How many different kinds of wiring can be in my older home?

Did a licensed electrician do the rewiring? You may never know. ‘What happens behind the walls stays behind the walls.’

Understanding how to work with electricity requires broad electrical knowledge and extensive training to deal with the plethora of wiring systems, different voltages, legalities and provincial regulations. Electrical wires are the veins of a house; they keep the lights on and everything running safely and correctly.
Licensed electricians are specialists who must first dedicate 9,000 hours working as an apprentice under professional guidance before applying for their license.

Millions of homeowners decide to rewire or add outlets themselves, even knowing how complicated and potentially hazardous working with electrical wiring is for a do-it-yourselfer.

To rewire an older house, an electrician must fish new wires behind covered walls, through hidden wall bracings and above rafters, all without a clear view of the work they’re doing.

It is meticulous work.

The new wires need to be hooked up directly to the electrical panel, usually located in the basement. Typically, the old panel, which at one point, was able to handle the house’s lesser electrical needs will require a replacement with a larger panel to accept the load put on by a tsunami of electrically charged products in our contemporary homes.

Plumbing and electrical, two big jobs that must take place behind walls, are necessary upgrades that some house flippers will put off doing. If no one can see the work, many people will assume new outlet and switch plates means the wiring must be new.

‘Are you ready for 2022?

Plumbhouse Plumbing, Heating & Electrical is licensed to install Smart Home Electrical and Security Systems. Read more HERE, or give us a call at the number below.’

Here’s how to tell when rewiring hasn’t been done by a licensed electrician:

It is never money wasted to hire a licensed electrician to inspect your house’s electrical work.

• They will discover improperly wired outlets or fixtures, or old wiring systems that are hidden in the wall. Not only is this kind of work inadequately done, it is also a very real fire risk.

• Desperate house flippers have been known to do desperate things. They can cut old wiring just behind an electrical box and then connect shiny new white wire to the original.

• Home inspectors are under time crunches and they or homeowners can be easily fooled by seeing new outlets and switch plates. An electrician should be hired to look deeper into the wall.

• If the electrical panel is original to a house built before 1950, it is likely time for the house to be rewired and its electrical panel upgraded. An electrical panel is a wall mounted board usually in the basement feeding many wires up into the house walls.

A quick look at the kinds of older house wiring that may be in your home:


Knob and Tube was used pre-1950 in Canada.

It’s easy to tell if you have a knob and tube system. Charmingly, it uses smooth porcelain knobs, rough-textured porcelain tubes, with costly and perfectly conductive copper wiring. It was a well-constructed two-wire system that remained popular until ground wires became a safety feature.

Knob and tube functioned well, but relied on air circulation around it to prevent overheating. The introduction of home insulation made the free movement of air around the wires almost impossible.

Knob and tube wiring became problematic for five reasons:

• House insulation became a popular product in the ’50s to prevent heat loss. However, the knob and tube wiring which required air circulation, overheated when surrounded by the insulation.
• The original protective rubbercloth casing eventually cracked off from age, exposing the copper wires. Exposed two-wire systems are extremely dangerous.
• Its two-wire system was not conducive with contemporary, three prong plugs. Changing two prong outlets to three tested the fragility of the knob and tube wires. More importantly, a home’s electrical system did not have ground wires.
• The risk of electric shock in a room with moisture close by is real. The outlet may have three prongs but an actual ground is non-existent. A homeowner may be unaware their electrical system is knob and tube and therefore without a ground wire.
• Knob and tube uses a 60-amp electrical panel. Houses must have a minimum 100-amp panel to qualify for regular house insurance in Canada. You may be denied insurance or be required to pay a higher premium or deductible.

Aluminum wiring has many concerns:

Between 1965 and 1974, aluminum wiring was a cost-saving alternative to the more expensive copper wiring of the knob and tube system.

It took until the mid-1970s for everyone to realize aluminum was at times a fire hazard caused from overheating at the often time thin connection points. You can tell you have aluminum wiring by the horizontal grey coloured cable on your electrical panel. It will be marked AL, ALUM or ALUMINUM.

Aluminum wire systems are problematic for five reasons:

• It is softer than copper so it can stretch. This causes connections to loosen, fail, spark or light on fire.
• It is not a pure metal; rather, it’s made of alloys. This also contributes to its sporadic connections.
• You may notice your lights flickering or feel that cover plates are very warm.
• Insurance companies are unlikely to insure your house with aluminum wiring. You should have a written inspection done by a licensed electrician, signed and dated to help convince an insurance company that it may be safe.
• If you choose to keep your aluminum, ask the electrician whether they have worked in a differently with aluminum. Marrettes, strippers, and pliers will all damage soft aluminum wire.

Are you buying a new home or wondering how safe your existing wiring is?

Plumbhouse Plumbing, Heating & Electrical will inspect your electrical system and make recommendations.

Please call us in the London Ontario area: (519) 453 4650.

Categorised in: Electrical