What is Knob and Tube Wiring?

what is knob and tube wiring

What is Knob and Tube Wiring?

By: Gareth Kelly – Expert Electrician, Co-owner of Dream Team Home Services

What is Knob & Tube Wiring?

Do you know if your home has knob and tube wiring? How about when your home built?

If your home was built before 1950, there’s a good chance you have knob and tube wiring in your home. Of course, unless you’ve had your knob and tube system replaced.

Check out these housing statistics of our local area:

  • Delaware County – 84,110 homes built before 1950
  • Montgomery County – 89,583 homes built before 1950
  • Ardmore, PA – 3,588 homes built before 1950
  • Havertown, PA – 6,383 homes built before 1950
  • Drexel Hill, PA – 6,635 homes built before 1950

Between the 1880s and 1940s, this method of wiring was very common in North America. 

This wiring method is a huge electrical risk at hand for homeowners. The electrical system has been obsolete for decades. Some areas across the country still allowed knob and tubing wiring as late as the 1970s.

While this method might’ve work then, it most definitely does not work now. We’ll explain why. its a risk, and why it should be replaced.

How familiar are you with knob and tube wiring? If you’re not familiar at all, that’s okay. We put this knob and tube guide together for you. We want to share our knowledge, so you better understand this system if it’s in your home. After all, the safety of your home is key.

Knob and tube wiring, or K&T, is pretty self-explanatory when you see it. This method consists of electrical wiring protected by rubber and porcelain or ceramic tubes. The knobs are typically screwed or nailed to wood framing components to support the tubes.


This type of wiring setup is considered ancient in terms of electrical systems and causes many headaches. Not just for homeowners like we said earlier, but for electricians.

Furthermore, a big difference between today’s wiring methods and knob and tube is the system lacks a ground wire. This is the type of extra wire that runs into the earth – an important safety necessity.

Lack of a ground wire in knob and tube wiring increases the chances that you’ll start a fire if you overload circuits.

How to Find Knob & Tube In Your Home

If you’re considering buying an older house, you should know how to identify knob and tube wiring.

The wiring method will be pretty present in many older homes. So, look for knob and tube wiring in areas such as the basement or attic. Scan those areas for white, ceramic spool-looking knobs. You may see black wiring “snaking” through exposed wood framing. Use the picture above for reference.

If you’d rather a licensed electrician do the inspection, that’s something our team can help with. Our VIP members get an annual electrical inspection of their home included in their membership. Something to think about if you’re buying an older home.

It also should be noted, just because the rest of your home’s wiring may have been updated, doesn’t mean you no longer have knob and tube. There’s often still knob and tube wiring lingering in hard-to-access areas. 

Why Knob & Tube Wiring Needs to be Replaced

While back in the early 20th century and prior, this method may have worked. In today’s world, knob and tube does not work, especially from a safety standpoint.

These are a few reasons why knob and tube needs to be replaced:

  1. This method of wiring was used when homes had fewer power demands
    • The power demands in today’s homes will overload a knob and tube wiring system. Think about all the electronics being charged, all while watching cable TV, with our Internet routers running 24/7. That’s a lot compared to the 1950s.
  2. Use of three-prong outlets will increase the risk of fire
    • Knob and tube wiring has no ground wiring. The use of everyday appliances with three-prongs (refrigerators, computers, etc.) is a big fire risk.
  3. Insulation will increase the risk of fire
    • If insulation is added to the home and covers up wiring, contact will cause the insulation to catch fire.
  4. Insurance companies may not insure your home
    • Insurance companies do not mess around with this. This should be a sign to get any knob and tube wiring replaced in your home.

You Shouldn’t Panic if You Have It – First, it’s not the end of the world if you have knob and tube wiring in your home. Currently, there are no regulations or electrical codes that require K&T to be removed.

BUT, as we’ve referenced many of times, it is a safety hazard. We wouldn’t recommend putting of getting this wiring method replaced.

Our electricians have replaced knob and tube systems in a few different ways. They’ve completed the replacement room-by-room as the home is being updated, or they’ve done a complete home rewire. Our electricians accommodate the replacement in which it works best for you.

Don’t let the fear keep you up at night. You owe it to your home and loved ones to have it inspected, at the very least.

Due to the safety concerns, we highly recommend having these systems inspected and evaluated annually by a licensed electrician.

Schedule An Inspection

If you’re currently living in a home with knob and tube wiring and you’ve read this article, we hope you’ll pick up the phone and give us a call. We’ll schedule to get one of our knob and tube specialists out to your home.

If your home was built before 1950, and you’re not sure whether you have a knob and tube system, get our licensed electricians out there.

This type of wiring setup in a home is considered ancient and causes many headaches for homeowners.

Give our knob and tube specialists a call today and we’ll give you expert analysis.


By: Gareth Kelly – Expert Electrician, Co-owner of Dream Team Home Services

Author: Gareth Kelly

About The Author:

Gareth Kelly, co-owner of Dream Team, has been serving Delaware Valley homeowners for over 20 years with expert electrician services. He came from Ireland to the United States in 2000 and started his own business in 2001, Kelly Electric Co Inc. His expertise in the field grew and strengthened his connection and local commitment to the community. In 2018, Gareth partnered with one of his best friends to create Dream Team Home Services, Inc. Dream Team is about being the ultimate home services team for any homeowner with a reputation for trusted service.