# Is knob and tube wiring legal in California?

> Existing knob and tube is legal in California. See what the code allows, when work needs a permit, the insulation rule and who may do it, then plan your job.

URL: https://laknobandtube.com/guide/is-knob-and-tube-legal-in-california/

Existing wiring, new work, the insulation rule, permits and licensing, and how the state code is enforced in Los Angeles and nearby cities.

Last Updated: October 24, 2026

Yes. Existing knob and tube wiring is legal in California, and no state rule requires removing it. The California Electrical Code treats it as an existing condition and controls new work instead: repairs, alterations and extensions need a permit and inspection, new circuits use modern wiring, and insulation may not surround it without a certified survey.

[LA Knob and Tube](https://laknobandtube.com/) replaces knob and tube wiring across Los Angeles, Pasadena, Glendale and South Pasadena, and every job runs on a city permit with inspection. This guide separates what the law allows you to keep from what it controls when anything changes. The short version is that legality is rarely what forces a rewire; insurance, a sale or an insulation project usually is, as the [knob and tube wiring guide](https://laknobandtube.com/guide/knob-and-tube-wiring/) explains.

Key takeaways

- No California rule requires existing knob and tube to be removed
- Repairs, alterations and extensions need a permit and inspection
- Insulation around knob and tube needs a licensed electrical contractor's certification first
- Replaced or extended circuits must meet current AFCI, GFCI and tamper-resistant rules
- The work is done by a C-10 licensed contractor, or by an owner-occupant under LADBS owner-builder rules

## Existing condition versus new work

The code draws its line at change. Wiring that was legal when installed, and has not been altered, is an existing condition. Nobody is required to tear it out because the code has moved on, in the same way an older house is not required to add every modern outlet the code now asks for in new construction.

Once something changes, the rules for the new work apply. Adding an outlet, extending a circuit, replacing a run, moving a fixture or swapping a fuse box for a [breaker panel](https://laknobandtube.com/electrical-panel-upgrade/) are all electrical work that needs a permit. The California exception in the knob and tube article says it directly: repairs, alterations or extensions to the electrical system will require permits and inspections by the authority having jurisdiction.

That is also where an electrical code assessment earns its place. An electrician looking at a knob and tube house is not checking whether it matches today’s code, because it will not. The useful questions are whether the existing system is in sound condition, whether earlier alterations were done properly, and what the code will require of the specific work being planned. The [inspection page](https://laknobandtube.com/knob-and-tube-inspection/) describes what that first visit maps.

## Which edition of the code applies

California’s electrical rules are the California Electrical Code, Part 3 of the state’s Title 24 building standards. The current edition is the 2025 California Electrical Code, which is the 2023 National Electrical Code with California amendments, in force since January 1, 2026. The California Building Standards Commission approved it, with the Department of Housing and Community Development responsible for the residential amendments.

The County of Los Angeles adopted the same edition by reference for unincorporated areas and the cities that contract with the county for building services, also effective January 1, 2026. In the City of Los Angeles, LADBS issues electrical permits and enforces the state code. Pasadena, Glendale and South Pasadena run their own building departments, and any local amendment there is confirmed per address with that city.

## The insulation rule: section 394.12

The one place the code speaks directly to existing knob and tube is insulation. Section 394.12 of the knob and tube article says concealed knob and tube shall not be used in the hollow spaces of walls, ceilings and attics where loose, rolled or foamed-in-place insulation envelops the conductors. The reason is heat: the system was designed to cool in open air.

California adds an exception that allows insulation where knob and tube is present if a California-licensed electrical contractor surveys the wiring and certifies it is in good condition, with no deterioration, no improper overcurrent protection and no improper connections or splices. The certification is filed with the building department and a copy goes to the owner. The insulation contractor posts caution notices in English and Spanish in every accessible area, and the insulation must be noncombustible and contain no conductive material. The Building Standards Commission’s rulemaking for the current edition carried that exception forward unchanged.

This is the rule most likely to make knob and tube a legal issue for an LA owner, because it comes up whenever an attic is insulated. The [attic insulation page](https://laknobandtube.com/knob-and-tube-attic-insulation/) compares the certification path with replacing the attic circuits first.

## What the code asks of replaced circuits

When knob and tube is replaced, the new circuits are built to the current code, and that changes more than the cable.

- **Arc-fault protection.** Under section 210.12, when branch-circuit wiring is modified, replaced or extended in kitchens, living and dining rooms, bedrooms, hallways, closets, laundry areas and similar rooms, it needs AFCI protection, from a combination AFCI breaker or an outlet-branch AFCI at the first receptacle. Short extensions of six feet or less with no added outlets are an exception.
- **Ground-fault protection.** Section 210.8 lists the dwelling locations that need GFCI protection, including kitchens, bathrooms, laundry areas and other wet or damp locations.
- **Tamper-resistant receptacles.** Section 406.12 requires them for nearly all standard receptacles in dwellings.
- **Grounding.** New cable includes an equipment grounding conductor, which knob and tube never had; the [three-prong outlets guide](https://laknobandtube.com/guide/knob-and-tube-three-prong-outlets/) explains what that changes.

