Step 6

Step 6: Construction and Inspections

Your ADU is now ready for construction. During this phase, it is important to find a suitable contractor, maintain a construction timeline, and remain adaptable to unforeseen circumstances that may arise during the construction process.

Action Items:

  • Begin construction of ADU
  • Schedule inspections as required
  • Receive approvals of all inspections for occupancy

Constructing Your Adu


Contractors oversee the construction process and are in charge of getting your project built. Click below for a list of licensed contractors in California.

Construction and Inspection Timeline

While each ADU construction project is unique, generally construction for your conventional, wood frame-built ADUs can expect to follow the timeline below. Pre-manufactured or modular ADUs have a separate review and inspection process. 

Construction Step
1. Site Preparation (grading and drainage, underground utilities) Inspection Required
2. Foundation (raised foundation or slab-on-grade) Inspection Required
3. Wall & Roof Framing (Sheer) Inspection Required
4. Framing Inspection Initial Check for Plumbing, Mechanical, and Electric
5. Insulation Inspection Required
6. Miscellaneous Inspections, Where Applicable Inspections such as Stucco Lath, Gypsum (sheet rock/dry-wall), Gas Test (if applicable)
7. Final Inspections Building (structural), Plumbing, Mechanical, and Electrical
8. Occupancy After Approval of All Final Inspections


Estimated construction timelines should be discussed with your contractor/builder.


Why are they important?

Inspections are important to ensure that the building is being constructed correctly at various stages of the construction process.

Inspections provide confidence to the homeowner knowing the unseen components of the home, such as piping, electrical wires, insulation, and waterproofing have been inspected and approved. 

How many are needed?

A series of inspections must be approved before you can occupy your ADU. For a complete checklist of inspections required for your ADU see forms CDD-0339 and CDD-0401. For slab on grade designs, use form 0401 and for raised foundations, use 0339.

Contact Information

Please visit our Building Permit Inspections webpage for information on how to schedule an inspection or email

Construction Considerations

Unforeseen Circumstances that Might Impact Timeline

Building material and labor shortages can add costs and delays to your construction timeline. You should plan for unavoidable changes to your timeline.

Step 7: Move in and Operate Your ADU

You're ready for the final step! Learn about financial considerations for operating your ADU, utility costs, and resources for landlords and tenants.