ADUs and SB 9 lot splits on burned lots in Altadena
After the January 2025 Eaton Fire, Altadena owners can add an ADU to a rebuild, and LA County defers ADU fees for eligible owner-occupants. SB 9 lot splits are suspended on lots inside the Eaton Fire boundary in Very High Fire Hazard Severity Zones. SB 1090 pauses new SB 1123 projects in 91001 and 91003 until 2030.
Quick answers
- •ADUs are allowed with a County rebuild. The County's fee deferral covers an ADU built with an owner-occupied rebuild.[1][2]
- •ADUs are common in Eaton rebuilds: about 1 in 3 County parcels with an issued Eaton building permit also has an issued ADU permit (32–34%, depending on how you count). [Estimate: our analysis][3]
- •A junior ADU (JADU) is up to 500 sq ft, inside the main home, with its own outside door.[4]
- •SB 9 lot splits and duplexes are suspended on lots that are both inside the Eaton Fire boundary and in a Very High Fire Hazard Severity Zone (mainly Altadena's eastern foothills). Elsewhere, SB 9 still applies.[5][6]
- •SB 1090 pauses fast-track SB 1123 small-lot projects in ZIPs 91001 and 91003 for applications filed on or after Oct 1, 2026, until Jan 1, 2030. It does not cover SB 9 or ADUs.[7][8]
Wondering if an ADU fits your lot and budget? We'll show you options in a free Rebuild Roadmap. [Owner to confirm]
(From the Altadena Rebuild Team, our sponsor)
Can I build an ADU on my burned lot in Altadena?
- •An ADU has its own kitchen and bathroom. It can be attached or detached.[4]
- •A JADU is up to 500 sq ft, inside the main home, with its own exterior entrance.[4]
- •The County's rebuild fee deferral covers an ADU built as part of an owner-occupied rebuild, and a standalone ADU that you live in for now.[2]
- •Self-certification can be used for a replacement ADU on eligible lots.[9]
- •An ADU built as part of rebuilding the main home is exempt from installing rooftop solar, but it must be solar-ready.[10]
- •ADU before the main house: the Governor's order EO N-9-25 lets an ADU on a lot destroyed or badly damaged in the Eaton Fire get its certificate of occupancy before the main home. That rule runs until Jan 16, 2028, unless ended sooner.[14]
- •ADU on an empty lot: in unincorporated Altadena, your household can live in a standalone ADU (no main house yet) until Jan 7, 2030. The ADU can stay when you rebuild the main home; just show it on the site plan.[14]
- •Prefab ADU: a 2025 state law (AB 818) requires local agencies to decide within 10 business days on permits for manufactured, modular, or detached ADUs placed on a lot while the home is rebuilt.[15]
- •The County publishes ADU/JADU guidance on its rebuild policies page.[4]
County vs. Pasadena
Building an ADU first so you can move home sooner? As an ADU builder in Altadena and Pasadena, we can show how phasing could work on your lot. [Owner to confirm]
Can I split my lot under SB 9 after the Eaton Fire?
What SB 9 normally does: it lets owners in single-family zones split a lot or build two homes with ministerial (staff-level) approval.[6]
What changed after the fires:
- •Executive Order N-32-25 (July 30, 2025) suspended those SB 9 rules in Very High Fire Hazard Severity Zones inside the Eaton and Palisades fire boundaries. The Governor's office said this covers the "eastern foothills portions of Altadena."[5]
- •LA County's June 8, 2026 SB 9 memo says a site covered by the order is not eligible for ministerial SB 9 review.[6]
- •Pasadena: in September 2025 the City Council took up an interim urgency ordinance to prohibit SB 9 applications in Very High Fire Hazard Severity Zones within the Eaton Fire boundary in the City.[12] [Verify adoption and current status with the City before publishing]
- •Outside those zones, SB 9 still applies.[5][6]
How to check your lot: look up your fire hazard zone on CAL FIRE's map and confirm with Regional Planning, (213) 974-6411.[1]
What does SB 1090 change in Altadena?
- •Signed Sept 30, 2026, and in effect since Oct 1, 2026.[7][8]
- •Removes ministerial approval for SB 1123 / Starter Home Revitalization Act projects in ZIPs 91001 and 91003 if the application was filed on or after Oct 1, 2026. Runs until Jan 1, 2030.[7]
- •Not covered: SB 9 lot splits and duplexes, ADUs. The bill's author says fully affordable projects keep an exception. [3rd-party: Altadena Now][13]
Free download: The Altadena Rebuild Checklist, with an "ADU or not?" decision box.
From the Altadena Rebuild Team
(Sponsored content)R&M Builders Inc (CSLB #1077165, B – General Building, verify) and our partner architect can price a home plus ADU together, under one fixed-price construction contract. [Owner to confirm]
Independent firms, separate contracts, no referral fees.
FAQ
See what fits your lot: home, ADU, or both.
Sources (checked Oct 22, 2026 unless noted)
- 1.LA County Recovers, Like-For-Like Rebuild:
- 2.LA County Recovers, Fee Deferrals & Refunds:
- 3.LA County EPIC-LA Eaton/Palisades cases (public ArcGIS layer), data pulled Oct 22, 2026: 867 of 2,529 parcels with an issued Eaton building permit (34%) have an issued permit whose description contains the word "ADU"; using the layer's ADU flag field instead gives 802 (32%). Building permits only (PermitManagement module), Altadena-area Eaton cases, issued through Oct 21, 2026[Estimate: our analysis]
- 4.LA County Recovers, Rebuild Policies, Interpretations and Exemptions (ADU/JADU section):
- 5.Office of the Governor, "Governor Newsom strengthens local control in Los Angeles burn scar areas" (July 30, 2025):
- 6.LA County Regional Planning, SB 9 memo (June 8, 2026):
- 7.SB 1090 (2026), enrolled text:State Board of Equalization 2026 enacted-legislation report (Ch. 1006):https://boe.ca.gov/meetings/pdf/2026/202610-LRSD-Rprt.pdf
*(read via CapitolTrack copy of the enrolled bill; leginfo blocked our checker)*
- 8.Supervisor Kathryn Barger, statement on SB 1090 (Sept 30, 2026):
- 9.LA County Recovers, Self-Certification:
- 10.LA County, EO N-29-25 Implementation sheet:
- 11.City of Pasadena, Fire Rebuild Fee Waiver and Refund Program:
- 12.City of Pasadena, Ordinance Fact Sheet, SB 9 – Very High Fire Hazard Severity Zones (Sept 8, 2025):
- 13.Altadena Now, "Pérez: Altadena Density Pause Covers Only SB 1123 Projects…"[3rd-party]
- 14.LA County Regional Planning, Zoning Interpretation No. 2025-04, Occupancy Time Limit for Standalone ADUs (Apr 23, 2025; describes EO N-9-25) (checked Oct 23, 2026):
*(search snapshot)*
- 15.LA County Recovers, New Laws (AB 818) (checked Oct 23, 2026):
*(search snapshot)*
- 16.City of Pasadena, Information on Rebuilding:
Last reviewed: October 23, 2026