Quick Answer: Two California bills — SB 543 and AB 462 — changed ADU rules effective 2026. SB 543 exempts ADUs under 500 sq ft from school fees, clarifies that you can build up to three ADU types on one lot, and caps permit intake at 15 business days. AB 462 gives coastal properties (like Oxnard) a 60-day CDP decision deadline and blocks Coastal Commission appeals on individual ADU projects. These laws make ADUs cheaper, faster, and legally clearer for Ventura County homeowners. Safeway Construction has built ADUs across Ventura County for 20+ years — CA Lic #1066117.
Two bills signed by Governor Newsom in 2025 changed the ADU rulebook for every California homeowner — and the changes took effect January 1, 2026. If you've been thinking about building an ADU in Simi Valley, Thousand Oaks, Camarillo, Moorpark, or Oxnard, these new laws directly affect your fees, your permitting timeline, and what you're allowed to build.
This isn't a general “what is an ADU” guide. We're focusing specifically on what changed in 2026, why it matters, and what it means for your project right now.
The two bills: SB 543 and AB 462. Here's what each one does.
SB 543: The Law That Cuts Fees and Clears Up the Rules
SB 543 took effect January 1, 2026. It addresses three things Ventura County homeowners have been running into for years: unclear size rules, surprise fees, and slow permit intake.
Fee Exemptions That Save Real Money
The most impactful change in SB 543 is the fee structure. Under prior law, ADUs could be subject to school impact fees and other developer fees that added thousands to project costs — regardless of how small the unit was. SB 543 changed that:
- ADUs and JADUs under 500 square feet of interior livable space are exempt from school fees entirely.
- ADUs under 750 square feet are exempt from most development impact fees.
- Because JADUs are capped at 500 square feet by definition, every JADU in California is now fully exempt from both school fees and development impact fees.
For Ventura County homeowners, this is significant. School developer fees in Simi Valley (charged by SVUSD) run $4.14 per square foot. A 750-square-foot ADU previously owed about $3,100 in school fees alone — now that's zero. Across all applicable fees, the savings on a small ADU can run $5,000 to $15,000.
Want to know what your specific ADU project would cost with the 2026 fee changes factored in? Get a free AI-powered estimate at SafewayQuickQuote.com — it takes about 2 minutes and gives you a real price range without a contractor visit.
Size Calculations Are Now Unambiguous
Before SB 543, there was genuine confusion about whether ADU size limits referred to interior livable space or total footprint (including walls, stairs, and exterior elements). SB 543 settles it: all ADU and JADU size limits refer to interior livable square footage. Walls, stairs, and exterior elements don't count against your square footage cap.
This means you can design to the actual 800-square-foot limit for a detached ADU without worrying that your exterior wall thickness is chewing into that number.
You Can Now Combine Multiple ADU Types on One Lot
This is the change that surprises most homeowners we talk to. SB 543 removes all ambiguity. A single-family lot can now legally have:
- One detached ADU (up to 800 sq ft, or up to 1,200 sq ft in some cases)
- One attached or converted ADU (converted from existing space like a basement or attached garage)
- One JADU (up to 500 sq ft, carved from within the primary dwelling)
That's three separate units on a single-family lot — in addition to the primary home. For homeowners in Simi Valley's larger lots or Thousand Oaks neighborhoods with detached garages, this opens up income-generating options that weren't previously clear under state law.
Faster Permit Intake — With Teeth
SB 543 fixes permit intake delays with clear deadlines:
- Cities must determine if an ADU application is complete within 15 business days of receipt.
- If the city fails to respond within 15 business days, the application is automatically deemed complete.
- If incomplete, the city must provide a specific list of missing items. It cannot raise new objections during resubmittal review.
- After resubmittal, the city has another 15 business days to respond.
In practical terms: the total intake phase is now capped at 30 business days maximum (about 6 weeks) even in the worst case.
AB 462: Coastal Zone ADUs Just Got Dramatically Easier
AB 462 was signed on October 10, 2025 and took effect immediately as an urgency measure. It applies to properties in the California Coastal Zone — in Ventura County, that includes oceanfront and near-coast properties in Oxnard (Channel Islands Harbor, Oxnard Shores, Hollywood Beach, Silverstrand Beach), parts of Port Hueneme, and portions of unincorporated coastal Ventura County.
The 60-Day CDP Decision Deadline
Before AB 462, coastal ADU projects were caught in a sequential review trap. AB 462 breaks that:
- Cities with a certified local coastal program must now run CDP review concurrently with ADU ministerial review, not after it.
- Cities must issue an approval or denial on a coastal ADU CDP within 60 days of receiving a complete application.
For Oxnard homeowners, projects that previously took 6–12 months just for permitting can now move through the coastal approval phase in 60 days.
No More Coastal Commission Appeals on Individual ADU Projects
Under prior law, anyone could appeal a locally-approved CDP for an ADU to the California Coastal Commission — delaying a project by 6–18 months. AB 462 eliminates that pathway for individual ADU projects. Decisions made at the local level stay at the local level. For homeowners near the Oxnard coast, that uncertainty is now gone.
Disaster Relief: ADUs Can Get Certificates of Occupancy Before the Main Home Is Rebuilt
If a primary home was substantially damaged in a state-declared emergency (on or after February 1, 2025), and the homeowner has a detached ADU that has passed inspections, the city must issue a certificate of occupancy for the ADU — even if the primary dwelling hasn't been rebuilt yet. This allows families to live in the ADU or rent it while the main home reconstruction is underway.
