Step By Step ADU Permit Process California

The Complete Step-by-Step ADU Permit Process in California

Permits, Plans & Process
September 13, 2025•5 min read

Accessory Dwelling Units (ADUs) have become one of the fastest-growing ways for California homeowners to expand living space, create rental income, and add long-term property value. But before you can start building, one critical step stands between your idea and reality: the ADU permitting process.

Understanding the permit process can feel overwhelming. Cities have their own rules, paperwork can be confusing, and missing a single requirement can delay or even halt your project. On top of that, neighbors or homeowners’ associations (HOAs) may have questions or concerns, adding another layer of complexity.

This guide is designed to take you through the step-by-step ADU permit process in California, from initial planning to final inspection. You’ll learn what documents you need, which local offices to work with, and how SBKN Engineering can streamline the process for you. By the end, you’ll feel confident moving forward with your ADU project while avoiding common mistakes.

Step 1: Determine If Your Property Qualifies for an ADU

Before you dive into drawings or applications, you need to know if your property is eligible for an ADU. Most California single-family lots can host an ADU, but requirements vary by city.

Key Considerations:

  1. Lot Size: Some municipalities require a minimum lot size to build an ADU.

  2. Zoning Restrictions: Check your city’s zoning code to ensure ADUs are allowed on your property type.

  3. Setbacks & Height Limits: Every ADU must comply with local building setbacks (distance from property lines) and height restrictions.

  4. Utilities & Infrastructure: Make sure your property can support the plumbing, electrical, and sewer connections for an additional unit.

SBKN Engineering Tip: We often conduct a preliminary site evaluation to confirm your property meets all ADU eligibility requirements. This step can save time and prevent costly redesigns later.

Step 2: Understand California’s ADU Laws

California has passed several laws to encourage ADU construction. Knowing these regulations can help you avoid unnecessary delays and rejections.

Important Laws to Know:

  • AB 68 & AB 881 (2020): Streamlined permit approvals for ADUs and junior ADUs (JADUs).

  • SB 13 (2020): Eliminates impact fees for smaller ADUs and limits cities from imposing unnecessary restrictions.

  • SB 9 (2021): Expands opportunities to create additional units on single-family lots.

What These Laws Mean for Homeowners:

  • Cities are required to approve qualifying ADUs within 60 days of application.

  • Fees are limited for smaller units, reducing project costs.

  • Local restrictions cannot override state law unless they are essential for safety or infrastructure.

SBKN Engineering Tip: Staying current on these laws ensures your project takes advantage of incentives and avoids unnecessary roadblocks.

Step 3: Prepare Your ADU Plans

Once you confirm eligibility, the next step is creating construction-ready plans. This is where many homeowners run into problems. Incomplete or inaccurate plans can lead to permit delays.

Essential Elements of ADU Plans:

  1. Site Plan: Shows your property layout, existing structures, setbacks, and proposed ADU location.

  2. Floor Plan: Detailed layout of rooms, doors, windows, and dimensions.

  3. Elevations: Front, rear, and side views of your ADU with height measurements.

  4. Mechanical & Electrical Plans: Shows plumbing, electrical, and HVAC layouts.

  5. Engineering Documents: Structural calculations, grading, and foundation design (required for most ADUs).

SBKN Engineering Tip: We provide stamped, professional plans that meet city requirements, reducing the likelihood of permit rejections. Having professional engineering documents also reassures neighbors and HOAs that the project is safe and compliant.

Step 4: Submit Your Permit Application

After your plans are ready, it’s time to submit your permit application.

Typical Steps:

  1. City Planning Department: Submit your site, floor, and elevation plans for zoning approval.

  2. Building Department: Includes building, mechanical, electrical, and plumbing permits.

  3. Other Departments: Fire, water, or environmental departments may review if your city requires it.

Tips for Smooth Submission:

  • Make sure all forms are complete and signed.

  • Include all supporting documents (plans, structural calculations, impact fee payments if required).

  • Check the city’s online portal for electronic submission options.

SBKN Engineering Tip: We often handle the full submission process for clients, ensuring nothing is missed and questions from the city are answered promptly. This can reduce approval time significantly.

Step 5: Address Corrections or Comments

It’s common for cities to issue a correction list after reviewing your application. This is not a rejection—it’s an opportunity to fix minor issues.

Common Corrections:

  • Adjusting setbacks or lot coverage.

  • Clarifying window placement for privacy.

  • Updating mechanical, electrical, or plumbing schematics.

  • Submitting additional engineering calculations.

SBKN Engineering Tip: Our team responds to corrections quickly, often revising plans and resubmitting within days, keeping your project timeline on track.

Step 6: Permit Approval

Once the city accepts all revisions, you’ll receive your official ADU permits. At this stage:

  • Review all conditions of approval carefully.

  • Make sure permits are posted at the construction site as required.

  • Confirm fees are paid.

SBKN Engineering Tip: We always verify that all permits are in order and help clients schedule inspections with the city to prevent delays once construction begins.

Step 7: Begin Construction

With permits in hand, construction can begin.

Key Points:

  • Hire licensed contractors familiar with ADU projects.

  • Schedule inspections according to your city’s requirements.

  • Keep neighbors informed to reduce complaints.

SBKN Engineering Tip: We offer construction oversight and support, ensuring your project is built according to approved plans and passes all inspections.

Step 8: Inspections & Final Approval

Cities require inspections at various stages:

  • Foundation inspection

  • Framing inspection

  • Electrical, plumbing, and mechanical inspections

  • Final inspection

Passing all inspections results in your Certificate of Occupancy, officially allowing you to use your ADU.

SBKN Engineering Tip: Our team coordinates with inspectors and contractors to ensure smooth approvals and addresses any issues that arise on-site quickly.

Conclusion

Building an ADU in California can seem complicated, but by following a step-by-step process, homeowners can avoid delays and frustrations.

Key takeaways:

  1. Confirm property eligibility and understand local laws.

  2. Prepare thorough, professional plans.

  3. Submit a complete permit application and address corrections promptly.

  4. Oversee construction and inspections carefully.

At SBKN Engineering, we specialize in guiding homeowners through every stage of the ADU process. From initial site evaluation to stamped engineering plans, permit submission, and construction oversight, we make sure your ADU project is smooth, compliant, and successful.

👉 Ready to start your ADU project? Contact SBKN Engineering today for expert design, permitting, and project support.

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