Can I Build an ADU in the California Coastal Zone?

This is the question beach-city homeowners ask after they hear that “the state already legalized ADUs, so the coast should be easy.” The coast is buildable. It is also a second permit system. The page below is the sequence a homeowner can actually walk: find out whether the lot is in the zone, find out who issues the coastal permit, keep the dates, and know what an appeal can still do. It is general information about the statutes and the public handouts checked on November 3, 2026. Your planner, and a licensed designer you hire, still read the lot.

First, find out whether the lot is in the zone

The coastal zone is a mapped strip, not “anywhere you can smell the ocean.” Public Resources Code section 30103 defines it as the land and water from Oregon to Mexico shown on the maps adopted with the Coastal Act. Inland, it is generally 1,000 yards from the mean high tide line. In significant estuarine, habitat, and recreational areas it runs to the first major ridgeline or five miles, whichever is less. In developed urban areas it is often less than 1,000 yards. San Francisco Bay is outside this zone. The Bay Conservation and Development Commission covers the Bay.

The official landward line is the set of 1:24,000 maps the Coastal Commission adopted. The Coastal Zone Boundary viewer is a digital copy of that line. The Commission’s own page says the digital file has not been adopted as the official boundary, is not survey-accurate, and can still leave you needing a formal boundary determination. Use it to get oriented. Then take the address and the assessor’s parcel number to the city planning counter. If the line cuts through the lot, ask the city’s coastal planner, or the Commission’s mapping staff, for a determination before you spend money on drawings.

A city map can be more useful than the statewide viewer because it also shows who permits that parcel. Newport Beach posts a Coastal Zone address search. San Diego’s Coastal Overlay is called out in Information Bulletin 400. Santa Barbara calls its coastal zone the S-D-3 overlay. Huntington Beach and Long Beach both tell you, on their ADU pages, to check the coastal zone before you assume a regular building permit is the only approval.

Two rulebooks apply at the same time

State ADU law starts at Government Code section 66310. The Legislature’s findings there call ADUs a needed form of housing in single-family and multifamily neighborhoods. The approval rules that follow, in sections 66314 through 66332, require ministerial review: if the project meets the objective standards, staff approves it without a discretionary hearing.

The building-permit side of that review is section 66317. The city has 15 business days to say in writing whether the ADU application is complete. A missed notice means the application is deemed complete. When a house or a multifamily building is already on the lot, the city then has 60 days to approve or deny. A missed decision means that ADU application is deemed approved. A denial has to list the defects and how to fix them. Our SB 543 timeline walks through those two clocks. They are the ADU permit. They are not, by themselves, the coastal permit.

Public Resources Code section 30600 says that, in addition to every other permit, a person who undertakes development in the coastal zone needs a coastal development permit, unless a listed exception applies. “Development” is broad. A new backyard cottage is development. So is a garage conversion that adds living space. Section 30610 lists exemptions, including some improvements to an existing single-family house, and it also lets the Commission exclude categories of development that it finds will not harm coastal resources. Whether your ADU fits one of those boxes is a city-and-Commission question. Do not assume a garage conversion is exempt because a neighbor’s inland project was.

Government Code section 66329, as amended by AB 462, is the hinge. Nothing in the ADU approval article supersedes or lessens the Coastal Act, except that the local government must, under section 66317, approve or deny a coastal development permit for an accessory dwelling within 60 days of a completed application, and it is not required to hold a public hearing. The coastal review runs at the same time as the ADU review.

HCD’s March 2026 ADU Handbook puts the same point in planning language: ADU law applies inside the coastal zone, and it does not lessen Coastal Act resource-protection policies. The handbook tells coastal cities to update their local coastal programs so housing rules and coastal rules can be applied together. It also says a local coastal program can require additional setbacks. On a bluff, next to a wetland, or in a public view corridor, the planner can still require a change. Ask which objective coastal standard they are using, and ask them to put it in the incomplete notice or the denial letter. A vague “it doesn’t fit the neighborhood” comment is not that standard.

Who actually issues the coastal permit

After a city or county gets a certified local coastal program, Public Resources Code section 30519 hands most new-development review to that local government. The Commission keeps permit authority over tidelands, submerged lands, and public trust lands, whether filled or not, and over ports and state universities in the coastal zone. A lot on the sand side of the bulkhead can be a Commission permit even when the house behind it is a city permit.

