Cost to build accessory dwelling unit

Looking for cost to build accessory dwelling unit in San Jose, CA? Call AccessoryDwellingUnit Experts 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 is a major project, and the final bill depends on a few key things. Site prep is a big factor; if your land is sloped or needs extensive utility connections, costs go up. The materials you choose—from siding to kitchen finishes—also change the math significantly. Whether you’re building a detached unit or converting an existing garage shifts the permit requirements and structural work needed. We provide exact pricing confirmed free on the call.

About this service

Building an ADU involves costs for permits, site prep, foundation, framing, plumbing, and electrical work. Prices fluctuate based on whether you choose a custom design or a pre-planned layout, as well as the complexity of connecting to existing city utilities. Exact pricing confirmed free on the call.

Frequently asked in San Jose

What are the disadvantages of ADUs?

Disadvantages can include upfront construction costs and potential impacts on your current property's yard space. You might also face a longer permitting process depending on your specific location in San Jose. It's essential to weigh these against the benefits before proceeding with your project.

How much does an ADU cost in California?

The cost to build an ADU in California, including San Jose, varies significantly based on size, materials, and site preparation. Factors like foundation work, utility connections, and finishing touches all contribute to the final price. A professional quote will break down these elements for your specific project.

What are the rules for ADUs in California?

California has statewide ADU laws that streamline approvals, but local San Jose ordinances may add specific requirements. These often relate to setbacks, height limits, and parking. Understanding these rules is crucial for a smooth building process.

Is an ADU allowed in Maryland?

This information is for San Jose, California. For Maryland, you would need to consult local regulations specific to that state and its cities regarding ADU allowances and requirements.

What are the rules for ADUs in California?

California generally encourages ADU development with streamlined approval processes. However, specific rules regarding setbacks, lot coverage, and parking can vary by city, including San Jose. Consulting with local experts familiar with these regulations is recommended.

While various grant programs have existed or been proposed in California to help with ADU costs, specific details and availability can change. It's best to inquire about current programs when you speak with a professional for your San Jose ADU project.

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, Berryessa, Downtown San Jose — and every surrounding area.