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If you’ve ever watched a home improvement show, or anything involving brothers and properties, then you probably shudder if you hear the words “knob and tube”. Knob and tube wiring was an affordable, easy way to install electrical from the late 1880’s into the 1930’s, but today it’s clearly outdated. That said, it’s had a bit of a bum rap, so we’ve provided the shocking truth about knob and tube wiring here to clear up any confusion or panic it might be causing.

What is knob and tube wiring?

Knob and tube wiring consists of porcelain tubes used with simple copper wires that were installed in the walls between porcelain knobs. The system provided tension to keep the wires away from the wood framing of the house which is important because electrical currents tend to cause them to heat up. Not the greatest combination, heat and wood. Anyways, they did the job required to service a 60-amp main service panel back in the day, but today’s household has cranked everything up more than a few notches and you realistically need a panel for at least 150-amp. Combine this with the fact they’re very old and can be worn, and you can see why they’ve got a rep for being unsafe.

Why it matters if you are buying or selling an older house

Despite popular belief, knob and tube wiring is still considered safe according to both the Electrical Safety Authority and the Ontario Electrical Safety Code. This of course comes with the caveat that not all knob and tube wiring is in prime condition. That brings us to some common issues associated with knob and tube:

  • There’s no ground wire to handle power surges and overloads.
  • Modern insulation and knob and tube don’t mix, as knob and tube needs to breathe. If you have modern insulation you increase the danger of fire.
  • The sheathing used for knob and tube wiring is actually made of cotton which breaks down over time. This means you can have exposed wires in the walls which can cause not only fire, but electrical shocks.
  • A lot of homeowners try to compensate for the 10-amp knob and tube by adding a larger 15-amp fuse which is very dangerous as it can overload the system. Combine this with new appliances and other household demands, and it gets even worse.

Knob and tube red flags

According to the Electrical Safety Authority you can look for red flags that’ll tell you a homeowner is trying to compensate for their knob and tube wiring including:

  • Using extension cords in place of updated or permanent wiring
  • Replacing 10- or 15-amp fuses with 20 or 30 amps
  • DIY upgrades such as receptacles and outlets on existing circuits
  • Improper replacement of two pin receptacles

If you notice anything like this, you’ll know that there’re potential issues with electrical in a home. However, it’s always safest to depend on a home inspection to reveal true problems!

Commonly asked knob and tube questions

If you do find you have knob and tube wiring in your home, or a home you are considering buying, here’re some common questions to consider:

Is knob and tube wiring safe?

It can be as long as it has been well maintained. As mentioned, it’s an accepted mode of wiring by both the Electrical Safety Authority and the Ontario Electrical Safety Code. However, you should have a qualified electrical contractor inspect your wiring for damage. This is best done by the ESA which will help you identify any safety concerns.

Do I need to replace knob and tube wiring?

Not necessarily. Your best bet is to have an inspection done and base your decision on what the inspection reveals.  

Do I have to tear down my walls to replace knob and tube?

No. A qualified electrician can punch holes in the wall to reach the wires and make corrections and upgrades as required. Depending on the condition determined by your inspection, you might be able to avoid the cost of a full replacement and instead it can be disconnected so it doesn’t pose a risk. An electrician can ensure it’s completely disconnected during the rewiring process.

As you can see, despite its reputation there’re still conditions in which knob and tube can still be considered safe. Just remember the only person to confirm this is a certified electrician or a member of the ESA!

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