require every step, and the appropriate level of investigation depends on the unit's age, construction, documentation, and condition.
Agent's Insight: Waleed "Walter" Akbar's Local Perspective
When evaluating a home with an ADU, I encourage buyers to separate the property's potential from what has actually been documented.
A secondary unit may be a meaningful benefit, but buyers should understand its condition, approvals, operating costs, and limitations before deciding how much it is worth to them.
In the Tri-Valley, I recommend making the ADU part of the initial due-diligence conversation rather than treating it as a bonus feature to investigate after the offer is accepted. That gives you a clearer basis for comparing properties, evaluating the asking price, and deciding which questions need answers before you move forward.
Frequently Asked Questions
Does an ADU need a permit in California?
ADUs generally require applicable local approvals. The specific requirements depend on the project, the existing structure, and the laws and regulations that apply. Consult the relevant local jurisdiction and review HCD's current ADU guidance.
Can I buy a home with an unpermitted ADU?
You may be able to purchase a property with an unpermitted secondary structure, but you should understand the implications before proceeding. The structure may require additional review, corrective work, or permits, and its use may be limited. Ask the local jurisdiction to evaluate the specific circumstances.
Does a permitted ADU automatically increase a home's value?
No. Value depends on the property, the unit's condition and functionality, relevant comparable sales, market conditions, and other factors. A permitted ADU can provide additional flexibility, but no universal premium should be assumed.
Can I use ADU income to qualify for a mortgage?
Potentially, depending on the loan program, lender requirements, documentation, and the property's circumstances. Ask your lender how any proposed income will be evaluated before relying on it in your purchase budget.
Where can I check ADU permits in Danville?
Start with the Town of Danville's online permit history search and its Permit Center. For properties elsewhere in the Tri-Valley, contact the applicable city or county building department.
Looking for a Home in the Tri-Valley?
Whether you are buying your first home, moving up, or looking for a property with a flexible secondary living space, a careful review of the home's records and condition can help you make a more informed decision.
For personalized guidance buying or selling a home in San Ramon, Danville, Dublin, Walnut Creek, Alamo, Pleasanton, or Livermore, contact Waleed "Walter" Akbar at Everhome Real Estate at (510) 541-1610.
Visit WalterAkbar.com to learn more about working with Walter.
This article is for general informational purposes and is not legal, tax, construction, lending, or permitting advice. Requirements and outcomes vary by property and jurisdiction. Consult the appropriate qualified professionals about your specific circumstances.