How to build an ADU in San Jose, CA

Learn the city’s guidelines for adding an accessory dwelling unit (ADU) to your property.

A tiny home, or accessory dwelling unit, in a backyard.

The tiny house movement is coming to San Jose.

Photo via the City of San José Department of Planning, Building & Code Enforcement

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We don’t have to tell you that San Jose has one of the most challenging housing markets in the US. Due to serious housing shortages, many locals + politicians are considering tiny homes, or accessory dwelling units (ADUs), as part of the solution. 💡

Whether you’re interested in adding an ADU for extended family or supplemental rental income, here is our breakdown of San Jose’s guidelines to get started. ✅

🏠 What qualifies as an ADU?

Also known as secondary units, in-law units, granny flats, or backyard cottages — San Jose officials define an ADU as small living units with a kitchen + bathroom on properties zoned for a single-family home, duplex home, or multi-family building. This can include tiny homes on wheels (THOW), and garage + basement conversions.

🔨 Can I build one on my property?

Before you start shopping for lumber, the City has prepared detailed checklists for ADUs and THOWs to determine whether your tiny dream aligns with city zoning and fire codes.

Once you’re in the clear, you can speed up the construction process by exploring one of San Jose’s pre-approved vendors who offer standardized construction plans + builders. Be sure to review city requirements, forms + checklists as you finalize your plan and apply for permits.

💸 How much will it cost me?

ADU costs range from $80,000-$250,000 depending on size, type, existing plumbing, etc.

Working with pre-approved vendors will save money, but financing can be tricky. Instead of standalone loans, some realtors recommend taking out a Home Equity Line of Credit that leverages the equity of the primary residence.

Some homeowners with low or moderate income may also qualify for the CalHFA ADU Grant, which could provide up to $40,000 towards the cost of an ADU.

🔎 Where can I learn more?

Check out San Jose + California‘s webpages for more information. Housing Trust Silicon Valley also offers free educational workshops for those interested in building an ADU.

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