How to Get an ADU Permit in California: Step-by-Step Guide from the Field

Homeowners across California are jumping on the ADU (Accessory Dwelling Unit) trend—and for good reason. Whether it’s to generate rental income, create space for multigenerational living, or boost property value, ADUs are a smart move. But if there's one part that stops many before they even begin, it’s the permit process.

The good news? Getting an ADU permit doesn’t have to be a nightmare. When armed with the right information—and a few insider tips—it can be smooth, fast, and cost-efficient. This guide breaks down everything you need to know, step-by-step, with insight from over a decade of building and navigating California’s permitting system.

What Is an ADU Permit and Why Is It Required?

An ADU permit is an official approval from your local city or county that allows construction of an accessory dwelling unit on your property. It ensures your ADU meets California’s strict building codes, zoning laws, safety regulations, and design standards.

Skipping the permit? That’s risky. Unpermitted ADUs can lead to fines, legal troubles, insurance issues, and even forced demolition. Plus, an ADU with a permit adds far more value to your home.

Who Issues ADU Permits in California?

Permits are issued by local building departments or planning offices—typically the city or county in which the property is located. Each jurisdiction might have slightly different zoning rules and requirements, so it's essential to check local ordinances.

For example, what’s allowed in Los Angeles may differ from what’s allowed in San Jose. Fortunately, California state law sets baseline regulations that cities must follow, making the process more predictable statewide.

Step-by-Step Process to Get an ADU Permit

1. Check Your Zoning and Eligibility

Start by confirming that your property is zoned for an ADU. This includes reviewing:

• Lot size

• Setback requirements

• Parking rules (many areas now waive this)

• Number of units allowed (e.g., one ADU and one JADU per lot)

Zoning maps and ADU ordinances can usually be found on your city’s planning department website.

2. Prepare Preliminary ADU Plans

Work with a licensed architect or experienced ADU designer to prepare conceptual drawings that reflect your goals. These should include:

• Floor plans

• Elevations

• Site plan with dimensions

• Any planned utility upgrades

Professionally prepared plans are essential—not just for permit approval, but to avoid delays caused by revisions.

3. Pre-Application Meeting (Optional but Recommended)

Many California cities offer a free or low-cost pre-application meeting. This lets you review your plans with a city planner to spot potential red flags before formally applying. It can save weeks—sometimes months—of back-and-forth.

4. Submit the Permit Application

When ready, submit your full application package, which generally includes:

• Construction plans

• Title 24 energy compliance report

• Structural calculations (if required)

• Completed application forms

• Fees (which vary by city and ADU type)

Digital submissions are now common in most cities, but some may still require paper copies.

5. Plan Review and Revisions

City staff will review the application for compliance with local and state regulations. Expect questions or revision requests—this is normal. Respond quickly and clearly to keep your application moving forward.

Pro tip: Cities are required by law (per California Government Code 65852.2) to issue or deny permits within 60 days of a complete application. If you haven’t heard back, follow up.

6. Permit Approval and Issuance

Once approved, you’ll receive your official building permit—congratulations! You’re now legally authorized to start construction.

Common Pitfalls (and How to Avoid Them)

Incomplete Applications

Missing documents or vague plans are the top reasons for delayed permits. Always double-check the checklist provided by your local planning department.

Misinterpreting Zoning Laws

Each city interprets state law differently. Just because your friend got a 1,200 sq. ft. ADU doesn’t mean you can too. Consult with professionals who have experience in your area.

Ignoring Utility Requirements

Upgrades to electrical, water, or sewer systems are sometimes necessary—and costly. Plan for this early, especially if converting a garage or building a detached unit.

How Long Does It Take to Get an ADU Permit?

Most cities in California aim to process ADU permits within 60 days. However, real-world timelines range from 3 weeks to 4 months, depending on:

• The complexity of your project

• The city’s workload

• Whether revisions are required

Some cities offer “over-the-counter” permits for simple ADUs, especially interior conversions.

How Much Does an ADU Permit Cost?

Permit fees vary by jurisdiction and project size, but here’s a ballpark:

• Plan Check: $500 – $2,000

• Building Permit: $1,000 – $4,000

• Impact Fees: Waived for ADUs under 750 sq. ft. in most cities

Always budget for $3,000–$8,000 in total permit-related costs, just to be safe.

Tips to Speed Up Your ADU Permit

• Hire Local Experts: They know the local codes and city staff.

• Avoid “Stock Plans” Without Customization: Each site is unique.

• Don’t Delay Revisions: Respond quickly to plan check comments.

• Use Pre-Approved Plans If Available: Some cities like San Jose or LA offer them.

Final Thoughts: Building Smarter, Not Slower

Getting an ADU permit in California is more accessible than ever—but only if approached with the right knowledge and preparation. With clear goals, professional plans, and local code awareness, the permitting process can move faster and with fewer headaches.

And remember: a permitted ADU isn’t just a second unit—it’s peace of mind, legal protection, and added long-term value.

If there are any questions or specific challenges being faced in the ADU permitting process, feel free to drop them in the comments section below. Responses are quick and personalized—because every successful project starts with clarity.