ADU Rules: Altadena vs South San Gabriel
How do adu rules rules compare between Altadena, CA and South San Gabriel, CA?
Altadena and South San Gabriel have similar restriction levels.
Altadena, CA
Los Angeles County
Altadena is an unincorporated CDP in Los Angeles County governed by LA County Code Title 22 §22.140.640 (Accessory Dwelling Units and Junior Accessory Dwelling Units), most recently amended April 2024. Single-family lots may add one ADU plus one JADU; multifamily lots may add up to two detached new-construction ADUs plus conversion ADUs in non-livable existing space.
View full Altadena rules →South San Gabriel, CA
Los Angeles County
LA County's ADU Ordinance (amended October 2024) allows accessory dwelling units in all residential zones of unincorporated areas. Applications go through EPIC-LA and are reviewed by the Department of Regional Planning. Pre-approved plans are available.
View full South San Gabriel rules →Key Facts Comparison
| Fact | Altadena | South San Gabriel |
|---|---|---|
| Governing Code | LA County Code §22.140.640 | - |
| Single-Family | 1 ADU + 1 JADU per lot | - |
| Multifamily Detached | Up to 2 new (20 ft max) | - |
| WUI Fire Zone | Chapter 7A applies (hillside) | - |
| Side/Rear Setback | 4 ft (new construction) | 4 feet |
| Max ADU Size | - | 1,200 sq ft |
| JADU Max | - | 500 sq ft |
| Max Height | - | 16 feet |
| Application | - | EPIC-LA portal |
Highlighted rows indicate differences between cities.
Altadena FAQ
Who regulates ADUs in Altadena?
Altadena is unincorporated, so LA County Regional Planning regulates ADUs under LA County Code Title 22 §22.140.640, not a separate city ordinance.
Do hillside or fire rules apply to Altadena ADUs?
Yes. Altadena's hillside neighborhoods are in LA County's Very High Fire Hazard Severity Zone, requiring Chapter 7A ignition-resistant construction and Fire Code §325 brush clearance. Hillside-grading provisions of Title 22 apply on slopes steeper than 10%.
How big can my Altadena ADU be?
Under §22.140.640, a detached ADU on a single-family lot may be up to 1,200 sq ft; multifamily-lot ADUs have no maximum size cap. JADUs are capped at 500 sq ft.
South San Gabriel FAQ
Can I build an ADU in unincorporated LA County?
Yes. One ADU and one JADU are allowed per lot in all residential zones. Detached ADUs can be up to 1,200 square feet. Apply through the EPIC-LA portal.
Do I need to live on-site to have an ADU in LA County?
No. California state law eliminates owner-occupancy requirements for ADUs. You can rent both the main home and the ADU.
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