ADUs – also called granny flats, converted garages, or basement apartments – are flexible spaces that meet the changing needs of households over time. ADUs can be attached or detached from the primary home, up to 1,000 square feet, and must have their own entryway, kitchen and bathroom.

located within the existing footprint of a home, including an attached garage, and are no more than 500 square feet. They also need their own entryway and bathrooms, and kitchen area, which can be an efficiency kitchen.

From space for your loved ones to supporting the community and building your retirement through renting, your ADU will grow with you. To learn more about types of ADUs visit here.

 Getting Started

Interested in learning more? These resources will help you learn more about ADUs, what is possible on your property and city rules:

•  Summary of ADU and JADU Regulations find out about City of Calistoga rules
• FAQ find out answers to frequently asked questions
• Napa Sonoma ADU look at pre-reviewed or standard plans at Napa Sonoma ADU Standard Plans Program, hear from neighbors on what they built, download the free ADU Workbook or schedule a free ADU Feasibility Consultation Questions? Visit the program’s FAQs page, here, or contact us.
• ADU Glossary find out about frequently used terms
• Address Look-Up Tool find out what you are eligible to build
• ADU Calculator estimate potential costs and rents

 Building Permit and Process

Although you can build an ADU as an owner builder, we recommend hiring a licensed architect or designer to design your ADU and a licensed builder to construct it, or a design/build team for the entire process. Whoever you hire will help with the application process. Here are some important resources, links to forms and key steps to the process:

• ADU Process Graphic find out information on every step of the process from thinking about it to move in.
• ADU Checklist
• Important Forms:
  • Building Permit Application
  • Permit Process Flowchart
  • Permit Submittal Checklist
• Pre-Application Reviews are available. Call or email the Planning and Building Department to schedule.
• Permit Application Reviews are complete within 20 business days. Resubmittals will be reviewed within 10 business days.
• Collect Your Permit once your application is approved and fees are paid.
• Final Inspection will be scheduled by your builder by visiting our Portal or calling 707-942-2827. Once your ADU has passed, your ADU is ready for move-in!

Fees and Other Potential Costs

The size and valuation of your ADU will determine your building permit fees. See the Building Fee page for fee information.

You may need to be pay fees to other departments or agencies, depending on your property and its location:

• Water and Sewer Utilities: ADUs may require new or separate utility connections. Contact Public Works at 707-942-2828.
• Septic Systems: Some sites may require improvements. Contact the Napa County Environmental Health Division at 707-253-4417.
• School Fees: Required for ADUs more than 500 square feet. Contact Calistoga Joint Unified School District at 707-942-4703.
• Impact Fees: Required for ADUs more than 750 square feet or when the ADU is constructed at same time as a new SFD.

Legalize Your Existing ADU

If you constructed an ADU without getting a building permit, you may want to consider legalizing it. Doing so can reduce liability and risks to occupants, increase property value and provide peace of mind. Contact the Planning and Building Department to learn more. There is no fine or penalty for legalizing an existing ADU and no enforcement will result from contacting us.

Owner Occupancy and Short-Term Rentals

ADUs and JADUs can be rented for 30 days or more if a business license is obtained by property owners. For JADUs, the owner must live on the property, in either the main home or JADU.

Note: Calistoga does not allow Short Term Rentals