First, check what is actually available.
The City's preapproved ADU page describes the program, while its plan directory is marked “coming soon” at our September 5, 2026 review. Do not assume a catalog design is currently available to select. Confirm current status directly with the City.
Your property still needs its own work.
A site plan is still required. A standardized building design does not establish the right placement, access, service routes, or construction logistics for your parcel. Discuss the submission work for the individual lot and professional responsibilities before choosing a design.
For construction planning, evaluate how the design relates to the existing home, privacy, outdoor circulation, and usable space. Compare the building footprint with the way someone will actually enter and live in the unit.
Ask what the design package includes.
Before purchasing any plan or building package, clarify the deliverables, allowed modifications, professional services, and responsibilities for adapting it to the site. Ask how a change in windows, dimensions, or layout affects the package and review path.
Bring those answers into the contractor discussion. The estimate should explain which plans it uses, the assumptions about the site, and what additional work is outside the package. See our complete-project cost guide for a comparison framework.
Choose for the site and the occupant.
A standardized design is useful when it fits the household and property well. Test furniture, storage, daylight, privacy, and the relationship to the main residence. An attractive diagram should not decide the project before these practical questions are answered.
Explore our studio and bedroom layout guidance, detached ADU construction approach, and ADU permit preparation guide to connect a potential design to the full project.
Where to confirm information about preapproved plan options.
Preapproved plan options should be checked against current City and state pages; record the address, drawing, and date covered by the answer. For preapproved plan options, check the City of Costa Mesa ADU page, California HCD, and CSLB hiring guidance. For preapproved plan options, our Costa Mesa ADU Contractor homepage shows how it connects with the rest of the project.