The Commission’s July 1, 2026 guidance on local coastal program amendments for ADUs, required by SB 1077 and linked from HCD’s ADU resources page, says about 90 percent of coastal-zone land is under a certified local coastal program. It names twelve jurisdictions that were still uncertified: Fortuna, the City of Monterey, Goleta, the City of Los Angeles, Hermosa Beach, Santa Monica, Torrance, Seal Beach, Costa Mesa, Aliso Viejo, San Clemente, and Solana Beach. In those places, plus deferred-certification pockets and the Commission’s retained-jurisdiction land, the Commission issues the coastal development permit.

Huntington Beach, Newport Beach, Long Beach, San Diego, and the City of Santa Barbara are not on that uncertified list. Goleta is. A Seal Beach or Costa Mesa homeowner should expect the Commission to be the coastal permitting agency. A Huntington Beach or Newport Beach homeowner should expect the city to be the permitting agency, and should still ask whether any part of the lot is tidelands, public trust land, or a deferred-certification area. Newport Beach’s coastal development permit instructions, revised October 3, 2023, say exactly that: the Commission is the review authority on tidelands, submerged lands, public trust lands, and deferred certification areas shown on the city’s post-certification map.

Section 66329(b) is the rule when the local government has no certified local coastal plan or program, as defined in Public Resources Code section 31001. The Commission must approve or deny the ADU coastal application within 60 days of receiving a completed one. The city must immediately tell the Commission that the ADU application is complete under section 66317. The Commission’s review runs alongside the city’s ADU review once the Commission has a completed coastal application under Government Code section 65943. If the ADU coastal permit is submitted together with a coastal permit for a new single-family or multifamily dwelling on the lot, the Commission may wait to decide the ADU until it decides the new house. In every other case, if the Commission has not approved or denied the completed ADU coastal application within 60 days, section 66329(b)(5) says the application is deemed approved.

Read that deemed-approved sentence carefully. It is written for the Coastal Commission. Section 66329(a), the rule for a city that does have a certified local coastal program, requires the city to approve or deny within 60 days and to run that review at the same time as the ADU permit. It does not say the city’s coastal permit is deemed approved if the city is late. The ADU application itself can still be deemed approved under section 66317 when a house is already on the lot and the city misses the 60-day ADU decision. Those are two applications. Keep both receipt dates.

HCD’s handbook describes the local 60-day coastal clock as applying when there is an existing primary dwelling, because section 66329(a) points at section 66317. Section 66317 lets the city wait on an ADU that is filed with a permit for a new house. If you are building the ADU at the same time as a new house, ask in writing whether either clock is paused until the new house is decided.

What an appeal can still do

Public Resources Code section 30603 is the Coastal Act appeal. After a local coastal program is certified, a local coastal approval can be appealed to the Commission only for certain locations: between the sea and the first public road, or within 300 feet of a beach or the mean high tide line; on tidelands or public trust lands; within 100 feet of a wetland, estuary, or stream; within 300 feet of a coastal bluff; and a few other categories. The grounds are narrow. The appeal has to allege that the project does not conform to the certified local coastal program or to the Coastal Act’s public-access policies. The local action otherwise becomes final at the close of business on the 10th working day after the Commission receives notice, unless an appeal is filed in that window.

AB 462 added section 66329(c). Any decision of a local government under section 66329(a) is not subject to appeal under section 30603. A neighbor who does not like a city’s approval of your ADU coastal permit cannot take that decision to the Coastal Commission on the 30603 path. The July 1, 2026 Commission guidance describes this as making local coastal permits for ADU-only and junior-ADU-only projects no longer appealable to the Commission, and it describes the bill as shortening an earlier 90-day coastal deadline to 60 days for ADU-only, junior-ADU-only, and combined ADU-and-junior projects.

The chaptered bill itself amends sections 66328 and 66329. Those sections sit in the accessory dwelling unit article. Section 66329 uses “accessory dwelling” and “accessory dwelling unit.” It does not use the words “junior accessory dwelling unit.” If the only unit you are adding is a junior ADU, show the counter both the statute and the Commission’s July 1, 2026 reading, and ask which one the city is applying.

