01 / Understand the property and the purpose.
Start with the reason for the ADU. A home for a parent, a long-term rental, and flexible family space can call for different storage, privacy, access, and layout choices. Record your preferred project type, approximate size, target timing, and the priorities you will protect when tradeoffs arise.
Next, collect the existing information: property address, photos, available surveys, prior plans, and any permit history. Identify whether the proposal creates a new building, changes an existing garage, or attaches living space to the main home. Our ADU project brief helps put these questions in one place.
02 / Turn the idea into a scope you can compare.
A useful scope describes more than the building shell. It connects the plan version to site preparation, utility work, finishes, equipment, restoration, and the responsibilities outside the construction price. Open questions should be written down with a next action.
For a conversion, investigation may change what can be reused. For a detached ADU, site logistics and service routes may change the cost of reaching the building. Use our ADU budget guide to separate allowances from work that is actually defined.
03 / Coordinate design and approval.
Agree on who provides drawings and engineering, coordinates consultants, submits through the City process, responds to review comments, and updates the estimate when the design changes. Drawings, permit comments, and construction scope need to refer to the same proposed project.
A permit submission is not a promise of approval or a fixed start date. Record the decisions that depend on City review or a utility provider, then track them through the project. Visit our Costa Mesa permit guide for official starting points.
04 / Prepare for a working construction site.
Before work starts, discuss the construction entrance, delivery space, storage, temporary protection, waste removal, and the separation between the occupied home and work area. If you will remain at home, identify any service interruptions and the communication needed before them.
Confirm the inspection sequence, trade coordination, and how the schedule will be updated. When a change is needed, document the revised scope, cost, and schedule effect. A decision made clearly is easier to build correctly.
05 / Finish with a complete handoff.
Agree on the completion criteria before the final week. The handoff should address applicable inspection signoffs, remaining items, equipment information, warranty documents, and the operation of the new space. Confirm which occupancy-related approvals apply before anyone moves in.
The final walkthrough is a working review, not just a photo opportunity. Test doors, fixtures, controls, and the details included in the agreement; record anything outstanding with an owner and a next step.