A project of the Solano County Planning Collaborative

Phase Four


  • Identify what you want in a design
  • Understand the design process and professionals involved
  • Hire a professional team to create your design


The Design 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 ADU design.

Step by Step

Designing Your ADU

Before you beginIt is helpful to have a clear sense of what you want early in the process. An architect or designer can help you brainstorm, but they cannot start designing until you’ve made basic decisions like the type of ADU you want (see Getting Started) and how many bedrooms it will have. Our Worksheets can help you think about these questions.


Step 1

Hire experienced professionals

Although you can build an ADU as an owner builder, we strongly recommend hiring a licensed architect or designer and a licensed contractor, or a design/build team, and most homeowners do. Bringing on a professional early in the process is often key to getting your ADU approved quickly, managed efficiently, and built cost-effectively. Relevant experience and fit are critical, and it’s important to look at their past work and check references.

Your team may include one or more of the following:

  • Licensed architect or designer to design your ADU and potentially see you through permitting and construction
  • Licensed contractor to build your ADU
  • Design/build company that designs and builds your ADU
  • Modular/prefab company who sells preset designs for modular/prefab homes


Step 2

Create initial design

Once you have your team in place, you will work with them to design your ADU. Together you will consider size, use, layout, specific project needs (storage, laundry room, etc.), architectural style, and privacy.

First, you’ll likely get conceptual drawings – drawings based on measurements of your property (perhaps a property survey), local rules, and the type and size of ADU you want. These drawings can also be helpful in finalizing what you want.

Once conceptual drawings have been approved, you’ll get refined drawings that include structural and design components.

Once you have an initial design, it’s a good idea to discuss it with local Planning or Building staff so they can point out any issues before submitting your permit application. Your design team can join you to clarify drawings and help you understand requirements.

If you haven’t already, this is also a good time to reach out to utility service providers (water, sewer, gas, etc.) to confirm your design meets their requirements. See the Contact page for all relevant contact information.


Step 3

Finalize plan

Based on the initial discussion with City or County staff, your team will work through any required changes and prepare the permit application (see Permitting).

Many homeowners also get construction drawings from their designer that provide all the details needed for a contractor to bid on the project (see Construction). Potential contractors will likely want to visit the site along with seeing the drawings.

Organize your design ideas

Check out our ADU worksheets

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