Three limits stay in place. The 30603 bar is about a local government’s decision under subdivision (a). When the Commission is the permitting agency, there is no Commission appeal of that kind, because the Commission is the decision-maker. A city finding that your ADU application is incomplete, or a denial, still has the local appeal in section 66317(d): a final written decision within 60 business days after the agency receives your written appeal. And section 66329(c) does not say anything about a lawsuit in court. This page is not a prediction of how a judge would treat a particular lot.

The Commission’s guidance also says the Coastal Act’s resource rules still apply while the procedures got shorter. Public access, habitat, wetlands, and hazards such as bluff retreat, flooding, and sea-level rise remain part of the review. A faster clock is not a waiver of those policies.

If a disaster damaged the main house

The usual rule is in Government Code section 66328(a). The city cannot issue a certificate of occupancy for the ADU before it issues one for the primary dwelling.

AB 462 added a narrow exception, and it has been in effect since October 10, 2025. The city must issue the ADU’s certificate of occupancy even if the primary dwelling does not have one yet, when all of the following are true:

• The ADU is in a county that is under a proclamation of a state of emergency made by the Governor on or after February 1, 2025.
• The primary dwelling was substantially damaged or destroyed by an event named in that proclamation.
• The ADU has been issued its construction permits and has passed all required inspections.

Section 66328(c) says this exception does not apply to an ADU attached to the primary dwelling. A detached cottage that is fully permitted and fully inspected can get its certificate of occupancy while the main house is still being rebuilt. An attached unit cannot, under this statute. The exception is a certificate of occupancy. It does not skip the coastal permit, the building permit, or the inspections. It also does not cover every local emergency declaration. The proclamation has to be the Governor’s, dated on or after February 1, 2025, and the damage has to be from the event that proclamation names. HCD’s March 2026 handbook restates those limits and points readers back to section 66328.

What to do, in order

1. Check the line, then confirm it. Open the Coastal Zone Boundary viewer. Write down whether the parcel looks inside, outside, or crossed by the line. Take that, plus the parcel number, to the planning counter. In Newport Beach, run the city address search first.
2. Ask which permit you need. The answer is one of four: no coastal permit because the project is exempt or excluded; a city coastal development permit; a Commission coastal development permit; or a city building permit plus a separate coastal step the city has given its own name. Get the name of the application in writing.
3. Submit a package the counter can stamp complete. Site plan, floor plan, elevations, the coastal supplemental form if the city has one, and photos of the existing house. A missing sheet starts the completeness clock over. It does not start a 60-day approval.
4. Save the dates. You want the day the city received the ADU application, the day it said that application was complete, and the day it received the coastal application. The 15-business-day notice and the 60-day decision are counted from different events. Business days in section 66317 exclude Saturdays, Sundays, and state holidays. The 60-day coastal deadline in section 66329 is not written as “business days.”
5. Ask about a hearing before you calendar one. Section 66329 says the local government is not required to hold a public hearing on an ADU coastal development permit. Some city handouts still describe a hearing. If the counter schedules one, ask which code section requires it for an ADU.
6. If a deadline passes, write a short letter. For the ADU application, a missed 15-business-day notice means it is deemed complete, and a missed 60-day decision means it is deemed approved when a house is already on the lot. For a city coastal permit, ask for the decision the statute requires and cite section 66329(a). For a Commission coastal permit, cite section 66329(b)(5) if you are outside the new-house exception. HCD’s ADU team reviews local ADU ordinances and permitting practices. Commission process questions go to the district office for that stretch of coast.

What to ask at the planning counter

Print this list. The useful answer is the one a planner will initial or email back.

