ADU Rules: Altadena vs Carson
How do adu rules rules compare between Altadena, CA and Carson, CA?
Carson has fewer restrictions than Altadena.
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 →Carson, CA
Los Angeles County
Carson allows accessory dwelling units (ADUs) and junior ADUs (JADUs) on parcels with existing or proposed single-family or multifamily dwellings, in conformance with state ADU law (Cal. Gov. Code §65852.2 and §65852.22). The Carson Municipal Code zoning chapter (Article IX, Chapter 1) implements these standards ministerially.
View full Carson rules →Key Facts Comparison
| Fact | Altadena | Carson |
|---|---|---|
| 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) | - |
| Governing law | - | Cal. Gov. Code §65852.2 (ADUs); §65852.22 (JADUs) |
| Local code | - | Carson Municipal Code Article IX, Ch. 1 (Zoning) |
| By-right ADU size | - | 800 sq ft, 16-ft height, 4-ft setbacks |
| Max detached ADU | - | 1,200 sq ft |
| JADU max | - | 500 sq ft (within existing SFD) |
| Review type | - | Ministerial (no public hearing) |
| Approval timeline | - | 60 days from complete application (state mandate) |
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.
Carson FAQ
Can Carson ban ADUs in single-family zones?
No. Gov. Code §65852.2 preempts local bans. Carson must allow ADUs ministerially on any single-family or multifamily lot.
Do I need a public hearing for an ADU?
No. State law requires ministerial (over-the-counter) approval within 60 days of a complete application.
Can I build an ADU and a JADU on the same lot?
Yes. State law allows one ADU plus one JADU on a single-family lot.
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