How the ADU Plan Check Process Works in Los Angeles (2026 Guide)
one of the adus in the adu store.
Accessory Dwelling Units (ADUs) continue to be one of the most requested project types in Los Angeles. Whether you’re adding rental income, housing family members, or increasing long-term property value, ADUs offer flexibility that traditional additions often don’t.
However, many ADU projects slow down during plan check because the review process is more detailed than most homeowners expect. Even designers submitting their first ADU in LA are often surprised by the number of technical comments that come back from LADBS.
Based on experience navigating ADU projects in Los Angeles, here’s a clear breakdown of how the plan check process typically works — and where delays most commonly occur.
Step 1: Zoning & Feasibility (Before Design Begins)
Before any drawings are prepared, zoning feasibility should be confirmed.
For ADUs in Los Angeles, this typically includes:
Verifying lot eligibility
Reviewing overlays (Hillside, HPOZ, Specific Plans, etc.)
Confirming allowable square footage
Understanding height limits
Reviewing setback requirements
Confirming parking exemptions
Many homeowners assume a detached ADU automatically qualifies for the maximum square footage allowed by state law. In practice, site configuration, fire access, slope conditions, and utility placement often influence what is realistically feasible.
In my experience, early feasibility review is one of the most important steps in preventing later plan check revisions.
Step 2: Preparing the ADU Plan Set
Once feasibility is confirmed, the design and technical drawings are prepared for submittal.
A typical ADU plan set in Los Angeles includes:
Site plan
Floor plans
Elevations
Building sections
Structural notes and details
Title 24 energy documentation
Drainage or grading information (if applicable)
Green building notes
This is where coordination becomes critical.
Many first-round plan check comments stem from incomplete coordination between architectural drawings, structural details, and energy compliance documents.
Common Oversights in ADU Submittals
Some issues that frequently generate corrections include:
Egress window sizing not clearly dimensioned
Height calculations not aligned with LADBS measurement method
Foundation details inconsistent with structural notes
Energy forms not matching plan layouts
Missing smoke and carbon monoxide detector locations
Incomplete fire separation details between main house and ADU
These are not unusual mistakes — they are simply areas that reviewers consistently verify.
Careful cross-checking before submittal can significantly reduce correction cycles.
Step 3: LADBS Plan Check Review
may also route through additional departments such as grading or utilities.
The review process typically includes:
Initial plan check review
Issuance of correction comments
Resubmittal with written responses
Secondary review
Final approval (once all comments are cleared)
Correction comments are a normal part of the process. Almost every ADU project receives at least one round of comments.
Typical ADU Corrections Seen in Los Angeles
Based on experience, common correction themes include:
Egress window compliance
Stair geometry and handrail details
Smoke and CO detector placement
Fire separation and wall ratings
Structural anchorage details
Height measurement clarifications
Energy compliance coordination
The key is not to view corrections as failures, but as part of the regulatory review system.
Clear, organized responses — referencing sheet numbers and providing revised details — generally move projects forward more efficiently than defensive or vague replies.
Step 4: Approval & Permit Issuance
Once all comments are cleared, the project proceeds toward approval and permit issuance.
Depending on the site, additional clearances may be required for:
Grading (especially hillside properties)
Sewer or utility connections
Public works review
Only after all departments clear the project can the building permit be issued.
Many homeowners are surprised that “approval” and “permit issuance” are separate milestones. Understanding this distinction helps set realistic expectations for construction timelines.
How to Reduce ADU Plan Check Delays
While no project is guaranteed to pass on the first review, several practical steps can reduce avoidable delays:
Confirm zoning feasibility before investing heavily in design
Coordinate structural and energy documentation early
Double-check height calculations and measurement references
Ensure all life safety components are clearly shown on plans
Cross-reference structural notes with foundation details
Respond to correction comments clearly and respectfully
Avoid leaving items “to be clarified later”
Plan check is highly detail-oriented. Clarity and coordination often matter more than complexity.
Final Thoughts
ADUs remain one of the most impactful residential project types in Los Angeles, but navigating the plan check process requires attention to detail and coordination across multiple disciplines.
Whether you are a homeowner exploring your first ADU or a designer submitting to LADBS for the first time, understanding how the review process unfolds can help prevent unnecessary delays and stress.
If you are planning an ADU project in Los Angeles and want guidance from feasibility through plan check coordination, FO Studio assists with design development and permitting strategy.
Disclaimer
This article reflects personal experience navigating ADU projects and plan check in Los Angeles and is intended for educational purposes only. Always consult a licensed professional for project-specific code interpretation and compliance requirements.
