Do you need a Coastal Development Permit to build an ADU in Santa Monica?

If the property is in the California Coastal Zone, building an ADU can require a Coastal Development Permit in addition to the city ADU permit. Because Santa Monica does not yet have a certified Local Coastal Program, the California Coastal Commission — not the city — currently issues that coastal permit, which adds a step beyond the normal ministerial ADU process.

How did AB 462 change coastal ADU permitting?

AB 462, signed in October 2025 and effective immediately, requires the coastal permit review for an ADU to run at the same time as the local ADU permit instead of as a separate, later step, sets a 60-day decision deadline (after which the ADU can be deemed approved), and removes the ability to appeal an ADU coastal permit to the Coastal Commission where a city issues it under a certified Local Coastal Program.

Does owner-occupancy apply to ADUs in Santa Monica?

No, not for standard ADUs. California law (AB 976) permanently bars cities from requiring owner-occupancy for standard ADUs, and that applies in Santa Monica. Junior ADUs (JADUs) are the exception and still require the owner to live on the property.

ADU Rules in Santa Monica (Coastal Zone)

An ADU in Santa Monica is an Accessory Dwelling Unit governed by California state ADU law, with an extra Coastal Development Permit step for properties in the California Coastal Zone.

Santa Monica sits almost entirely within the Coastal Zone, so the coastal-permit process is the main thing that sets it apart from inland LA County cities.

The state baseline still applies

Everything in the Los Angeles County ADU baseline applies in Santa Monica: ministerial approval, no owner-occupancy requirement for standard ADUs, state size and setback minimums, and the impact-fee exemption under 750 sq ft. What's different is the coastal overlay.

The Coastal Development Permit step

Most of Santa Monica lies in the California Coastal Zone, where building an ADU can require a Coastal Development Permit (CDP) on top of the city ADU permit. Who issues that CDP depends on whether the city has a certified Local Coastal Program (LCP):

Santa Monica does not yet have a certified LCP. Its Land Use Plan exists, but the implementation half was never certified — so the California Coastal Commission, not the city, currently holds coastal-permit authority. In practice that means a two-step path: city approval plus a separate Commission permit.
The city authorized a renewed LCP process in 2026, aiming to certify a full LCP by roughly the end of 2027. Until then, expect the Coastal Commission to stay in the loop. (Timelines like this commonly slip — confirm the current status before you apply.)

What AB 462 changed in 2025

AB 462 (signed October 2025, effective immediately) streamlined coastal ADU permitting statewide:

The coastal-permit review must run concurrently with the local ADU permit — not as a separate, later process.
A complete coastal-permit application for an ADU must be decided within 60 days, or the ADU can be deemed approved.
Where a city issues the CDP under a certified LCP, that ADU coastal permit can no longer be appealed to the Coastal Commission.
After a declared disaster, a detached ADU can receive a certificate of occupancy before the main house is rebuilt — relevant to LA County wildfire recovery.

See the LA County ADU overview, learn how to rent out your ADU, or browse ADU rentals.

Frequently asked questions

Do you need a Coastal Development Permit to build an ADU in Santa Monica?: If the property is in the California Coastal Zone, building an ADU can require a Coastal Development Permit in addition to the city ADU permit. Because Santa Monica does not yet have a certified Local Coastal Program, the California Coastal Commission — not the city — currently issues that coastal permit, which adds a step beyond the normal ministerial ADU process.
How did AB 462 change coastal ADU permitting?: AB 462, signed in October 2025 and effective immediately, requires the coastal permit review for an ADU to run at the same time as the local ADU permit instead of as a separate, later step, sets a 60-day decision deadline (after which the ADU can be deemed approved), and removes the ability to appeal an ADU coastal permit to the Coastal Commission where a city issues it under a certified Local Coastal Program.
Does owner-occupancy apply to ADUs in Santa Monica?: No, not for standard ADUs. California law (AB 976) permanently bars cities from requiring owner-occupancy for standard ADUs, and that applies in Santa Monica. Junior ADUs (JADUs) are the exception and still require the owner to live on the property.

This guide is general information, not legal advice. Coastal-zone and ADU rules change and Santa Monica's coastal-permit authority is in transition; confirm current requirements with the City of Santa Monica and the California Coastal Commission before building.