I Have Knob & Tube Wiring

Estimated reading time: 3 minutes, 35 seconds

Knob & Tube with Splices

During almost every remodeling project Levco does, especially in Boise’s historic North End, we encounter Knob & Tube Wiring. It was the craze back in the late 1800’s to the early 1900’s, it was relatively safe ( compared to kerosene or gas lamps) and it was cheaper to install than the armored cable alternative.

Knobs are the porcelain insulators that are nailed in and keep the wires from touching. Tubes are the porcelain insulators that were stuck in holes that the wires would run through.

Danger occurred when splices were done improperly because poor connections caused heat and heat caused fires. Other problems included a fused neutral conductor and the ease for homeowners to add larger fuses when they continuously popped. Heat was dissipated through open air and truly the wires should have breathing room. Overloaded circuits are not uncommon in older homes because there were no previous requirements for the number of outlets.

Proper Junction Box

Knob & Tube was a system where single wires, a hot and a neutral, were run to each outlet and switch. When a wire came close to or was required to go through a wood member, it would also be attached to or go through a porcelain insulator. Splicing was done anywhere. The insulation was carved back, the new wire was wrapped tightly and ideally soldered, and then covered with electrical tape, which,in those days, was different and called friction tape.

The truth is that if your home has Knob & Tube wiring, and it still works well you are doing OK. With age, the insulation around the wires becomes brittle and is often disturbed during renovations. Aggravation occurs when a wiring problem crops up because the connections could be anywhere.

Rough Electrical

Take a complicated three way switch, for instance, with connections of other wires anywhere in line and power allowed to come from different circuits. You can see how solving a problem could be a nightmare.

These days all connections must be made in an accessible electrical box.

What is missing from knob & tube wiring is the ground wire which is an added safety element that has been an added feature to the code. There have been lots of upgrades in electricity delivery since those early days of electrifying homes.

Since the end of World War II, electrical gadgets have become common. These days we have far more electrical conveniences (necessities) in the home, which  requires more circuits, at least 4 in a modern kitchen.

According to my insurance agent you, may have trouble getting your home insured if they believe hat you have not updated your home and still have Knob & Tube wiring. If they see evidence of an undersized service panel (say 1oo amps or less) or old screw in fuses (because a 15 amp fused that is blowing frequently can easily be swapped out for a 30 amp, or a coin YIKES) which in turn could cause the wires to heat up so much that they catch something on fire.

At Levco, we only use licensed electricians to provide our electrical work.

Andy the Electrician

Most electricians are fluent in the old time wiring techniques. The ones we use  specialize in remodeling and don’t mind the intricacies of adding to an existing system or in some cases ripping out the old stuff back to where it is safe and going from there.

Like anything difficult, it takes a special subcontractor who has a passion for remodeling. If your wiring requires updating during the course of a remodeling project, you can rest assured, Levco will take care of any problems and upgrades your electrical system may need. Our motto is to “do as much as necessary yet as little as possible” to make you home safe and functional for years to come.

Your comments are welcome. To ask questions or get more information about remodeling, email me directly or visit our contact page.

Disclaimer: Some of these images came from the WEB. If they are yours, and you object to them being used, please claim them and I will gladly remove and replace them at once.


  • Maurice says:


    Nice blog.
    Can you comment about issues related to knob and tube in the attic or other places where you may want to add insulation that would envelope the wiring? Also do you know how insurance companies feel about knob and tube wiring? is there a discount if you remove it or don’t have it?


    • Joe Levitch says:

      I am looking into discounts for insurance, however I doubt that there are any. As far as adding insulation over Knob & Tube wiring…it is frowned upon for the reasons I mentioned re: heat dissipation, however there are no know cases of fire related to covering knob and tube wiring that I could find mention of. That being said, at least here in Idaho there is no prohibition for insulating over knob & tube wiring. Good question.

Leave a Reply