What This Means for Each Type of Ventura County Homeowner
Garage Conversion in Simi Valley or Moorpark
Garage conversions typically produce ADUs under 500 square feet — or can be designed to. Under SB 543, a sub-500-square-foot garage conversion ADU is now fully exempt from school fees and development impact fees. A Moorpark garage conversion that previously owed $4,000–$6,000 in fees may now owe significantly less.
Detached ADU + JADU Combination
SB 543's combination rule is now explicit. A Simi Valley homeowner can legally build a detached backyard ADU (up to 800 sq ft) AND convert a bedroom into a JADU (up to 500 sq ft). Two income streams:
- Detached ADU rental: $1,600–$2,200/month
- JADU rental: $900–$1,400/month
- Combined potential: $2,500–$3,600/month
Get a cost estimate for your specific lot at SafewayQuickQuote.com before finalizing your plans.
Coastal Property in Oxnard
AB 462 removed the two biggest obstacles: sequential permit review and Coastal Commission appeal risk. If you own property in Oxnard's coastal neighborhoods and have been holding off, those barriers are materially reduced. We can help coordinate the concurrent permit submission process.
How the 2026 Laws Fit With Prior ADU Legislation
SB 543 and AB 462 build on a series of ADU bills since 2020:
- AB 2221 and SB 897 (2022): Set the current 800-square-foot maximum for detached ADUs and reduced setback requirements.
- AB 976 (2023): Eliminated owner-occupancy requirements for ADUs (though not for JADUs).
- AB 2533 (2024): Created the ADU amnesty program for pre-1978 unpermitted units — see our guide on legalizing an unpermitted ADU in Ventura County.
- SB 9 (2022): Allowed lot splits on single-family lots, enabling more ADU development potential.
- SB 543 and AB 462 (2025, effective 2026): Reduced fees, clarified combination rules, sped up intake timelines, and streamlined coastal permitting.
Permit Process: What to Expect in Key Ventura County Cities
| City | Typical ADU Timeline | 2026 Changes |
|---|---|---|
| Simi Valley | 8–12 weeks | Intake capped at 15 business days. SVUSD school fees ($4.14/sq ft) waived for units under 500 sq ft. |
| Thousand Oaks | 10–14 weeks | CVUSD fee ($3.20/sq ft) waived for sub-500-sq-ft ADUs. 15-day intake deadline applies. |
| Moorpark | 10–14 weeks | MUSD fee exemption for sub-500-sq-ft units. Three-agency process benefits from intake deadline. |
| Oxnard (Coastal) | Previously 6–12 months | AB 462: 60-day CDP deadline. Concurrent review. No Coastal Commission appeals. |
| Camarillo | 8–12 weeks | State ADU standards apply. Fee exemptions under SB 543 apply city-wide. |
FAQ: California 2026 ADU Laws for Ventura County Homeowners
What does SB 543 change about ADU fees in California?
SB 543 exempts ADUs and JADUs under 500 sq ft from school impact fees. ADUs under 750 sq ft avoid most development impact fees. For Ventura County projects, the savings can range from $5,000 to $15,000 on smaller units.
Can I build more than one ADU on my single-family lot in Ventura County?
Yes. SB 543 explicitly allows one detached ADU, one attached or converted ADU, and one JADU simultaneously on a single-family lot. This is settled state law as of January 1, 2026.
How long does a city have to process my ADU permit application under the 2026 laws?
Under SB 543, cities must determine whether your application is complete within 15 business days. If they don't respond, the application is automatically deemed complete. After resubmittal, they have another 15 business days.
What does AB 462 mean for ADUs in Oxnard or other Ventura County coastal areas?
AB 462 requires cities with certified local coastal programs to approve or deny a Coastal Development Permit for an ADU within 60 days. The CDP review runs concurrently with ADU permit review. Appeals to the California Coastal Commission on individual ADU projects are no longer permitted.
Can a JADU be used as an Airbnb or short-term rental?
No. SB 543 prohibits JADUs from being used as short-term rentals. JADUs must be rented for terms longer than 30 days. This applies in Simi Valley, Thousand Oaks, Moorpark, Camarillo, Oxnard, and all California cities.
What happens if a city's ADU ordinance isn't submitted to HCD within 60 days?
The ordinance is automatically void under SB 543. The city defaults to the more permissive state ADU standards — which is generally favorable for homeowners trying to build.
How do the 2026 law changes affect my ADU's investment value in Ventura County?
Lower fees and faster permitting reduce your upfront cost and project risk. A detached ADU in Simi Valley or Thousand Oaks typically adds $150,000–$220,000 in property value and generates $1,600–$2,400 per month in rental income. The 2026 fee exemptions make compact ADUs (under 500 sq ft) and JADUs particularly cost-effective.
Ready to Start Your ADU Project?
The 2026 ADU laws create a better environment for Ventura County homeowners than existed 12 months ago — lower fees, faster intake, and legal clarity on what you can build. We've been building ADUs across Ventura County for over 20 years. Our clients in Simi Valley, Thousand Oaks, Moorpark, Camarillo, and Oxnard have given us a 5.0-star Google rating — and the projects to match.