ADU Rules: Altadena vs Santa Clarita
How do adu rules rules compare between Altadena, CA and Santa Clarita, CA?
Altadena and Santa Clarita 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 →Santa Clarita, CA
Los Angeles County
Santa Clarita allows ADUs under state law (AB 68, SB 13, AB 881) and local regulations. One ADU plus one JADU per single-family lot. ADUs in flood zones must comply with FEMA requirements. CA HCD reviewed and provided guidance on the city's ADU ordinance in 2023.
View full Santa Clarita rules →Key Facts Comparison
| Fact | Altadena | Santa Clarita |
|---|---|---|
| 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) | - |
| Allowed | - | 1 ADU + 1 JADU per single-family lot |
| Max Size | - | Up to 1,200 sq ft (detached) |
| Owner Occupancy | - | Not required (state law through 2025) |
| Flood Zones | - | Must comply with FEMA requirements |
| HCD Review | - | March 2023 guidance letter |
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.
Santa Clarita FAQ
Can I build an ADU in Santa Clarita?
Yes. California law requires the city to allow ADUs. You can build one ADU plus one JADU per single-family lot, up to 1,200 sq ft for a detached ADU.
Do I have to live on the property to have an ADU?
No. California state law suspended owner occupancy requirements through at least 2025.
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