ADU or addition: what to check before you hire

What a complete quote should cover

Check that every quote you get prices each of these — or says clearly that it's excluded.

• Architectural plans and structural engineering — included or separate
• Soils report and site survey, if the city requires them
• Site work — grading, drainage, and access for equipment
• Foundation
• Framing, roofing, windows, and doors
• Plumbing, electrical, and heating/cooling — including connections to the main house or street
• Sewer and water connections, and a separate meter if needed
• Insulation, drywall, and interior finishes
• Permits, plan-check fees, and city impact or school fees
• Final landscaping, fencing, and walkways

Questions to ask every contractor

1. Does your price include plans, engineering, and the permit process, or only construction?
2. Have you checked whether the sewer, water, and electrical service can handle the new unit?
3. Which city fees are included, and which will I pay directly?
4. Is this a fixed price, or an estimate that can change?
5. Which items are allowances, and what dollar amount is each one?
6. What's the payment schedule, and what work is finished at each payment?
7. Who pulls the permits, and are permit fees included?
8. Who runs the job day to day, and which work goes to subcontractors?
9. How are change orders priced and approved?
10. What's the start date, how long will it take, and what happens if it runs late?
11. What warranty do you give on your workmanship?

Before you sign, check the contractor's license, bond, and workers' comp on the CSLB website. In California, a down payment should never be more than 10% of the contract price or $1,000, whichever is less.

Copy an email that asks every contractor for these answers →

The usual order of work

Every job is different, but a schedule that skips or reorders these steps is worth asking about.

1. Feasibility — zoning, setbacks, and utility capacity
2. Design and engineering
3. Plan check and permits (often the longest wait)
4. Site work and foundation
5. Framing and roofing
6. Rough plumbing, electrical, and heating/cooling, then inspections
7. Insulation and drywall
8. Finishes — flooring, cabinets, fixtures, and paint
9. Utility connections, final inspection, and sign-off from the city

Often left out of adu or addition quotes

If one quote is much lower than the others, start here.

• Sewer, water, and electrical connections (and a new meter)
• City impact and school fees
• Site work, grading, and a soils report
• Architectural and engineering drawings
• Landscaping, fencing, and walkways at the end

What does it cost?

It depends heavily on your house, your finishes, and your city, so we don't publish averages. Instead, we compare your actual quote against real project records and tell you which prices look high, which look low, and what's missing.