ADU Permits in California: Everything You Need to Know

Accessory dwelling units (ADUs) are steadily gaining popularity, in large part due to recent state legislation. However, despite these developments, acquiring ADU permits in California will always be necessary, which tends to be a challenge for most homeowners.

In this guide, we will explain everything you need to know about ADU permitting in California. Whether you want to invest in a detached ADU behind your primary dwelling or convert your garages into living spaces, this guide will provide a ton of value.

Understanding ADU Permits

ADU permits are legal documents that authorize the construction or conversion of an ADU on your property in line with specific state and local regulations. This permit ensures your ADU meets safety, zoning, and design standards set by your local jurisdiction.

What are the most commonly required ADU permits?

To successfully build an ADU, you will require the following permits:

Building permit

Once you obtain planning and zoning permits, a requirement in many cities, the next step is getting the building permit. This permit ensures your ADU plans, covering the foundation, framing, electrical, and plumbing systems, meet code standards. It’s essential for starting construction.

Electrical and plumbing permit

You’ll need an electrical permit to install electrical elements in the ADU, covering wiring, outlets, lighting, and panel installations. This permit ensures that the ADU’s electrical systems adhere to safety norms and electrical codes.

For any plumbing work, like setting up or altering water lines, drainage, fixtures, and appliances, plumbing permits are required. They certify that the plumbing work in the ADU is properly done, reducing leak risks and health hazards.

Local permits

As the name suggests, local permits are specific to each city or county in the state. As a homeowner in California, you can acquire these permits from your community’s planning and building divisions.

These permits typically involve zoning, excavation, grading, and environmental impact. For instance, if your site exists within a geohazard zone like San Jose, you will require a special clearance as part of your ADU permit checklist.

What do you need to apply for a permit?

Here is what you will typically need to apply for ADU permits in California:


  • Completed permit application form


  • Proof of property ownership


  • Site plans of your current space


  • Detailed ADU construction plans


  • Payment for permit fees


After you pay the required fees, there is a 60-day timeframe within which the local government will either approve or reject your proposal. As it happens, this is where homeowners face significant delays, either with payment processing or other technical errors.

At GoldenADU, we understand that acquiring ADU permits in California is already a daunting task. With the additional delay, it can become downright frustrating. With our expertise in ADU building and familiarity with the permitting process, we can make this uphill battle much easier for you.

Contact us today at 213-693-2405 to get your free ADU consultation and learn how we can help you breeze through the permitting process!

Frequently Asked Questions (FAQs)

How much does an ADU permit cost in California?

The cost of an ADU permit in California depends on your location and the size of your ADU. In general, building permits range from $2,000 to $10,000, while city fees can range from $3,000 to $11,000.

How long does it take to get an ADU permit in California?

It can take up to 60 days to get an ADU permit in California. Within the 60-day timeframe, your local government can either accept or reject your ADU proposal.

What is the maximum square footage for an ADU in California?

The maximum square footage for an ADU in California is 1,200 square feet for most cities. However, it can depend on local ADU ordinances as well as the size of the primary dwelling.

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