Accessory dwelling unit construction cost — Rancho Cucamonga, 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 Rancho Cucamonga

Also serving nearby: Fontana · Ontario · Rialto · Jurupa Valley · Pomona

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More on this: HUD ADU resources — ADU policy and financing research.

Service area details

Serving all of Rancho Cucamonga — population 174,405; about 3,749 residents per square mile across 46.5 sq mi. ZIP codes covered include 91701, 91729, 91730, 91737, 91739.

Neighborhoods served in Rancho Cucamonga: Etiwanda Village, Gold Creek, Heritage Park, North Rancho, Victoria Woods — and every surrounding area.