Accessory dwelling unit construction cost

Looking for accessory dwelling unit construction cost in San Jose, CA? Call AccessoryDwellingUnit Solutions for a contact a provider — no obligation. Licensed adu builders serve San Jose and the surrounding area, and you'll get straight answers on timing and what affects the price.

Last updated: September 24, 2026

What affects the price

Building an ADU involves several moving parts that shape your total budget. The biggest factor is whether you choose a prefabricated unit or a custom build on-site. Site preparation is also significant; if your land requires extensive grading, utility trenching, or foundation work, costs will climb. Your choice of finishes—like kitchen cabinetry, flooring, and siding materials—also shifts the bottom line. We help you navigate these variables to find a setup that fits your property. Exact pricing confirmed free on the call.

About this service

The cost of building an ADU depends on your choice of materials, the square footage, and whether you are doing a garage conversion or a new detached build. Site access and utility upgrades also play a big role in the final bill. Exact pricing confirmed free on the call.

Frequently asked in San Jose

What are the disadvantages of ADUs?

How much does an ADU cost in California?

The cost of an ADU in California, including San Jose, varies significantly based on size, materials, and site conditions. Factors like foundation type and finishes play a big role. The best way to get an accurate figure for your specific project is to get a personalized quote.

What are the rules for ADUs in California?

California has state-level ADU laws that set minimum standards, but local jurisdictions like San Jose can have additional requirements. These often pertain to setbacks, lot coverage, and parking. We can help you understand how these rules apply to your property.

Is ADU allowed in Maryland?

This service focuses on California. For information on ADU regulations in Maryland, you would need to consult local resources specific to that state. Our expertise is rooted in California's building and zoning codes.

California has offered various grant programs to encourage ADU development, though specific programs and funding levels change. Eligibility often depends on factors like income and whether the ADU will be rented at affordable rates. Inquire during your consultation for current information.

What are the rules for ADU in California?

California's ADU laws aim to streamline approvals and increase housing options. Key aspects involve size limitations, owner-occupancy requirements, and permitting processes. San Jose adheres to these state mandates while also having its own local considerations to address.

Also serving nearby: Burbank · Santa Clara · Sunnyvale · Fremont · Hayward

All cities in California →

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

Service area details

969,655residents

5,449per sq mile

8ZIP codes served

Serving all of San Jose — population 969,655; about 5,449 residents per square mile across 177.9 sq mi. ZIP codes covered include 95025, 95101, 95103, 95106, 95108, 95109, 95110, 95111.

Neighborhoods served in San Jose: Willow Glen, Almaden Valley, Japantown, Rose Garden, Downtown San Jose, Berryessa — and every surrounding area.