1. Is this parcel inside the coastal zone? Does the boundary cross it?
2. Is any part of it in the Commission’s retained jurisdiction, meaning tidelands, submerged lands, or public trust lands, or in an area of deferred certification?
3. Does this ADU need a coastal development permit, or is it exempt or excluded under your certified local coastal program? If you have a categorical exclusion order, does this lot and this unit type fall inside it?
4. Who issues that permit, the city or the Coastal Commission?
5. What date will you treat each application as complete, and will you approve or deny the coastal permit within 60 days of that date, at the same time as the ADU permit?
6. Are you holding a public hearing? Section 66329 says you are not required to.
7. If you approve a city coastal permit, do you treat that decision as not appealable to the Coastal Commission under Public Resources Code section 30603?
8. Which coastal standards will you apply on this lot: bluff or shoreline setback, habitat or wetland buffer, public access, public views, flood, or parking? Please name the local coastal program policy.
9. If this county is under a Governor’s emergency proclamation issued on or after February 1, 2025, and the main house was substantially damaged by that event, can a detached ADU get a certificate of occupancy before the main house does, once it has passed inspection?

Also ask for the fee sheet. This page does not print a coastal-permit fee, a plan-check fee, or a school fee, because those numbers are local and they change. A construction range in our cost guide is a planning estimate for the building contract. It is not a city fee.

Rentals have their own rule, separate from the coastal permit. HCD’s March 2026 handbook says units created under Government Code section 66323, and junior ADUs, must be rented for terms longer than 30 days, citing sections 66323(e) and 66333(g). A coastal city can have additional short-term-rental rules in its local coastal program. Ask before you underwrite the project as a nightly rental. Other statute changes, including bills that take effect January 1, 2027, are on the 2026 law update.

What the beach-city pages say right now

Checked November 3, 2026. City pages move slower than the statute. Use them to learn the local form, then compare the clock and the hearing rule to section 66329.

Huntington Beach

The city’s Accessory Dwelling Units page says it ministerially reviews ADUs and junior ADUs, and that development in the coastal zone may require a coastal development permit. It points you to a city handout for the standards. The page does not restate the 60-day coastal clock. Questions listed on that page go to (714) 536-5511. Lot-level Huntington Beach steps are in the Huntington Beach guide.

Newport Beach

The city’s ADU permit page says a coastal-zone property may need a coastal development permit before plan check, and that the permit could possibly require a hearing. The address search linked above is the city’s tool for whether the parcel is in the zone. The October 3, 2023 coastal-permit instructions say a permit is required for development in the zone unless it is exempt or excluded, and they list the findings the review authority has to make, including consistency with the certified local coastal program. Section 66329, in effect since October 10, 2025, says the city is not required to hold a public hearing. Ask the counter which instruction it is following. The Newport Beach guide covers the city’s size caps and the fees that page actually prints.

Long Beach

The city’s Accessory Dwelling Units page says Long Beach is applying state ADU law directly while a local ordinance is still being written. A property in the coastal zone must get an administrative, no-hearing local coastal development permit before the building-permit application. Coastal-zone projects are not eligible for over-the-counter review. Planning questions on that page go to 562.570.6194. The Long Beach guide follows the rest of that submittal, including the in-person USB requirement.

San Diego

Information Bulletin 400 (January 2026) says a coastal development permit is required for an ADU or junior ADU in the Coastal Overlay Zone that is not completely inside the existing primary structure, that adds habitable area, or that converts non-habitable space. Some junior ADUs can be exempt under the municipal code section the bulletin cites. The bulletin says the city’s decision on a coastal development permit application for an ADU is not appealable to the Coastal Commission. It also warns that several later ordinances are not effective in the Coastal Overlay until the Commission certifies them. The San Diego guide stays with that bulletin. This page is the statewide clock.

Santa Barbara

The city’s ADU project guidance page says that on April 6, 2022 the Coastal Commission determined the city’s ADU ordinance is legally adequate and effective in the coastal zone. The planning counter on that page is (805) 564-5578. The city’s Coastal Zone Review supplemental application, as posted when this page was reviewed, still describes three levels: exemption, exclusion, and coastal development permit. The single-family improvement exemption on that form does not include a new detached accessory dwelling unit. Exemptions and exclusions are acted on by staff without a hearing. A coastal development permit on that form goes to the Staff Hearing Officer or the Planning Commission after a noticed public hearing. The form says to allow at least 30 calendar days for a determination, and that a coastal development permit may take 6 to 12 months or longer. That form does not mention section 66329. Ask the counter whether your unit is an exemption, and which clock and hearing rule they are using, before you plan around 6 to 12 months. The Santa Barbara guide is the city overview.

Questions homeowners ask

Can I build an ADU in the California coastal zone?

