The knob and tube wiring system is an early type of electrical wiring that can be found in many older homes.

It was initially developed during the 1880s and was installed in homes until the mid-1950s—but it has since been replaced by much safer alternatives. However, there are still plenty of homes with this outdated wiring system, so if you’re one of them, then listen up because we have all the information you need to know about knob and tube wiring dangers and how to replace it safely.

Electrical wires, Knob and tube wiring, on a residential renovation site

Knob and Tube Wiring: Everything You Need To Know

From about 1880 to the 1950s, knob and tube wiring was a standardized form of electrical wiring in homes. It consists of insulated copper wire that is fed throughout wooden beams using porcelain knobs and tubes. The tubes are placed through drilled holes in wooden joists, while the knobs are used to run the wires along wooden beams, keeping them from touching the frame.

This form of electrical wiring does not contain a ground wire, meaning it cannot power 3-prong electronics, which most of today uses. It also has been deemed relatively hazardous if poorly installed or maintained. Although not inherently dangerous on its own, it’s essential to know how to maintain it and consider replacing it to ensure safety in your home and provide enough power for all of your home’s appliances and devices.

The main differences of knob and tube wiring, compared to modern electrical wiring:

  • Not used after the 1950s
  • Has no ground wire
  • Cannot install insulation over it (risk of overheating)
  • Wires are insulated with rubber or cloth vs. plastic

Knob and Tube wiring

Does Knob and Tube Wiring Have to be Removed?

There are two times when it is considered absolutely necessary to remove the old knob and tube wiring and replace it with new electrical work: when you are reinsulating your home or if homeowner’s insurance won’t cover your home due to the old wiring. Although knob and tube wiring is obsolete and is no longer permitted in new builds, it’s also not 100% required to remove it in older homes.

However, it’s highly recommended you replace these old systems because of a few reasons.

  1. It can become very brittle over time. The covering on the wires is made of rubber or cloth and can easily wear away or shred over time, leaving wires susceptible to the elements and risk exposing a live wire.
  2. These were built on a two-prong system, and much of your appliances and electronics require a three-prong grounded outlet. Adapters can be used but put you at significant risk of overloading the system and blowing a fuse or circuit.
  3. If you ever want to re-insulate your home, knob and tube wiring must be removed because it cannot be covered due to its susceptibility to overheating. So get ahead of that issue and replace your k&t wiring with new electrical.
  4. New electrical systems work much more efficiently and require less maintenance to work appropriately.
  5. To eliminate the high risk of fire or blowing a fuse by replacing old, outdated electrical systems with newer, safer alternatives.

How to Maintain Knob and Tube Wiring

If you have an old home built pre-1950s, chances are you do have knob and tube wiring, and if you don’t want to spend the money rewiring your home (yet), there are a few things you can do to maintain it and keep it safe. Some ways to maintain existing knob and tube wiring include:

  • Having it regularly inspected by a professional electrician
  • Avoid using too many appliances at once
  • Ensure all outlets are installed with GFCI (ground fault circuit interrupter) outlets. These will reset if a circuit or fuse is blown.
  • If you have outlets in the kitchen, bathroom, laundry room, or other areas near water/sinks, you should replace those sections’ wiring. Only grounded wire systems are safe to use in these areas.
  • Perform regular repairs such as replacing frayed wire coverings or cracked tubes and knobs. Regular maintenance is key to avoiding unsafe conditions.
  • Consider getting your knob and tube wiring replaced, and spend time getting multiple estimates so you can budget appropriately. The best way to handle knob and tube wiring is to get it replaced and updated with new, safe electrical in your home.
  • DO NOT attempt to DIY any knob and tube wiring fixes or installs. Knob and tube electrical systems are at their highest risk of failure and fires when people attempt to fix it themselves. This should only be done by a professional who can navigate these older systems safely.

Steps to Replace K&T Wiring

Sadly if you have an aging knob and tube wiring system, you will likely need to have it removed and replaced. Tampering with it will only buy you time, and with all modern electricians using up-to-date systems, it makes it difficult to continue using an obsolete application like k&t. Also, it’s impossible to ground wire an existing knob and tube system to bring it up to date, so your best bet is to replace it all.

electrician installing knob and tube wiring

It’s also important to note that the first sign of exposed wires is when you should replace it. If a visible area of your copper wiring is exposed, chances are high it’s exposed somewhere else, which means your home is at risk of fire or other electrical issues.

Here are the steps to replacing knob and tube wiring you can take as a homeowner.

  1. Do not do it yourself. DIY electrical work is never recommended, but especially with an old system like this. It will be challenging to navigate, and finding replacement parts to work with can prove difficult.
  2. Call your local electrician like Electric City to do a full inspection of your home’s electrical.
  3. Get an estimate! The sooner you get an estimate, the sooner you can budget for your rewiring. It is not cheap, and you should expect to spend anywhere from $5,000 to $15,000 to rewire your entire home. The cost ranges greatly depending on the size and number of stories of your home.
  4. Schedule a time to get it done. You will likely need to be without electricity for a few days while the work gets done, so plan ahead and don’t leave a full fridge or freezer, and plan to spend the night elsewhere.
  5. Enjoy your new wiring! With new wiring installed, you can now run as many appliances as you like at once without worrying about blown fuses or loss of power.

expert electrician meeting a homeowner; knob and tube wiring

Call Electric City And Set Up Your FREE Inspection

If you need rewiring in your home, call Electric City. We can remove old wiring, replace it with new, efficient wiring in no time and with no hassle to you. Our dedicated team of technicians is here to make it easy for you. So whether you have knob and tube wiring in need of replacement or are just looking for an inspection, we can handle it all.


How do I know if I have knob and tube wiring?

Knob and tube wiring is a type of old wiring system that uses ceramic knobs and tubes to run electrical wires through walls and ceilings. If you have knob and tube wiring, you will usually see ceramic knobs attached to visible wires running through the walls and ceilings of your home.

What is bad about knob and tube wiring?

Knob and tube wiring is considered outdated and unsafe, as it is not up to modern safety standards. The insulation on the wiring can degrade over time, creating a fire hazard. Additionally, the wiring may not be suitable for modern electrical devices.

Can you live with knob and tube wiring?

It is not recommended to live in a home with knob and tube wiring, as it is outdated and unsafe. If you do live in a home with knob and tube wiring, you should have a qualified electrician inspect the wiring and make any necessary repairs or upgrades.