A project of the Solano County Planning Collaborative

Phase Four


  • Understand what’s required in your permit application
  • Know what to expect from application review
  • Get started on your application
  • Understand the types of fees you may need to pay


The Permitting phase typically takes 1-6 months. Most ADU projects take 12-18 months to complete, but some extend to 24 months or more.


Here are a few of the most frequently asked questions about permitting.

Questions about Special Zones

Step by Step

Permitting Your ADU

Before you begin It’s helpful to discuss your project with City or County staff before submitting your application. While not required, doing so might save time later in the process. See the Contact page for contact information and check out our ADU Worksheets for help planning the meeting.


Step 1

prepare your application package

Once your ADU plans are finalized, you and your designer or contractor will submit your application package for approval. Your team will lead the process to prepare an application package. Requirements will vary by location, but applications for typically include:

  • Site plan (depicting existing and proposed structures)
  • Building/architectural plans (floor plans, elevation plans, and details)
  • Structural plans (foundation plan, framing plans, and associated details)
  • Other items (Title 24 energy calculations, deed restriction, address assignment form, or other materials required by your location)

Talk to City or County staff for information on specific requirements.

Once your ADU plans are finalized, you and your designer or contractor will submit your application package for approval.


Step 2

Submit your application

Submitting an application is typically different in every city or county. Some have online portals, and others ask that paper copies be submitted in-person. Some fees may be due when submitting your application, and some may be due later. Check with City or County staff for more details.

After your application is submitted, the first step will be for your local staff to review it for completeness. They will confirm your application is complete (meaning you correctly submitted all required materials and details) and then other departments and agencies will begin their review.


Step 3

Revise your application

Staff will complete their review and provide any comments. Most likely, this review will happen at a staff level (no hearings), but in less common instances, an additional permit or public hearing may be required.

If modifications to your plan are required (at least one round of revisions is typical), your team will revise and resubmit the application. Under state law, agencies/departments reviewing your plans must provide a full set of comments with a list of incorrect items and how those can be fixed.


Step 4

Recieve Permits

After your application is approved, staff will let you know that your permit is ready and how you can receive it. Once you have paid any remaining fees and you have your permit, you can begin construction. Permits generally must be displayed at the site.

Permit & Application Fees

ADUs can be charged a variety of fees from the City or County, the State, and other agencies. Some fees are based on the details of the project while others are fixed. Surprisingly, local governments do not control many of the most expensive fees, like school and water fees, which are assessed by other agencies and dependent on the size or location of your ADU.

The total amount of fees depends on your property and plans. Some fees based on valuation, some flat. All together, fees for ADUs typically fall in the $10,000-15,000 range when school district and impact fees are applicable or substantially less (as low as $1,000 but could be $7,000 or more) for smaller ADUs. Impact fees cannot be charged for ADUs under 750 square feet, so that is often a size cutoff for increased fees.

The fees listed below are often required, but the exact list of fees and when they are due will vary by location:

  • Planning permit fees
  • Plan check fees
  • Building permit fees (generally due when your permit is issued)
  • Other department fees (staff will let you know what applies to your project)
  • School District fees (often only applies to ADUs over 500 SF)
  • Development impact fees (only applies to ADUs 750 square feet or more)
  • Utility and sanitation (contact utility agencies as you develop the design for your ADU for more information)

Estimating fees

The total amount of fees depends on your property and plans. Staff may be able to provide an estimate once you have a good idea of your project details.

Not sure what questions to ask?

Check out our ADU worksheets

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