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ADU construction checklist, stage by stage

By the HyreADU research desk. Last checked .

The short answer

An ADU construction checklist follows the build in order: before work starts, foundation, framing, rough-in of plumbing, electrical and mechanical, insulation, drywall, finishes and final.

At each stage, confirm the city inspection passed before the next one covers it, and pay only for work that is done. Keep every signed inspection and change order on file.

Before work starts

  1. Permit issued and posted on site.
  2. Contract signed, with a down payment within the California cap of $1,000 or 10 percent, whichever is less (Bus. & Prof. Code § 7159.5).
  3. Contractor’s license, bond and workers’ compensation checked on the CSLB site.
  4. Utility locate called before digging.

During the build

  1. Foundation: forms and steel inspected before concrete is poured.
  2. Underground plumbing and the sewer connection inspected before backfill.
  3. Framing inspected, with structural hardware as drawn.
  4. Rough plumbing, electrical and mechanical inspected before insulation.
  5. Insulation inspected before drywall.
  6. Drywall nailing inspected where your city requires it.
  7. Finishes, fixtures and final inspection.

Paperwork to keep

  • Every change order, signed before the work it covers (Bus. & Prof. Code § 7159).
  • Preliminary notices from subcontractors and suppliers; in California these warn of possible lien rights (Civ. Code § 8200).
  • Payment records tied to each finished stage.
  • Photos of walls before they are closed, for future repairs.

A mistake to avoid

The mistake to avoid is paying ahead of the work. California bars a contractor from asking for or accepting payment that exceeds the value of the work done or materials delivered (Bus. & Prof. Code § 7159.5). Compare each invoice with what is on site.

What to do next: check your lot with the ADU feasibility checker, read the questions to ask an ADU builder, then tell us about your project. Matching is not live yet, so we reply with information, not a quote.

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Questions

How many inspections does an ADU need?

Several, at each stage above. Your permit card lists them.

What is a preliminary notice?

In California, a notice a subcontractor or supplier sends to preserve possible lien rights. Keep it and ask for lien releases when you pay.

Should I be on site?

Visit at each stage and before walls close. Take photos.

What if the schedule slips?

Ask for a written update. The contract should state approximate start and completion dates.

Sources

HyreADU is a publisher. It does not design, permit or build ADUs, has no partner builders, and gives no legal, tax, lending or engineering advice.

Rules vary by state and city; California rules are labeled as such. Spotted an error? Tell us through our corrections page. Licensed professionals can also contribute as named sources.