Castaic's Accessory Structures: The Rules That Matter

Every city handles accessory structures a little differently. In Castaic, California, there are 2 distinct rules that residents and property owners should be aware of. Some are stricter than what neighboring cities enforce, and others are more relaxed. Here is what you need to know.

Garage Conversions

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.

Key details: Governing Code: LA County Code §22.140.640. Replacement Parking: Not required. Existing Setbacks: Grandfathered. Fire-Zone Construction: Chapter 7A in WUI areas. Permit Required: Yes — LA County building.

Converting a Castaic garage to habitable space without a building permit is a violation of LA County Code, subject to stop-work orders, fines, and required after-the-fact permits or restoration. Non-Chapter 7A construction in fire-hazard zones may also be cited by LA County Fire.

ADU Rules

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.

Key details: 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).

Unpermitted ADUs in unincorporated Castaic are violations of LA County Code Title 22 enforced by LA County Public Works and Code Enforcement, with stop-work orders, daily-accruing fines, and required permitting. WUI-zone violations (e.g., non-ignition-resistant materials in fire-hazard zones) carry separate citations.

The Bottom Line

Castaic's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Castaic is broadly strict or permissive.

Keep in mind that Castaic can amend these rules at any council meeting. For the most current version of any rule mentioned here, check the specific ordinance page, where we track updates as they happen.