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ADU Permits And Timeline

Last updated November 3, 2026

California law gives a city or county 15 business days to tell you in writing whether your ADU application is complete, then 60 days from a complete application to approve or deny it when a home already stands on the lot (Government Code section 66317). State law does not set how long design or construction takes.

The Review Deadlines In State Law

These come from the HCD ADU Handbook (March 2026) and the cited Government Code sections.

• Completeness check. The permitting agency must tell you in writing within 15 business days whether your application is complete. If it is not, it must list what is missing and how to fix it (Government Code section 66317).
• Approve or deny. If there is already a single-family or multifamily home on the lot, the agency must approve or deny a complete application within 60 days.
• Written reasons for a denial. A denial must come with a full set of comments listing what is defective and how to fix it, within the same 60 days.
• Appeals. If an application is found incomplete or is denied, the agency must offer an appeal process, with a written decision within 60 business days of the appeal.
• Coastal zone. A coastal development permit for an ADU must be approved or denied within 60 days of a complete application (Government Code section 66329).

A new house and an ADU submitted together can be reviewed together. The ADU application is considered without discretionary review or a hearing.

Typical Steps

1. Feasibility. Confirm zoning, lot size, setbacks, utilities, and any special area rules.
2. Design. A designer or architect draws site and floor plans. Some cities publish ready-made plans you can start from.
3. Submit. File plans, forms, and fees with the planning and building departments.
4. Corrections. Reviewers send comments. Answer them quickly and completely.
5. Permit issued. Pay remaining fees and begin work.
6. Inspections. The city inspects foundation, framing, plumbing, electrical, and final.
7. Certificate of occupancy. Required before anyone moves in.

Pre-Approved Plans

State law required each local agency to set up a program to pre-approve ADU plans by January 1, 2025, and to post the approved plans on its website (Government Code section 65852.27). Using a pre-approved plan can shorten plan review, but your site still needs its own review. Examples are in our city guides, such as Los Angeles and Sacramento.

What Varies And Why

• Design time, which depends on how custom the plans are and how fast you decide.
• Corrections from the city, which can add rounds of review.
• Utility company work, which has its own schedule.
• Contractor availability, material lead times, and weather.

Ask each builder for a written schedule with start and finish dates for each phase, and for what happens if the schedule slips. See Questions To Ask An ADU Builder.

Help When A City Is Not Following The Law

The handbook says to work with the permitting agency first. HCD offers technical assistance after an application is submitted, through the portal on its HCD ADU page.

Related guides: California ADU Rules, ADU Cost In California.