ADU Rules: Carson vs Castaic
How do adu rules rules compare between Carson, CA and Castaic, CA?
Carson has fewer restrictions than Castaic.
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 →Castaic, CA
Los Angeles County
Castaic 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 created in non-livable existing space.
View full Castaic rules →Key Facts Comparison
| Fact | Carson | Castaic |
|---|---|---|
| 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) | - |
| 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 |
| Side/Rear Setback | - | 4 ft (new construction) |
Highlighted rows indicate differences between cities.
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.
Castaic FAQ
Who regulates ADUs in Castaic?
Castaic is unincorporated, so LA County Regional Planning regulates ADUs under LA County Code Title 22 §22.140.640, not a separate city ordinance.
Are there fire-zone restrictions on Castaic ADUs?
Yes. Portions of Castaic are in LA County's Very High Fire Hazard Severity Zone, so ADUs must meet Chapter 7A wildland-urban interface ignition-resistant construction standards and LA County Fire Code §325 brush clearance.
Can a Castaic multifamily lot add detached ADUs?
Yes. Under LA County Code §22.140.640, multifamily lots may add up to two detached new-construction ADUs plus conversion ADUs within non-livable space (up to 25% of existing units).
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