Castaic Homeowner Guide: Unincorporated LA County Permits and ADUs

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Last updated November 13, 2026. Reviewed by the Cash Home Buyers CA team.

Castaic is an unincorporated community of Los Angeles County, so there is no city hall. County departments handle planning, building permits and many enforcement matters. This guide explains the area plan that governs Castaic, the county’s building and ADU pages, and what to do before selling a house with open permit or code issues.

Governing jurisdiction	Los Angeles County (unincorporated)
Area plan	Santa Clarita Valley Area Plan, adopted Nov. 27, 2012, effective Dec. 27, 2012
Building permits	LA County Public Works, Building and Safety Division; headquarters at 900 S. Fremont Ave., Alhambra
HQ hours	7 a.m. to 5 p.m., Monday to Thursday; over-the-counter plan review 7 to 11 a.m., Monday to Thursday
Property rehabilitation and code enforcement	(626) 458-3193 (Building and Safety)
ADU reviewers	LA County Planning and Public Works Building and Safety

The Santa Clarita Valley Area Plan

LA County Planning says the Santa Clarita Valley Area Plan was adopted by the Board of Supervisors on November 27, 2012 and took effect on December 27, 2012.

It is a component of the County General Plan, with goals, objectives, policies and implementation actions that apply only to the unincorporated parts of the Santa Clarita Valley, and it is part of a joint planning effort with the City of Santa Clarita called One Valley One Vision.

The county adopted two ordinances amending Title 22 (Planning and Zoning) at the same time, and a Trails Map adopted in 2007 and an Area Plan Maintenance Project adopted October 30, 2018 are also listed.

That plan is what sets land-use direction for Castaic, and your lot’s zoning comes from Title 22. We did not find an official fire-hazard, hillside or historic-district designation for Castaic on the pages we reviewed, and we are not asserting one. Ask County Planning to confirm zoning and any overlays for your parcel.

Building permits in unincorporated Los Angeles County

The county’s Building and Safety Division, part of Public Works, provides building permits, plan review and inspection for unincorporated communities. It describes its services as delivered through headquarters, district offices and contract city offices. The headquarters is on the third floor at 900 S.

Fremont Avenue, Alhambra, open 7 a.m. to 5 p.m. Monday through Thursday, with over-the-counter plan review from 7 to 11 a.m. on those days. The division also uses an electronic permitting and plan review system called EPIC-LA.

The page we reviewed does not name which district office serves Castaic, so confirm that with the division.

Phone numbers listed include (626) 458-3173 for building plan check, (626) 458-3180 for electrical, (626) 458-3182 for mechanical and plumbing, and (626) 458-6333 for grading and drainage.

Code enforcement and property rehabilitation

Building and Safety lists a property rehabilitation program for substandard and unsightly buildings and properties, a Building Rehabilitation Appeals Board, and district office and Nuisance Abatement Team code enforcement focused on unpermitted grading and construction within unincorporated areas. Its property rehabilitation and code enforcement line is (626) 458-3193. Zoning complaints are handled separately; LA County Planning says it responds to zoning complaints in unincorporated areas.

We did not find county pages with specific fine amounts, so check with the office for any fees or liens attached to a case.

ADUs in the county

LA County Planning defines an accessory dwelling unit as a unit with a full kitchen and bathroom that is accessory to a residence, attached or detached. A junior ADU has a 500-square-foot maximum size, must be within the main home and needs its own exterior entrance.

Both LA County Planning and Building and Safety review ADUs. The page we checked does not list setbacks, heights or fees, so get those from the county before designing a unit. Public Works has published a handout on legalizing unpermitted ADUs and JADUs built before January 1, 2020 under AB 2533.

Selling a Castaic house as-is

You must disclose known material facts. A cash buyer can purchase the house as-is, leaving permit questions and violations for after closing. Collect permits, final inspection records and county notices. Because Castaic is next to the City of Santa Clarita, see our Santa Clarita building permits guide for the neighboring city’s rules, which do not apply to unincorporated lots. Tax questions are covered in our county property tax guide.

How to sell a house in Castaic

Ask County Building and Safety for the permit record.
Gather permits, final inspections and county notices.
Request a no-obligation cash offer for the house as it stands.
Choose your closing date.
Close with no repairs, permit cleanup or showings required.

See also our Castaic page and the Los Angeles County hub.

Own a Castaic home with unpermitted work or violations? Sell as-is for cash.

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Frequently asked questions

Is Castaic a city?

No. Castaic is an unincorporated community of Los Angeles County, so county departments handle planning and permits.

Which plan governs Castaic?

The Santa Clarita Valley Area Plan, adopted November 27, 2012, applies to unincorporated parts of the Santa Clarita Valley.

Who issues building permits in Castaic?

LA County Public Works, Building and Safety Division.

How big can a junior ADU be in LA County?

LA County Planning lists a 500-square-foot maximum, inside the main home with its own exterior access.

Do Santa Clarita city rules apply to Castaic?

Not to unincorporated lots. The city rules apply only inside the City of Santa Clarita.

Can I sell my Castaic house with unpermitted work?

Yes. You can disclose it and sell as-is, including to a cash buyer. Our statewide guide explains the disclosure rules.

More guides

Sources

This guide is general information from public sources, not legal advice. Confirm current rules, fees and hours with the city.