As soon as the final inspection is complete, your ADU is ready for move-in! Make sure utility services are set up, an address is established, and other preparations are in place. See the Renting & Move-in guide for more responsibilities of being a landlord.

While your contractor will lead the construction process, you will have the following responsibilities:

• Keep in touch with your contractor and set up a schedule for checking in.
• Regularly walk through the construction area to monitor the quality of the work and make sure the work is progressing the way you expect.
• 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.
• Follow the contract you agreed to, including any changes as described specifically in a change order form.
• Although your contractor will usually arrange the required city or utility inspections, it is your responsibility as the property owner to make sure that the inspections are conducted as required.

Traditional construction will take 6-12 months, though this will vary depending on the specifics of the project. Stages of construction include:

• Site preparation: 1-2 months
• Foundation: 1 month
• Walls, roof, doors: 1-2 months
• Plumbing & electrical: 1-2 months
• Insulation & drywall: ½-1 month
• Fixtures & finishes: 1-2 months
• Final touches: ½-2 months

Construction costs for your ADU will vary significantly depending on personal preferences, site conditions, location, and many other factors.

Size: Despite what many think, smaller ADUs may cost almost the same as larger ones. Many costs like foundation, kitchen and bathroom work only increase slightly for larger ADUs. Kitchen costs will range from $25,000–$50,000 with each bathroom ranging from $15,000–$25,000.

Type: New construction, both detached and attached, tend to be the most expensive. Garage conversions are not much cheaper than new construction if at all. Conversions of interior space (basement or otherwise) are often the cheapest.

Other factors:

• Quality of interior finish work and amenities
• Architectural form and details
• Extent of utility, structural, mechanical, electrical, and plumbing upgrades required
• Required site upgrades (sidewalks, sewer and water)
• Whether sprinklers are required
• Whether doors and windows meet emergency exit standards
• Lot complexity (slope, trees, fault lines, etc.)

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

First, you’ll solicit bids. You will want to get at least three bids for comparison. When you have bids, you can begin selecting your contractor.

Before you hire a contractor, make sure to check their license and insurance and when they present you with a contract, review everything carefully.

Permits typically expire 1-2 years from date of issue but this will vary based on your location. Talk to City or County staff to find out.

In most cases, state law no longer allows cities and counties to comment on pre-existing zoning issues unrelated to the ADU. For example, you should not receive comments about correcting the main house or a fence unrelated to the ADU, unless there is an obvious public safety issue.

State law says an ADU permit cannot be denied due to nonconforming zoning, building code violations or unpermitted structures unless there is a threat to public health or safety, and they are not affected by building the ADU.

Building an ADU is an investment of time as well as money. Most projects take one to two years to complete. Typically, it takes homeowners one to three months to get started and assemble their team, then one to six months to develop plans, meet with the city, and submit the application. Depending on what permits are required, how many rounds of review are required and how quickly a homeowner and their project team can respond to comments, it will take one to six months to get permits. Construction usually takes six to twelve months.