How to Apply for an ADU Permit: A Complete Checklist

So, you’re ready to build an Accessory Dwelling Unit (ADU)—but navigating the permit process feels overwhelming. Questions like “Where do I even start?” or “What documents do I need?” often leave homeowners stuck before the project even begins. The truth is, applying for an ADU permit doesn’t have to be complicated. With the right checklist and a bit of preparation, the process becomes manageable—and even exciting.

Permitting is one of the most important early steps in building an ADU. Whether it's a garage conversion, detached unit, or basement transformation, getting the green light from the city ensures everything is up to code and safe for long-term use. Here’s a full breakdown of what’s needed to apply for an ADU permit—straight from the experience of working with hundreds of homeowners across California.

What Is an ADU and Why Is a Permit Needed?

An Accessory Dwelling Unit (ADU) is a smaller, independent residential unit located on the same lot as a primary residence. These structures have gained popularity due to housing shortages, rental income potential, and multigenerational living needs.

But before a single nail goes into the wall, a building permit is required. This is not just a formality—it's a safeguard. Permits ensure that your ADU meets local zoning, safety, environmental, and building standards. Without it, homeowners risk fines, legal issues, or having to demolish the unpermitted structure later.

The Complete ADU Permit Checklist

1. Understand Local Zoning and Regulations

Every city and county has its own ADU rules. Some allow two units per lot, others only one. Some areas have minimum lot sizes or height restrictions. Before submitting anything, check with your local planning or building department.

California has statewide ADU laws that allow homeowners to build units more freely, but cities still set specifics like setbacks, height limits, and parking requirements. Cities like Los Angeles, San Diego, and San Jose also offer helpful online zoning checkers.

Checklist Tip:

• Call or visit your city’s planning department to confirm your lot is eligible.

• Ask about size limits, setbacks, and any historic district or flood zone restrictions.

2. Hire a Design Professional or ADU Consultant

Whether it’s an architect, drafter, or ADU-specific designer, hiring a professional who understands local code will save time and headaches. They’ll create site plans, floor plans, elevations, and energy compliance reports—all of which are required in your permit packet.

Professionals familiar with the California Building Code (CBC) and Title 24 energy requirements will ensure your design won’t get kicked back during review.

Checklist Tip:

• Confirm your designer has experience with local ADU approvals.

• Ask for digital copies of all drawings—most cities now require online submissions.

3. Prepare Your Site Plan and Construction Drawings

A complete permit package must include detailed drawings of the property and the planned ADU. These typically include:

• Site plan (showing lot, ADU location, setbacks, and utilities)

• Floor plans with room dimensions

• Roof plan and elevations

• Electrical and plumbing layout

• Title 24 energy compliance documentation

• Foundation and framing details

Ensure that every sheet is labeled, drawn to scale, and aligned with your city’s submittal standards.

Checklist Tip:

• Some cities offer “permit-ready” ADU plans—ask if yours does.

• Include a legend or code references directly on the drawings when possible.

4. Submit the Permit Application

Most cities now use an online portal for permit submissions. You’ll need to create an account, upload documents, and pay a plan check fee. The application usually asks for:

• Property address

• Parcel number

• Contact info for owner and applicant

• Type of ADU (attached, detached, conversion)

• Estimated construction value

Depending on the city, review can take anywhere from 2–8 weeks.

Checklist Tip:

• Double-check file formats—PDF is usually required.

• Clearly name all files to match city guidelines (e.g., “Sheet A1 - Site Plan”).

5. Respond to Plan Check Comments

After review, expect to receive a list of corrections or clarifications. This is completely normal—even well-prepared applications often require revisions. The city may ask for:

• Clarification on fire separation between units

• Updated utility service plans

• Adjusted structural details

• Stormwater or grading info

Make the requested changes promptly and resubmit. Once approved, you’ll receive your building permit, and construction can legally begin.

Checklist Tip:

• Keep a log of all comments and responses to avoid repeated issues.

• Many jurisdictions allow partial approvals—ask about phased permits if needed.

6. Pull Utility and Encroachment Permits

In some cases, additional permits are needed beyond the building permit. These might include:

• Sewer connection permit

• Electrical service upgrade

• Water meter or backflow prevention

• Curb cut or driveway expansion

Coordination with utility companies may be required. Be proactive about this step—delays in utility permits often hold up the entire project.

Checklist Tip:

• Ask your city for a utility coordination checklist.

• Submit applications for utility upgrades as soon as building permits are close to approval.

7. Schedule Inspections During Construction

Once construction begins, inspections must be scheduled at key stages. These typically include:

• Foundation inspection

• Framing inspection

• Plumbing and electrical rough-in

• Insulation and drywall

• Final walk-through

Each inspection must be passed before moving to the next phase. Failing to call for inspections—or failing an inspection—can delay the project and trigger costly fixes.

Checklist Tip:

• Book inspections a few days in advance; some cities have limited availability.

• Post the permit card visibly on-site as required.

8. Obtain Final Sign-Off and Certificate of Occupancy

After the final inspection is passed, the building department will issue a Certificate of Occupancy (CofO). This document legally allows the ADU to be occupied. Without it, renting or living in the unit is prohibited.

Keep this certificate in your records—it may be needed for insurance, refinancing, or future resale.

Checklist Tip:

• Take final photos of the completed unit and CofO for your own documentation.

• Notify your insurance provider that a new livable unit is on the property.

Extra Tips from the Field

Over the past decade, a few strategies have consistently helped homeowners succeed with their ADU permitting:

• Start with a feasibility study: This upfront research can identify challenges like easements or tree protections that could impact design.

• Communicate with neighbors: While not always required, transparency often prevents complaints later.

• Track timelines: Some cities are legally required to respond to ADU applications within 60 days. If delayed, a polite follow-up may help.

• Consult professionals early: A good ADU consultant or permit specialist can often reduce turnaround times by weeks.

These insights come from real projects in cities like Oakland, Sacramento, and Santa Clara—each with its own quirks, but all governed by California’s state-level ADU framework.

Final Thoughts

Applying for an ADU permit may feel like a maze at first, but with the right preparation and clear checklist, the process becomes far more manageable. It all starts with understanding local requirements, assembling complete documentation, and responding quickly to city feedback. By working with experienced professionals and following a proven workflow, homeowners can secure permits efficiently and start building with confidence.

Have any questions about applying for an ADU permit or navigating your city’s requirements? Leave a comment below, and a team member will respond as soon as possible with expert, tailored guidance.