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 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 explains.
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 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 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 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 explains what that changes.
The AFCI and GFCI guide 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. 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 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 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 and the selling guide 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.