How to Get a Permit for Your Backyard ADU

Building a backyard ADU in California is one of the smartest moves homeowners can make today—whether it's for extra rental income, multigenerational living, or simply increasing property value. But before any construction begins, there's one essential step that causes confusion for many: how to get a permit for your backyard ADU.

Navigating city regulations, architectural plans, and inspections can feel overwhelming, especially for those going through it for the first time. The good news? With the right approach, the ADU permitting process can be manageable and even straightforward. Permits aren't just a legal formality—they're your blueprint for a safe, long-lasting, and fully compliant build.

Why Backyard ADUs Require Permits

Permits ensure that an ADU—no matter how small—meets California building codes, fire safety rules, and zoning laws. Skipping this step can lead to expensive fines, stop-work orders, and serious structural risks down the road.

Cities across California have embraced ADUs as a solution to the housing shortage, which has led to streamlined permit rules. However, that doesn’t mean permits are optional. Backyard ADUs still need to meet specific criteria related to lot size, setbacks, utilities, and more. Following the legal process from the start protects both the investment and the future use of the space—whether it’s for family, tenants, or resale.

Step-by-Step Guide to Getting a Backyard ADU Permit

The permit process varies slightly depending on the city or county, but the steps below offer a reliable roadmap.

1. Understand Your Property’s Zoning and Eligibility

The first step is to check local zoning regulations. In most California jurisdictions, single-family and multifamily residential zones are eligible for one or more ADUs. Some cities also allow both an ADU and a JADU on the same lot.

Key zoning factors include:

• Lot size and coverage limits

• Setback requirements (distance from property lines)

• Maximum square footage allowed

• Height limits and roof styles

• Parking requirements, if any

Local planning departments offer zoning maps and ADU-specific handouts that explain what’s allowed on a particular parcel. Consulting these resources upfront can save time and ensure the design is feasible.

2. Create Preliminary Design Plans

Once the zoning details are clear, the next step is to begin developing conceptual plans for the ADU. This includes:

• Floor plans

• Elevations (side views)

• Site layout (showing the ADU's location on the lot)

• Utility locations (water, sewer, gas, electric)

At this stage, it helps to work with a designer or builder familiar with local ADU codes. Professional guidance can prevent design errors that would otherwise delay the permitting process.

Pro tip: Simpler layouts tend to receive faster approvals. Detached ADUs with one or two bedrooms and a compact footprint often move through review more smoothly.

3. Submit the Permit Application

When the plans are finalized, they are submitted to the local planning and building departments—typically as part of a single permit application. Some cities offer streamlined ADU applications under state laws like SB 9 or AB 68, which require cities to approve qualifying ADU permits within 60 days.

A complete application package usually includes:

• Site plan and floor plan

• Structural details and materials list

• Energy calculations (Title 24 report)

• Drainage and grading plan (if required)

• Utility connection documentation

• Application forms and permit fees

Each city may have slightly different documentation requirements. Working with a consultant who’s handled multiple ADU projects in that jurisdiction often speeds things up considerably.

4. Respond to Plan Check Corrections

After submission, the plans are reviewed by multiple departments—planning, building, fire, and sometimes public works. Reviewers may return plan check comments requesting changes or clarifications.

This phase typically involves:

• Adjusting setbacks or window placement

• Clarifying structural calculations

• Modifying utility routing or venting systems

• Updating energy efficiency components

Responding to corrections quickly—and clearly—keeps the permit timeline on track. It’s also helpful to anticipate certain common requests based on local trends, which experienced ADU designers or builders often know in advance.

5. Obtain Final Permit Approval

Once the revised plans meet all department standards, the permit is issued. At this point, construction can begin—but only under the supervision of licensed contractors.

Keep in mind that the permit approval is not the end of the journey—it’s the foundation for moving forward legally. All work must match the approved plans, and any changes must be resubmitted for approval.

6. Schedule Required Inspections During Construction

During construction, a series of inspections must be passed before final sign-off. Typical inspections include:

• Foundation

• Framing

• Plumbing

• Electrical

• Insulation

• Roofing

• Final inspection (including safety and finishes)

Each inspection must be scheduled with the local building department. Missing or failing an inspection can cause costly delays, so it’s critical that the general contractor is experienced with city inspection processes.

7. Pass Final Inspection and Get Certificate of Occupancy

After all inspections are successfully completed, the building department issues a Certificate of Occupancy (CO). This confirms that the backyard ADU meets all health, safety, and building codes—and is legally ready for occupancy.

At this point, the ADU can be rented out, lived in, or listed as part of the property in official records. It's now a legal structure, contributing to property value and unlocking potential income.

What to Avoid During the Permit Process

Several common missteps can derail a backyard ADU project:

• Skipping professional help: Inexperienced DIY submissions often get rejected or delayed due to incomplete or incorrect documentation.

• Assuming all cities follow the same rules: Each jurisdiction applies state laws differently—what’s allowed in one may not be in another.

• Failing to coordinate utilities early: ADUs require dedicated connections for gas, water, sewer, and electricity. Start this coordination early.

• Building before permits are issued: Starting construction without permits can lead to stop-work orders, fines, and even demolition.

Permits: A Smart Step, Not a Burden

Permitting may seem like a bureaucratic hassle, but it serves as a crucial safety net for homeowners and their investment. Backyard ADUs are long-term assets, and going through the correct permitting process ensures:

• Safe and durable construction

• Higher resale value

• Legal rental income opportunities

• Insurance coverage and financial protection

California’s pro-ADU policies make it easier than ever to get permits—but homeowners still need to follow each step properly.

Final Thoughts: Building Right from the Ground Up

Adding a backyard ADU is one of the most rewarding ways to enhance a property, but the foundation begins with a solid permit. From zoning checks and plan designs to inspections and approvals, the process might seem complex—but with expert support, it becomes a clear and manageable path.

For those considering a backyard ADU, following the steps above can lead to faster approvals, fewer delays, and a finished space that adds real value.

If there are any questions about backyard ADU permits, the local process, or how to get started, drop a comment below and the team will answer ASAP with helpful insights.