Do ADUs in California's coastal zone need a coastal development permit?

They can. State ADU law applies in the coastal zone but does not override the California Coastal Act, so your ADU may need a coastal development permit (CDP) depending on its location and your local coastal program. Where a CDP is required, state law now sets a 60-day decision deadline and removes the requirement for a public hearing.

How state ADU law and the Coastal Act fit together

Government Code section 66329, amended by AB 462 effective October 10, 2025, says the ADU statutes do not supersede or lessen the Coastal Act, with specific exceptions:

• Cities and counties with a certified local coastal program (LCP) must approve or deny a CDP application for an ADU within 60 days of receiving a complete application, are not required to hold a public hearing, and must process the CDP at the same time as the ADU permit. Their decisions on these ADU CDPs are not appealable to the Coastal Commission under Public Resources Code section 30603.
• Areas without a certified LCP go to the Coastal Commission, which must approve or deny within 60 days of a complete application. The local agency must immediately notify the Commission when the ADU permit application is complete. If the Commission does not act within 60 days, the CDP application is deemed approved, except when the ADU CDP is filed together with a CDP for a new house, in which case the Commission may wait to decide the ADU until it decides the house.

Other coastal differences

• HCD notes that additional setbacks may be required in the coastal zone if the LCP requires them.
• Whether your particular ADU needs a full CDP or qualifies for an exemption or waiver depends on the LCP and your exact location, so ask your planning department early.
• For properties destroyed in the January 2025 Los Angeles fires, the Governor's January 16, 2025 executive order extended certain CEQA and Coastal Act exemptions to ADUs. Confirm what applies to your property.

What this means for your MEP plans and permit set

A CDP review focuses on coastal resources rather than wiring or piping, but some MEP decisions appear on the coastal site plan: new utility trenches, outdoor equipment pads, drainage and, on properties without sewer, the onsite wastewater system. Showing them consistently on the site plan, MEP sheets and CDP application avoids conflicting reviews. Because the CDP and the ADU permit run at the same time, submitting a complete MEP set and Title 24 report up front helps both reviews move. See the 60-day rule, ADU setbacks, and the California ADU permit guide. Confirm coastal requirements with your local planning department or the Coastal Commission district office.

Sources: leginfo.legislature.ca.gov, hcd.ca.gov, gov.ca.gov.