The [AFCI and GFCI guide](https://laknobandtube.com/guide/afci-gfci-knob-and-tube/) explains what those devices detect and what they cannot do on old circuits that stay.

## Permits in the City of Los Angeles and nearby

Rewiring is permitted work everywhere in our [service area](https://laknobandtube.com/service-areas/). In the City of Los Angeles, LADBS issues the electrical permit. Its open data shows how routine that is: of 3,897 electrical permits on one- and two-family houses from January 2020 to October 2026 whose description mentions rewiring or knob and tube, 3,896 were issued as express permits without plan check. An LADBS inspector checks the new wiring before walls and ceilings are closed and again at the end.

Pasadena, Glendale and South Pasadena permit through their own building departments, and their fees, inspection steps and any local rules are confirmed per address. The [Los Angeles rewiring permit guide](https://laknobandtube.com/guide/los-angeles-rewiring-permit/) covers the LADBS process in detail.

## Who may do the work

In California, electrical work for hire is done by a contractor licensed by the Contractors State License Board. The C-10 Electrical Contractor classification covers placing, installing and connecting electrical wiring, fixtures and equipment. The people doing electrical work for a C-10 contractor are generally required to hold a state electrician certification under Labor Code section 108.

An owner can do the work on their own home only under owner-builder rules. LADBS issues an owner-builder electrical permit on a single-family house only with proof of ownership and proof that the owner currently lives at the address, and the owner signs an owner-builder declaration. An owner who rents the house out, or a friend helping, does not qualify. Even where the rules allow it, rewiring around brittle, possibly energized century-old conductors is not work to learn on.

[LA Knob and Tube](https://laknobandtube.com/) offers and manages knob and tube replacement; the work is carried out by licensed and insured electrical contractors who pull the permit and meet the inspector.

## Where legal and insurable part ways

A house can be fully legal and still hard to insure. Carriers write their own rules, and some decline houses with active knob and tube regardless of its code status. Since January 1, 2026, California sellers also give buyers a written electrical advisory under Civil Code section 1102.6i, which warns that faulty wiring can make insurance harder to get. Neither of those is a code requirement to rewire, but both often decide the timing. The [insurance guide](https://laknobandtube.com/guide/knob-and-tube-insurance-california/) and the [selling guide](https://laknobandtube.com/guide/selling-a-house-with-knob-and-tube/) cover them.

If you are planning insulation, a remodel or a sale and want to know which rules your project will trigger, a call is the simplest way to start.

## Questions about this guide

### Can an owner-builder permit cover knob and tube work on a rented house in Los Angeles?

No. LADBS issues an owner-builder electrical permit on a single-family house only with proof of ownership and proof that the owner currently lives there. An owner who rents the house out needs a contractor licensed by the CSLB, typically in the C-10 electrical classification, to pull the permit.

### Did the current California Electrical Code change the knob and tube rules?

Not for insulation. The edition in force since January 1, 2026 carried the California exception for insulating over knob and tube forward unchanged. Arc-fault, ground-fault and tamper-resistant requirements apply to new and modified circuits under the current edition.

### Do I need a permit to add an outlet to an existing knob and tube circuit?

Yes. Repairs, alterations and extensions to the electrical system need permits and inspections from the local building department. In practice the new outlet is fed by modern cable, and an electrician will also look at whether the old circuit can safely carry more load at all.

## More guides

- Learn [What is knob and tube wiring, and what should an LA homeowner do about it?](https://laknobandtube.com/guide/knob-and-tube-wiring/)How the system works, why it was a sound design in its day, what goes wrong with it now, and how Los Angeles owners decide what to do.
- Learn [Do you need an electrical permit for rewiring in Los Angeles, and how does it work?](https://laknobandtube.com/guide/los-angeles-rewiring-permit/)Who issues it, who is allowed to pull it, what the inspector checks, and how Pasadena, Glendale and South Pasadena differ from LADBS.
- Learn [How does knob and tube affect home insurance in California?](https://laknobandtube.com/guide/knob-and-tube-insurance-california/)What carriers tend to ask, how to get their answer in writing, what an electrician's letter can and cannot say, and where the FAIR Plan fits.
- Decision Guide [What should you do when selling a house with knob and tube in California?](https://laknobandtube.com/guide/selling-a-house-with-knob-and-tube/)The disclosures every California seller gives, the choice between rewiring first and pricing it in, and the paperwork that keeps a partial job from becoming a surprise.
- Learn [Do AFCI and GFCI protection work on knob and tube wiring?](https://laknobandtube.com/guide/afci-gfci-knob-and-tube/)What each device senses, when the code requires them, and why they reduce some risks on old circuits without replacing the wiring.