ADU Rules: Castaic vs El Monte
How do adu rules rules compare between Castaic, CA and El Monte, CA?
Castaic and El Monte have similar restriction levels.
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 →El Monte, CA
Los Angeles County
El Monte Municipal Code Chapter 17.110 regulates Accessory Dwelling Units (ADUs) and Junior ADUs per California Government Code Sections 66314-66339. Detached ADUs may be up to 1,200 sq ft; attached up to 800 sq ft or 50% of the primary dwelling.
View full El Monte rules →Key Facts Comparison
| Fact | Castaic | El Monte |
|---|---|---|
| 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) | - |
| Code Section | - | EMMC Ch. 17.110 |
| Detached Max | - | 1,200 sq ft |
| Attached Max | - | 800 sq ft or 50% of primary |
| Max Per Lot | - | 2 ADUs + 1 JADU |
| STR Use | - | Prohibited |
| Building & Safety | - | (626) 580-2037 |
Highlighted rows indicate differences between cities.
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).
El Monte FAQ
How big can an ADU be in El Monte?
Detached ADUs may be up to 1,200 sq ft. Attached ADUs up to 800 sq ft or 50% of the primary dwelling. Up to 2 ADUs and 1 JADU per single-family lot.
Can I convert my El Monte garage to an ADU?
Yes. Garage conversions to ADUs are permitted under California state law and El Monte's Chapter 17.110. A building permit is required.
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