How to Get an ADU Permit and Legalize Existing Units in San Diego

About the figures in this article. These are general San Diego market ranges for planning purposes — they are not a quote from Fortune Design & Permits. They were carried over from earlier articles, have not been reviewed against current costs, and should be treated as indicative only. Ask us for a quote on your property.

With the growing demand for housing in Southern California, many homeowners in San Diego are turning to Accessory Dwelling Units (ADUs) as a practical solution. Whether you’re planning to build a new unit or already have an unpermitted structure, understanding how to obtain an ADU permit and legalize existing units is essential.

San Diego has introduced some of the most ADU-friendly regulations in California, but the process still requires careful planning, proper documentation, and compliance with city requirements. If you want to avoid fines, delays, or complications, it’s important to follow the correct steps.

In this guide, we’ll walk you through how to secure an ADU permit and bring existing units into compliance in San Diego.

What Is an ADU Permit?

An ADU permit is official approval from the City of San Diego that allows you to legally construct, convert, or maintain an accessory dwelling unit on your property.

This permit ensures your ADU meets:

Local zoning regulations
Building and safety codes
Fire and accessibility standards
Energy efficiency requirements

Without a valid permit, your ADU may be considered illegal, which can create serious issues when renting, refinancing, or selling your property.

Why Legalizing an Existing Unit Matters

Many San Diego homeowners have older garage conversions or backyard units that were built without permits. While these structures may function well, they can create legal and financial risks.

Legalizing your ADU provides:

Protection from code violations and penalties
The ability to rent the unit legally
Increased property value
Easier refinancing or sale of your home
Peace of mind knowing your structure meets safety standards

The City of San Diego has programs that encourage homeowners to bring unpermitted units into compliance.

Step-by-Step Process to Get an ADU Permit in San Diego

Obtaining an ADU permit involves several steps, but with proper planning, the process can be smooth and efficient.

1. Evaluate Your Property

The first step is determining whether your property qualifies for an ADU.

Key factors include:

Zoning designation
Lot size and layout
Existing structures
Setback requirements

Most residential properties in San Diego are eligible, but each property has unique conditions that must be assessed.

2. Choose the Type of ADU

You’ll need to decide what type of ADU you want to build or legalize:

Detached ADU
Attached ADU
Garage conversion
Junior ADU (JADU)

Your choice will affect design, cost, and permit requirements.

3. Prepare ADU Plans

To apply for a permit, you must submit detailed plans, including:

Site plan showing property layout
Floor plans with dimensions
Elevations and exterior design
Structural details
Energy compliance documentation

Accurate and complete plans are critical for approval.

4. Submit Your Permit Application

Once your plans are ready, they are submitted to the City of San Diego for review.

The city will:

Check compliance with zoning laws
Review structural and safety elements
Evaluate energy efficiency standards

California law requires cities to respond within 60 days, but incomplete applications may take longer.

5. Address Plan Check Corrections

It’s common for the city to request revisions during the review process.

These corrections may involve:

Adjusting design elements
Providing additional documentation
Clarifying structural details

Responding quickly helps keep your project on schedule.

6. Receive Permit Approval

Once all requirements are met, your ADU permit is approved, and you can begin construction or finalize legalization.

How to Legalize an Existing ADU in San Diego

If you already have an unpermitted unit, the process is slightly different but still manageable.

1. Property Inspection

The city may require an inspection to evaluate the existing structure.

This helps determine:

Structural integrity
Safety compliance
Required upgrades

2. Create As-Built Plans

For legalization, you’ll need “as-built” drawings that reflect the current structure.

These plans document:

Layout and dimensions
Electrical and plumbing systems
Structural components

3. Submit Permit Application

You’ll submit your ADU permit application along with the as-built plans.

4. Make Required Upgrades

If the unit does not meet current codes, upgrades may be required, such as:

Electrical or plumbing improvements
Fire safety enhancements
Structural reinforcements

5. Final Approval and Certification

After completing any required updates, the city will issue final approval, and your unit will be legally recognized.

Cost of ADU Permits and Legalization

The cost of obtaining an ADU permit or legalizing an existing unit depends on several factors.

Typical Permit Costs

City permit fees: $3,000 – $8,000
Plan preparation: $5,000 – $12,000
Engineering and reports: $2,000 – $7,000

Legalization Costs

Legalizing an existing unit may involve additional expenses:

Inspections: $500 – $2,000
Upgrades and repairs: $5,000 – $25,000+
Plan revisions: varies

Common Challenges in the ADU Permit Process

While San Diego has simplified ADU regulations, homeowners may still face challenges such as:

Understanding zoning requirements
Preparing accurate plans
Managing permit timelines
Addressing code compliance issues
Coordinating multiple steps of the process

Working with professionals can help avoid these obstacles.

Tips for a Smooth ADU Permit Process

To improve your chances of success:

Start with a professional property evaluation
Submit complete and accurate plans
Respond quickly to city feedback
Work with experienced ADU specialists
Plan for potential revisions

These steps can significantly reduce delays and costs.

Why Work with Fortune Design & Permits

Navigating the ADU permit process or legalizing an existing unit can be complex, especially without the right experience. At Fortune Design and Permits, we specialize in helping homeowners simplify the process and achieve approval efficiently.

Our services include:

Property feasibility analysis
Custom ADU design and planning
Permit application and coordination
Legalization of unpermitted units
Full project support from start to finish

We understand San Diego’s regulations and help ensure your project meets all requirements.

Final Thoughts

Getting an ADU permit or legalizing an existing unit in San Diego is an important step toward protecting your property and maximizing its value. While the process involves multiple stages, proper planning and expert guidance can make it manageable and efficient.

Whether you’re building a new ADU or bringing an existing unit into compliance, taking the right approach ensures long-term benefits and peace of mind.