Steps Involved in Building an ADU in California

Steps involved in building an ADU in California

Are you a California homeowner considering building an Accessory Dwelling Unit (ADU)? An ADU is a secondary living space on your property that can provide additional living space, generate rental income, or accommodate family members.

However, before diving into the construction process, it’s essential to understand the crucial factors that can make or break your ADU project.

In this article, we’ll share 12 expert tips to help you navigate the process and ensure a successful outcome.

Building an ADU

Tips on Steps Involved in Building an ADU in California

1. Property Development Standards & Regulations

California offers considerable flexibility when it comes to obtaining ADU permits, with a reduced waiting period of around 60 days for the approval process.

However, it’s crucial to consult local government officials to understand and comply with the specific standards in your area.

2. Address Privacy Concerns

Since ADUs are connected to the primary dwelling, privacy is a key consideration.

When building an ADU for family members, a communal living arrangement might work, but when leasing to tenants, privacy becomes paramount.

Ensure privacy by using window blinds, landscaping, and fencing. Formal agreements outlining property usage can also prevent potential conflicts.

3. Follow Design Guidelines

Align your ADU’s design with your existing home’s style to maintain cohesion and avoid reducing property value.

Keep in mind that design requirements vary between counties and cities, so compliance with local codes and regulations is essential.

Consult structural and MEP design experts or local building departments to ensure your ADU meets all necessary standards.

Building an ADU

4. Ensure Proper Access to the ADU

Accessibility and safety are crucial when building an ADU. Create a designated walkway and keep the passage between your home and the property line clutter-free. Consider separate entrances for attached ADUs to enhance privacy.

If an older family member will reside in the ADU, install wheelchair ramps and handrails to address their needs.

5. Comply with Fire Regulations

Fire safety is a top priority in ADUs. Consult local fire and building officials to understand and meet specific fire safety requirements, which may include mandatory sprinkler system installation.

Even if not required, installing a sprinkler system can enhance safety and potentially reduce insurance costs.

6. Assess the Site’s Condition

Before starting construction, understand your site’s conditions, such as slope, drainage issues, and soil quality.

Addressing these factors beforehand can help prevent future complications, cut costs, and ensure the longevity of your ADU’s foundation.

7. Plan Utility Connections

When planning your ADU, consider the necessary utility connections, including electricity, water, and sewage.

While tapping into your primary residence’s water source and gas lines is often convenient, you may need to upgrade or install a new sewage system to handle the increased load. If you plan to rent out the ADU, decide in advance how to handle utility costs.

Building an ADU

8. Choose the Appropriate Type of ADU

There are several types of ADUs to consider, each with its own unique characteristics:

Type of ADUDescription
Detached ADUNot connected to the main house, offers privacy
Attached ADUConnected to the main house, may have a separate entrance
Attached (Above Garage) AADUBuilt on top of the garage, saves space but requires extra work
Interior (Converted Garage) ADUTransforming an unused garage into a living space
Interior (Basement) ADUConverting a basement into an ADU, adds value to the home
Interior (Upper Floor) ADUTransforming unused bedrooms or playrooms into an ADU

9. Determine the Purpose of the ADU

Before starting construction, clearly define the purpose of your ADU.

Whether it’s a gym, home office, guest room, family member’s home, or a rental space for passive income, knowing the purpose will help guide your design and construction decisions.

10. Hire Professional Help

Building an ADU can be complex, so it’s essential to seek the help of local experts.

Find experienced local contractors who specialize in ADU construction to ensure your project is completed successfully and in compliance with all regulations.

11. Save Space with Efficient Design

When designing your ADU, consider space-saving solutions such as wall-mounted storage, compact appliances, and multi-functional furniture.

Avoiding bulky items and incorporating space-saving features will enhance the overall livability of your ADU.

Building an ADU

12. Consider Parking Requirements

Depending on your location, you may need to arrange a parking spot for your ADU.

However, exceptions may apply if your unit is near public transportation or in a historic area. Contact local officials to determine the specific parking requirements for your ADU.

FAQ On Steps Involved in Building an ADU in California

What are the zoning requirements for building an ADU in California?

In California, the regulations for building an ADU vary depending on the city or municipality. It is important to check with your local planning department to understand the specific zoning requirements in your area.

What are the steps involved in obtaining permits for an ADU?

The process of obtaining permits for an ADU in California can be complex and time-consuming. It typically involves submitting detailed plans, obtaining approval from various departments, and paying fees. Working with a qualified architect or contractor can help streamline the process.

Are there any financing options available for building an ADU?

There are several financing options available for building an ADU in California, including home equity loans, construction loans, and ADU-specific financing programs. It is important to research and compare the options to find the best fit for your project.

What are the construction requirements for building an ADU in California?

Building an ADU in California must comply with state and local building codes, including requirements for size, setbacks, and utilities. Working with a licensed contractor who is familiar with ADU construction can help ensure that your project meets all necessary requirements.


Building an ADU in California can be a rewarding experience, providing additional living space, rental income, or a home for family members. By following these 12 expert tips, you’ll be well-equipped to navigate the process and ensure a successful outcome.

Remember to consult professionals and local authorities throughout the project to ensure compliance with regulations and to create the ADU of your dreams.

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