Yes. State ADU law applies in the coastal zone, and the Coastal Act still applies. If the project counts as development and no exemption or exclusion covers it, you also need a coastal development permit.

How long does a city have to decide an ADU coastal permit?

Government Code section 66329 requires approval or denial within 60 days of a completed application. A city with a certified local coastal program decides its own coastal permit and is not required to hold a public hearing. If the city has no certified local coastal program, the Coastal Commission has the same 60 days, and a missed deadline deems that Commission application approved, except when the ADU coastal permit is filed with a coastal permit for a new house.

Can someone appeal my city’s ADU coastal permit to the Coastal Commission?

A local decision under Government Code section 66329(a) is not subject to appeal under Public Resources Code section 30603. If the city calls the ADU application incomplete or denies it, you still have the separate local appeal in Government Code section 66317.

Can I live in the ADU before the main house is rebuilt after a disaster?

Only in a narrow case. The city must issue a certificate of occupancy for a detached ADU even if the main house does not have one yet when the county is under a Governor’s state-of-emergency proclamation issued on or after February 1, 2025, the main house was substantially damaged or destroyed by the event named in that proclamation, and the ADU has construction permits and has passed all required inspections. An ADU attached to the main house stays under the usual rule: no ADU certificate of occupancy before the main house has one.

Sources

Reviewed November 3, 2026. Statute text was read that day on leginfo.legislature.ca.gov. City and Commission pages were opened that day and returned a live page or file.

• AB 462, Chapter 491, Statutes of 2025. Approved and filed October 10, 2025. Urgency statute, effective that day. Amends Government Code sections 66328 and 66329.
• Government Code section 66329. Coastal development permit timing, concurrent review, Commission deemed-approval, and the section 30603 appeal limit. Amended by Stats. 2025, Ch. 491.
• Government Code section 66328. Certificate of occupancy, including the emergency exception for a detached ADU.
• Government Code section 66317. Ministerial ADU review, 15-business-day completeness notice, 60-day decision, deemed approval, and the local appeal.
• Government Code section 66310. Start of the ADU chapter.
• Public Resources Code section 30103. Coastal zone definition.
• Public Resources Code section 30600. Coastal development permit required for development in the zone, in addition to other permits.
• Public Resources Code section 30610. Developments and areas that do not require a coastal development permit.
• Public Resources Code section 30519. After certification, most review moves to the local government. Tidelands, submerged lands, and public trust lands stay with the Commission.
• Public Resources Code section 30603. Which local coastal approvals can be appealed to the Commission, and the 10-working-day window.
• HCD Accessory Dwelling Unit Handbook, March 2026 (PDF), linked from the ADU Handbook page. Coastal-zone questions, the section 66328 certificate-of-occupancy answer, and the rental-term citations.
• California Coastal Commission, Guidance on Processing Local Coastal Program Amendments for ADUs, July 1, 2026 (PDF), posted from the Commission’s SB 1077 page and linked by HCD. Uncertified-jurisdiction list, and the Commission’s description of the appeal change and the 60-day deadline.
• Coastal Commission, Coastal Zone Boundary viewer. Digital map, with the Commission’s limits on using it as a survey.
• Coastal Commission contact page. District offices.
• City of Huntington Beach, Accessory Dwelling Units. Ministerial review, and a coastal development permit where the zone requires one.
• City of Newport Beach, Coastal Zone address search.
• Newport Beach ADU permit page. Coastal permit may come before plan check, and the page still mentions a possible hearing.
• City of Newport Beach, Coastal Development Permit instructions, revised October 3, 2023.
• City of Long Beach, Accessory Dwelling Units. Administrative local coastal development permit before the building permit.
• City of San Diego, Information Bulletin 400, January 2026. When a coastal permit is required, and the city’s statement that an ADU coastal decision is not appealable to the Commission.
• City of Santa Barbara, ADU project guidance. April 6, 2022 Coastal Commission adequacy finding for the coastal ADU ordinance.
• City of Santa Barbara, Coastal Zone Review supplemental application (PDF). Exemption, exclusion, and coastal development permit paths, including the hearing and 6-to-12-month language on that form.

Related pages on this site: the legal requirements guide, the permit-clock explainer, and the planning guide.