Best 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.

About this service

Defining the best unit for your property depends on your specific goals, such as maximizing rental yield or creating a versatile multi-generational living space. A great build features high-quality insulation, smart storage solutions, and an aesthetic that complements your main house. We emphasize durable construction and efficient design to ensure your unit remains a valuable asset for your property over the long term. Let us help you plan the right layout. Exact pricing confirmed free on the call.

Frequently asked in Costa Mesa

Also serving nearby: Santa Ana · Huntington Beach · Westminster · Irvine · Garden Grove

All cities in California →

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, South Coast Metro, The Westside, Upper Newport Bay, The Village — and every surrounding area.