Local adu — Costa Mesa, CA
Last updated: September 24, 2026
What affects the price
Building an ADU involves several moving parts that shape your total investment. The final figure depends heavily on whether you choose a prefab unit or a custom build from the ground up. Site conditions are another major factor; if your property requires extensive grading, utility trenching, or foundation work, costs will climb. You also have to consider your choice of finishes, like high-end appliances or custom cabinetry. Navigating local permit fees and impact assessments also adds to the total.
Frequently asked in Costa Mesa
What are the requirements for an ADU unit in Costa Mesa?
How does ADU building work in Costa Mesa?
What are the costs associated with building an ADU in Costa Mesa?
What are the benefits of a backyard accessory dwelling unit in Costa Mesa?
How do I find the best ADU builder in Costa Mesa?
What is the cost to build an accessory dwelling unit in Costa Mesa?
Also serving nearby: Santa Ana · Huntington Beach · Westminster · Irvine · Garden Grove
More on this: HUD ADU resources — ADU policy and financing research.
Service area details
Serving all of Costa Mesa — population 108,354; about 6,855 residents per square mile across 15.8 sq mi. ZIP codes covered include 92626, 92627, 92628.
Neighborhoods served in Costa Mesa: Mesa del Mar, The Westside, South Coast Metro, Fairview Shores, Upper Newport Bay — and every surrounding area.
Areas we serve
Browse by state, then city.
California (3)
All of California · Costa Mesa · Jurupa Valley · Santa Maria