If your house was built before about 1950, there is a good chance it started life with knob-and-tube wiring. We see it all the time in the older pockets of midtown Toronto, in parts of Forest Hill and in the century homes around Davisville.

Here is what it is, why insurers ask about it, and what it actually takes to deal with.

What knob-and-tube wiring is

Knob-and-tube was the standard wiring method in North American homes into the 1940s. Single insulated wires run through the framing, held away from the wood by ceramic knobs and passed through joists in ceramic tubes. There is no ground wire, and the hot and neutral run separately.

You can usually spot the giveaways in an unfinished basement or attic: white ceramic knobs on the joists, and two-prong outlets with no ground on the floors above.

Is it dangerous on its own?

Original, undisturbed knob-and-tube that was installed well is not automatically a fire hazard. The problems come from age and from what people have done to it over 70 or 80 years.

The real risks we find are:

  • Brittle, cracked insulation that has dried out over decades.
  • Knob-and-tube buried in blown-in attic insulation, which traps heat the system was never designed to handle.
  • Amateur splices and extensions where someone tapped into it to add outlets or a renovation.
  • No ground, so no protection for modern electronics and appliances.

Why your insurance company cares

Many Ontario home insurers will not write or renew a policy on a house with active knob-and-tube, or they charge more and demand it be removed within a set time. That is the most common reason people call us about it. If you are buying an older home, this is worth checking before you close.

What replacement involves

Dealing with knob-and-tube usually means rewiring the affected circuits with modern grounded cable, adding proper junction boxes, and often updating the panel at the same time. It needs an electrical permit and an ESA inspection, both of which we handle.

How big the job is depends on access. An open basement and attic make it faster. Plaster walls and finished ceilings mean more careful fishing of wires to avoid tearing up the house. We walk the home first and quote it properly, because every old Toronto house is a little different.

The honest advice

You do not always have to rip out every last piece in one weekend. But active knob-and-tube feeding your living space should be on a plan to replace, both for safety and for your insurance. If you are already opening walls for a renovation, that is the moment to do it.

Want someone to actually look at what you have? Get a free quote and we will tell you straight where you stand.