The Complete ADU Process in Greater Los Angeles: From Design to Permit Approval

Building an Accessory Dwelling Unit (ADU) involves much more than construction. Before work can begin, homeowners typically move through several stages, including planning, design, permitting, and agency review. While California ADU laws apply throughout the state, the permitting process can vary depending on the city or jurisdiction. For homeowners in the Greater Los Angeles area, understanding the process can help set realistic expectations and create a smoother path from concept to construction.

Whether the goal is to generate rental income, create housing for family members, or add flexible living space, proper planning early in the process can help avoid unnecessary delays and surprises later on.

Quick Answer

Most ADU projects in the Greater Los Angeles area follow a similar path: property review, design, permit preparation, plan review, permit approval, and construction. While California provides statewide ADU regulations, local cities and agencies throughout Los Angeles County may have their own review procedures and requirements. Planning and permitting often take several months before construction begins.

Step 1: Review the Property

Before investing in plans, it’s important to understand what may be allowed on the property. This initial review helps identify opportunities, limitations, and potential challenges early in the process.

Items commonly reviewed include:

• Property size and configuration
• Existing structures
• Access requirements
• Utility connections
• Site conditions
• Applicable zoning regulations
• Local city requirements

Taking the time to evaluate the property upfront can help establish realistic project goals and identify requirements before moving into design.

Step 2: Develop the Design

Once the project goals are established, the design phase begins.

During this stage, homeowners work through decisions such as:

• ADU size
• Floor plan layout
• Bedroom and bathroom count
• Exterior appearance
• Location on the property
• Functional needs and priorities

The goal is to create a design that meets the homeowner’s needs while remaining compliant with California ADU regulations and local requirements within the Greater Los Angeles area.

Step 3: Prepare Plans for Submission

After the design is approved, detailed plans are prepared for permit review.

Depending on the project, this may include:

• Architectural drawings
• Structural engineering
• Site plans
• Energy calculations
• Additional supporting documentation

These plans become the official construction documents submitted to the appropriate city or county agency for review.

Step 4: Submit for Plan Review

Once the plans are complete, they are submitted to the appropriate city or county department for review.

Throughout the Greater Los Angeles area, this process may involve cities such as Los Angeles, Pasadena, Glendale, Burbank, Long Beach, Santa Clarita, and many others, each with its own review procedures.

During this process, agencies verify that the project complies with applicable building codes, California ADU regulations, and local requirements.

Depending on the jurisdiction and project scope, multiple departments may review the plans before approval can be granted.

Step 5: Respond to Plan Check Comments

Many projects receive comments during the review process.

These comments may relate to:

• Building code requirements
• Structural details
• Site conditions
• Energy compliance
• Project-specific requirements

Receiving comments is a normal part of the permitting process and does not necessarily indicate a problem with the project. In most cases, revisions are made and resubmitted for further review.

Why ADU Permitting Timelines Vary

Homeowners are often surprised to learn that two similar ADU projects can have very different permitting timelines.

Factors that may influence review times include:

• Agency workload
• Site-specific conditions
• Utility coordination requirements
• Plan revisions
• Project complexity
• Additional review requirements
• Differences between local jurisdictions

While California ADU laws have streamlined many aspects of the approval process, timelines can still vary significantly between cities throughout the Greater Los Angeles region.

Step 6: Obtain Permit Approval

Once all required reviews are completed and approvals are received, permits can be issued.

Permit issuance marks the transition from planning and permitting into active construction.

Construction should not begin until the required permits have been approved and issued.

Step 7: Begin Construction

After permits are issued, construction can move forward.

While every project is different, construction typically includes:

• Site preparation
• Foundations
• Framing
• Roofing and exterior finishes
• Mechanical, electrical, and plumbing work
• Insulation and drywall
• Interior finishes
• Final inspections

Construction timelines vary based on project size, site conditions, and overall complexity.

Common Factors That May Affect Timelines

Project schedules can vary due to several factors, including:

• Property conditions
• Utility requirements
• Agency review times
• Plan revisions
• Material lead times
• Changes made during the design process
• Local jurisdiction requirements

Planning ahead and making key decisions early can help keep a project moving forward more efficiently.

Frequently Asked Questions

How long does the ADU process take?

Timelines vary depending on the project and reviewing agency. While some projects move through the process more quickly, many require several months for planning, permitting, and approvals before construction begins. Review times can vary between cities throughout the Greater Los Angeles area.

Do I need permits for an ADU?

Yes. ADUs generally require permits and approvals before construction can begin.

Can construction start before permits are issued?

No. Construction should begin only after the required permits have been approved and issued.

What is the first step in building an ADU?

The first step is reviewing the property to determine what may be allowed based on California ADU regulations, local requirements, site conditions, and project goals.

Do all ADU projects require engineering?

Most ADU projects require structural engineering and other supporting documentation as part of the permit process.

Final Thoughts

Every ADU project is different, but understanding the process early can help homeowners make informed decisions and avoid unnecessary delays. From the initial property review through permitting and construction, proper planning plays an important role in creating a smoother project experience.

While California ADU laws provide the foundation for many projects, local requirements and review procedures can vary throughout the Greater Los Angeles area. Working with professionals who understand both state regulations and local permitting processes can help streamline the experience.

At AV Builders, we help homeowners throughout the Greater Los Angeles area navigate the entire process—from planning and design to permitting and construction—so projects can move forward with confidence and clarity.