Garage Conversions: Castaic vs Topanga
How do garage conversions rules compare between Castaic, CA and Topanga, CA?
Castaic and Topanga have similar restriction levels.
Castaic, CA
Los Angeles County
Garage conversions to ADUs in unincorporated Castaic are governed by LA County Code Title 22 §22.140.640 and California Government Code §65852.2. No replacement parking is required when an existing garage is converted, and the existing garage's setbacks are grandfathered. Properties in Very High Fire Hazard Severity Zones also trigger Chapter 7A wildland-urban interface standards.
View full Castaic rules →Topanga, CA
Los Angeles County
Garage conversions to ADUs in unincorporated Topanga are governed by LA County Code Title 22 §22.140.640 and California Government Code §65852.2. No replacement parking is required when a garage is converted to an ADU, and existing setbacks are preserved. A Coastal Development Permit applies in the Santa Monica Mountains Local Coastal Program area.
View full Topanga rules →Key Facts Comparison
| Fact | Castaic | Topanga |
|---|---|---|
| Governing Code | LA County Code §22.140.640 | LA County Code §22.140.640 |
| Replacement Parking | Not required | Not required |
| Existing Setbacks | Grandfathered | Grandfathered |
| Fire-Zone Construction | Chapter 7A in WUI areas | - |
| Permit Required | Yes — LA County building | Yes — LA County building |
| Coastal Permit | - | Required in SMM LCP |
Highlighted rows indicate differences between cities.
Castaic FAQ
Do I need to add parking if I convert my Castaic garage to an ADU?
No. Cal. Gov Code §65852.2 and LA County Code §22.140.640 prohibit the county from requiring replacement parking when a garage is converted to an ADU.
Are fire-resistant materials required for a Castaic garage conversion?
Yes, where the property is in a Very High Fire Hazard Severity Zone. Chapter 7A of the California Building Code requires ignition-resistant siding, eaves, vents, windows, and roofing in WUI areas.
Who issues a Castaic garage conversion permit?
LA County Public Works (Building & Safety) issues the building permit; LA County Regional Planning handles the ministerial ADU planning review under §22.140.640.
Topanga FAQ
Do I need to add parking if I convert my Topanga garage to an ADU?
No. Cal. Gov Code §65852.2 and LA County Code §22.140.640 prohibit the county from requiring replacement parking when a garage is converted to an ADU.
Do I still need a Coastal Development Permit for a garage conversion?
Yes, typically. Most Topanga properties fall within the certified Santa Monica Mountains LCP, so a CDP is required in addition to the building permit unless a categorical exclusion applies.
Who issues the permit for a Topanga garage conversion?
LA County Public Works (Building & Safety) issues the building permit; LA County Regional Planning processes the ministerial ADU review and any Coastal Development Permit.
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