What’s an ADU and is it right for me?

What is an Accessory Dwelling Unit (ADU) and why would I build one?

ADUs, also called granny flats, converted garages, or basement apartments, can help meet the changing needs of households while addressing the broader housing challenges in our counties.

An ADU is a flexible space that grows with your family. From space for your loved ones to supporting the community and building your retirement through renting, your ADU will grow with you.

Types of ADUs include:


Free-standing structure, such as a backyard cottage


Shares at least one wall with the primary home

Interior Conversion

Built from existing converted space (e.g., an attic or a basement)

Garage Apartment

Free-standing structure, such as a backyard cottage

Above Garage

Unit built above garage

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Junior ADU (JADU)

Under California state law, homeowners can now build both an ADU and a JADU on their property.

JADUs follow these guidelines:

“When you need an ADU, it’s already too late. It’s better to plan ahead of time and rent it out until a family member needs it.”

– Sonoma Resident

The benefits of building an ADU

Financial Security

Building an ADU gives you an additional revenue stream that can go toward reducing your cost of living, building your retirement, or creating more buffer for unexpected life events. Not only will you receive rental income in the short term, your sale price and property value can increase too.


Whether it provides a home for the immediate family, personal space for extended family or friends, a private home for parents, grandparents, or a family member with disabilities, or a return to home for grown children, an ADU can suit the needs of a variety of family situations.


An ADU provides you with flexibility, improving your options to remain in your community. Building an ADU can allow you to downsize and free up your main unit for rental, which can help you secure your retirement and provide more freedom as you age.

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By building an ADU or JADU, you’re investing in the future of your community

ADUs not only benefit homeowners, but help the community as well. Building ADUs helps to address the housing challenges in Napa and Sonoma Counties, and ADUs often provide homes for school teachers, firefighters, and other community members who otherwise may have to commute long distances from outside Napa and Sonoma Counties to find a home they can afford.

With many people still displaced from the fires, building and renting an ADU is a community service.

Explore case studies and get ideas for your ADU or Junior ADU

Check out photos, floor plans, and stories from your neighbors that have built ADUs and JADUs.

Explore ADU ideas

Tools and Resources

Step-by-step guidance

No matter what your needs are, access to quality, unbiased information is your right. Follow along as we provide essential information and resources to guide you at every stage of your journey.


HPP CARES CDE's accomplishments these past few years have been significant and all-encompassing; striving to advocate under the National Coalition for Equities’ umbrella to maintain a powerful community voice among the Federal and State regulators and major private sector corporations to address public policy issues, and to focus on the wealth & income inequality affecting affordable homeownership and small business growth. With the NCFE, HPP CARES CDE’s outreach efforts have led to an increase in corporate social responsibility and consumer protection. We have been able to reach more people, collaborate with more companies, meet with more regulators, all in the name of helping deserving individuals become sustainable homebuyers, successful small business owners, protected consumers and empowering California communities. HPP CARES CDE is at the forefront of helping people of color become partners in our mission to reduce income and wealth inequality and build stronger futures for all minority groups.