Accessory dwelling unit construction cost — 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.
About this service
The cost to build an ADU depends on factors like your foundation type, utility connection distances, interior finish choices, and whether you are doing a detached build or a garage conversion. We provide an exact pricing confirmed free on the call.
Frequently asked in Costa Mesa
What is a modular accessory dwelling unit in Costa Mesa?
What makes the 'best' accessory dwelling unit in Costa Mesa?
Can I get accessory dwelling unit financing in Costa Mesa?
How do I find an ADU builder in Costa Mesa?
What ADU company should I choose in Costa Mesa?
What's the accessory dwelling unit permit process in Costa Mesa?
Where can I find an accessory dwelling unit near me 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 North, Mesa South, Westside Costa Mesa, Upper Newport Bay, Downtown Costa Mesa — and every surrounding area.
Areas we serve
Browse by state, then city.
California (3)
All of California · Costa Mesa · Jurupa Valley · Santa Maria