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If you have questions about the ADU permitting process, please reach out to our ADU
Ally at the Permit Center:

ADU Ally

Phone: 408-793-5302

Common Questions about ADUs
Please read the ADU Universal Checklist for information on the Zoning Code and permit process for an ADU. In addition to that information, here are common questions and answers for ADU projects:

  1. Can I build a new house and ADU at the same time?


  2. Can I build an ADU where the single-family house is a rental?


  3. Can I rent the house and ADU to different parties? 


  4. Can I build an ADU on a property with a duplex or apartment building?


  5. 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.

  6. 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.

  7. Is an ADU required to have separate utilities?

    Utilities can be combined with the main residence OR can be separate.

  8. Is an ADU required to have fire sprinklers?
    • If the main house has fire sprinklers, the ADU must have fire sprinklers.
    • If the project is an attached ADU greater than 500 sq. ft. AND the overall gross floor area with the main house exceeds 3,600 sq. ft., then fire sprinklers are required for the entire house and ADU.
    • Sprinklers may be required for a detached ADU that is built with less than a three-foot setback.
    • Please see the ADU Universal Checklist, Section D. for more information about fire sprinklers.For questions, call 408-535-7750 and ask to speak with a fire permit specialist.
  1. 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:

  2. 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 profeessional 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:  or 408-793-5302
  3. How much is the building permit? 

    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:
    • School fees
    • Park Impact fees
    • Fees for any clearances or other permits as may be applicable, such as a Geohazard Clearance, Tree Removal Permit, or a Fire Variance, for example.

  1. How long does it take to get my plans approved?

    Typically 20 business days unless your plan requires more than a first review. 

Our video, "Permits for ADUs" on YouTube may help you understand the planning, permit and plan review process: