Step-by-Step Guide to Building an ADU in California: What You Need to Know

Step-by-Step Guide to Building an ADU in California: What You Need to Know


Accessory Dwelling Units (ADUs) are gaining popularity in California as an effective solution to the housing crisis. These secondary housing units offer homeowners the opportunity to increase property value, generate rental income, and contribute to the state’s housing supply. If you’re considering building an ADU in California, this step-by-step guide will walk you through the process, from understanding the regulations to completing the construction. By the end of this article, you’ll have a clear roadmap to turn your ADU dream into a reality.

Understanding California’s ADU Regulations

Before you start planning your ADU project, it’s crucial to familiarize yourself with California’s ADU regulations. In 2020, the state enacted several laws aimed at simplifying ADU construction. These laws include Assembly Bill 68 (AB 68), Senate Bill 13 (SB 13), and Assembly Bill 670 (AB 670), which collectively make it easier for homeowners to build ADUs on their properties. It’s essential to research the specific regulations in your city or county, as they may have additional requirements or restrictions.

Determine ADU Type and Size

One of the first decisions you’ll need to make is the type and size of your ADU. ADUs can be attached, detached, or converted from existing space like a garage or basement. Determine the best location on your property for your ADU, keeping in mind factors like zoning laws, available space, and accessibility. Additionally, you’ll need to decide whether you want a Junior ADU (JADU), which is a smaller, self-contained unit with specific requirements. The size and type of ADU you choose will impact the design and construction process.

Create a Budget and Secure Financing

Building an ADU requires a financial commitment. Start by creating a budget that outlines all the costs associated with your project, including construction, permits, utilities, and landscaping. Depending on your location and the size of your ADU, costs can vary widely. To secure financing, explore options like personal savings, home equity loans, construction loans, or ADU-specific financing programs. It’s essential to have a clear understanding of your budget before moving forward.

Obtain the Necessary Permits

In California, ADU regulations have been streamlined to make obtaining permits more straightforward. However, you’ll still need to obtain the necessary permits from your local government. Begin by submitting your ADU plans and permit applications to the relevant authorities. The permitting process may involve zoning review, environmental assessments, and inspections. Be prepared for potential delays and ensure that your ADU plans comply with all building codes and regulations.

Design and Build Your ADU

Once you’ve obtained the necessary permits, it’s time to design and build your ADU. You can work with an architect or design professional to create plans that meet your specific needs and preferences. During this phase, consider the layout, energy-efficient features, and accessibility features, as they can impact the functionality and marketability of your ADU. After finalizing the design, hire a qualified contractor to begin construction. Ensure that the construction process adheres to your budget and timeline, and monitor progress closely.

Finishing Touches and Rental Considerations

After the construction phase, it’s time for the finishing touches on your ADU. This includes interior design, landscaping, and any necessary utilities connections. Depending on your intended use for the ADU, you may need to consider rental management, such as screening tenants, setting rental rates, and creating rental agreements. Remember that in California, ADUs are commonly used as rental properties, providing additional income for homeowners.


Building an ADU in California can be a rewarding and profitable endeavor, but it requires careful planning and adherence to regulations. By understanding the state’s ADU laws, determining the type and size of your unit, creating a realistic budget, securing financing, obtaining permits, and overseeing the construction process, you can successfully build an ADU that meets your needs and contributes to the state’s housing supply. With the housing crisis ongoing, ADUs offer an opportunity for homeowners to make a positive impact while reaping the benefits of increased property value and rental income. So, take the plunge and turn your ADU vision into reality, contributing to California’s housing solution.


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