If you have questions about the ADU permitting process, please reach out to our ADU
Ally at the Permit Center:
The ADU Universal Checklist or the video at the bottom of this page will answer many questions about:
- Which lots qualify for an ADU and where you can locate the ADU on your lot
- Setback, height, and fire requirements
- Getting a building permit and plan review
In addition, here are answers to some questions we frequently hear from ADU customers. If this information doesn't address your question, reach out to our ADU Ally at at ADU.Ally@sanjoseca.gov or 408-793-5302.
- What is the total cost for an ADU?
It will depend on the size and type of ADU. A new, custom-built detached unit may cost as much as $250,000. Retrofitting an existing attached garage or basement may cost approximately $80,000 to $150,000, depending on size, existing plumbing, and how you design the space.
- How might I save money on the construction cost of an ADU?
- Install a pre-fabricated unit.
- Select a plan that has been pre-approved by the City.
- Smaller units -- 500 sq. ft. or less -- will cost less to build; have lower permit fees;
- and avoid school impact fees.
- Where can I find information about the cost of a building permit and any other fees?
See the ADU Fees page. The building permit fee depends on the square footage of the ADU. City staff will provide you with a free estimate if you complete the Permit Cost Estimate Worksheet. Other fees may apply:
- Will my property taxes increase if I build an ADU?
Yes. The primary house will not be reassessed, and your base assessment of the primary house will not be affected, but your taxes will increase based on the value of the ADU. For more information, visit: www.sccassessor.org
- How can I finance my backyard unit?
Many homeowners take out a home equity loan, renovation loan, or a cash-out refinance loan.
WHERE CAN I BUILD AN ADU?
As explained on the the ADU Universal Checklist, one ADU is allowed on a lot zoned for single-family residential use, and where one single-family home is on the property.
- Can I build a new house and ADU at the same time?
- Can I build an ADU on a property with a duplex or apartment building?
No. However, currently there are state legislative proposals that may change this.
- Can I build an ADU on the side of my house or in the front yard?
An attached ADU can be built on any side of the house, but front and side setback rules will apply. See the ADU Universal Checklist for more information.
A detached ADU, at this time, can only be built in the backyard. The City is currently working on an Ordinance update that would allow a detached unit to be built outside of the rear yard as long as it is at least 45 feet from the front property line and maintains a minimum 5-foot setback from the side yard. There are also rules about the distance of the ADU to the main home. See the ADU Universal Checklist for more information, or speak with a Planner at 408-535-3555.
RENTAL PROPERTY QUESTIONS
- Can I build an ADU where the single-family house is a rental?
- Can I rent the house and ADU to different parties?
- Can I rent the ADU to whomever I choose?
A homeowner has the right to rent their ADU to anyone they choose, however, as a landlord you must comply with fair housing laws. You cannot establish discriminatory terms or conditions in the rental advertising or agreement. You cannot advertise or establish that the unit is available or not available to people of a certain race, color, religion, sex, handicap, familial status, or national origin, and you cannot refuse housing vouchers.
Learn more at the Renters & Landlords page at: www.sanjoseca.gov/housing
- Is an ADU required to have its own address?
Yes. An address will be assigned to the ADU as part of the building permit process.
- Is an ADU required to have separate utilities?
Utilities can be combined with the main residence OR can be separate.
- Can an ADU have a porch, and does the porch count in the allowed square footage for the unit?
ADUs can have a porch. If the porch is uncovered, it will not count toward the maximum floor area allowed. If the porch is covered and is 50% or more enclosed with walls, then it will count toward the allowable floor area of the ADU.
PERMIT PROCESS QUESTIONS
- How do I get a building permit for an ADU?
We highly recommend hiring a professional architect, designer, or contractor to create the building plans that are necessary to obtain a permit. This professional can submit the plans with a Building Permit Application at the Permit Center. City staff will review the plans for compliance with the building code; if approved and all fees are paid, they will issue a building permit. Contact our ADU Ally for help with the permit process: email@example.com or 408-793-5302.
- How long does it take to get my plans approved?
Typically 20 business days unless your plan requires more than a first review.
For more information, check out our video, "Permits for ADUs" on YouTube: