Cost to build accessory dwelling unit — Modesto, CA

Last updated: September 24, 2026

What affects the price

Building an ADU involves variables that shift your total investment. The footprint size and complexity of the architectural design are primary factors. Are you planning a detached unit that requires new utility trenching, or is this a garage conversion that uses existing plumbing? Site accessibility, soil conditions, and your choice of finishes—like luxury flooring versus standard options—also play significant roles. Permitting fees vary widely depending on your local municipality and current zoning requirements. Exact pricing confirmed free on the call.

About this service

The expense of building an ADU varies based on site preparation, whether you need to run new sewer or electrical lines, and the level of interior customization you choose. Larger custom builds naturally require more materials and labor than simpler conversions. We provide exact pricing confirmed free on the call.

Frequently asked in Modesto

Also serving nearby: Manteca · Tracy · Stockton · Merced · Antioch

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

Service area details

Serving all of Modesto — population 218,915; about 5,049 residents per square mile across 43.4 sq mi. ZIP codes covered include 95350, 95351, 95352, 95353, 95354, 95355, 95356, 95357.

Neighborhoods served in Modesto: Downtown Modesto, North Modesto, Salida, Keyes, Riverbank — and every surrounding area.