A project of the Solano County Planning Collaborative

Phase Six


  • Get bids and hire a contractor
  • Understand you and your contractor’s roles during construction


The Construction phase typically takes 6-12 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 construction.

Step by Step

Building Your ADU

Keep in mind Often, people who are their own general contractors have a difficult time. Building an ADU is more like building an entire home than a renovation. If you’re working with a design/build team or have hired a general contractor, they’ll manage the project (including contract negotiation, payment schedules, quality checks, and working with local departments and staff and other agencies). While it may cost more up front, you might save a lot of money by reducing delays or change orders, and get your ADU rented sooner too.


Step 1

Hire a contractor

If you are not using a design/build firm, you will need to hire a contractor for the construction phase of your ADU.

Finding a contractor
Ask your designer and community for recommendations of good local professionals and make a list of candidates. It’s great if they have ADU experience, but it’s not necessary.

Solicit bids
You will use drawings from your designer to get bids from contractors and make sure you are specific about what you want each bid to include (license details, insurance information, examples of past work, etc.). Your design team may be able to help you with this.

Be specific about what is and is not included in the bid. Also ask for license, insurance information, references, work examples, and a proposed schedule. You’ll want at least three bids for comparison. Make sure you understand all the details of the bids and ask all necessary clarifying questions. Your designer may be able to help you compare bids and select your contractor. It’s a good idea to reach out to references and to consider your personal interactions with the contractor – you’ll want to feel like you work well together and that they understand your goals.

Beware of unrealistically low bids! Before you hire your contractor, make sure to check their license and insurance. You can verify their license by calling the Contractors’ State License Board at 800-321-2752 or checking their website. You can verify insurance by requesting a certification of insurance or by calling their insurance agent. Make sure workers’ compensation, property damage, and liability are included.


Step 2

Monitor Construction

Once you have building permits, the contractor you hire will lead the construction of your ADU. Be sure you have all funding in place before you start construction. Once your contract is signed, your contractor will start work according to the schedule you agreed upon.

Your contractor will lead the construction process and you will have the following responsibilities:

  • Communicate: Keep in touch with your contractor and schedule regular check-ins.
  • Monitor: Regularly walk through the construction area to monitor the quality of the work and make sure the work is progressing the way you expect.
  • Decide: Be prepared to make decisions about the details—light fixtures, appliances, and other materials—in a timely manner so your contractor can stay on schedule.
  • Adjust: Follow the contract you agreed to, including any changes as described specifically in a change order form. Any changes to the original agreement should be reflected in a change order form that is signed by both you and the contractor and that describes the specific change and any corresponding adjustment to the price or timeline. Beware that some changes (size, height) require official review.

Communicate frequently with your contractor to make decisions as needed and to verify progress before making payments. Timelines for construction vary, but 6-12 months is fairly common.

Key Resources


Step 3

Get inspections

During construction, your ADU will be inspected multiple times to ensure it is being built according to the permitted plans (typical inspections include foundations/footings, framing, electrical/plumbing, and exterior finishes).

Although your contractor will usually arrange the required City/County or utility inspections, it is your responsibility as the property owner to make sure that the inspections are conducted as required at each stage of the construction process.

Key Resources

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