How does the ADU permit process work?

The California ADU permit process is ministerial — meaning there is no public hearing or discretionary design review as long as your project meets the zoning standards. In broad strokes, you assemble a complete plan set, submit it to the building department, pass a completeness check, go through plan review, respond to any corrections, get the permit, and then build with inspections at each stage.

The major steps, in order

1. Design and document preparation. You (or your design team) produce the architectural plans, structural plans, MEP plans, and a registered Title 24 CF1R energy report. These must all be coordinated with one another.
2. Submittal and completeness review. You submit the package — increasingly through an electronic portal such as ePlanLA or eTRACKiT. Under recent state law, the city has a short window (a 15-business-day completeness review under SB 543, effective January 1, 2026) to tell you whether anything is missing.
3. Plan check. Once deemed complete, a plan reviewer evaluates each discipline against the applicable codes. California's 60-day rule requires the agency to approve or deny a complete ADU application within 60 calendar days.
4. Corrections and resubmittal. If the reviewer has comments, you receive a written correction list. You revise and resubmit. This is normal and not a rejection.
5. Permit issuance. After plan check clears and fees are paid, the permit is issued and construction can begin.
6. Inspections. Inspectors verify the work against the approved plans at rough-in (before walls close) and at final, signing off toward a certificate of occupancy.

The legal protections that speed things up

California has stacked the deck in favor of ADU applicants. The 60-day rule (Government Code sections 66317 and 66320) means a complete application that the city fails to act on is deemed approved by operation of law. Cities must also maintain pre-approved plan programs under AB 1332, and projects using pre-approved plans must be decided within 30 days. These are legal mandates, not courtesies.

Where MEP and Title 24 fit

MEP plans and the Title 24 CF1R are part of the submittal package, and they are the documents most likely to generate corrections if they are incomplete or inconsistent with each other. Submitting coordinated, permit-ready MEP plans alongside a registered CF1R is the single biggest lever you have to pass the completeness check and clear plan review on the first pass.

The most important factor in your timeline is application completeness. A complete submittal enters plan check immediately and starts the 60-day clock; a missing document triggers an incomplete notice and resets the process.

For a full walkthrough including documents and fees, see our California ADU Permit Guide and How It Works. Requirements vary by jurisdiction — confirm the specifics with your local building department.