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.

Unincorporated El Dorado County: Permits expire two years from date of issue. May be renewed up to twice for another year before/within 30 days of expiration, if permit holder has tried to pursue construction and has completed inspections as needed. The permit holder can apply for permit reactivation after the four-year period if the project hasn’t gotten a final inspection.

Placerville: Permit expires one year from date issued or 180 days from last approved inspection. If construction has begun, an extension may be granted by the Building Official. If no work has commenced, a new permit is required.

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.

JumpstartADU has an ADU Contractor List to help you identify professionals who work on ADU in our area. This list includes building professionals who participated in outreach events and/or requested to be included. It is not vetted and serves as an informational resource only. Be sure to do your research and reference the rest of this section before hiring anyone to work on your ADU.

See more details about the hiring process in the Hire Your Contractor step, below.

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.)

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