However, a few costly surprises can lurk behind the plaster walls and under the floorboards since these homes usually predate today’s building codes. You may find that the home’s plumbing, heating, and electrical systems need repair or replacement. And, while some renovations can wait, others may need to be addressed right away for insurance purposes.
For instance, knob and tube wiring (K&T) can make it challenging to buy or renew a home insurance policy.
What is knob and tube wiring?
K&T is a wiring method that was popular before the 1950s. It used long black wires wrapped in rubberized cloth fed through ceramic tubes in the home’s joists, meeting at connection points — the knobs. While no longer installed today, many older homes still use this electrical system.
How can you tell if a home has knob and tube wiring?
In homes with unfinished basements, looking at the ceiling should indicate the wiring, as it is often left exposed. Some other indicators will be antique light switches on the walls and the lack of three-pronged outlets.
It can be trickier to tell if a home has K&T, particularly if it has undergone some upgrades. Either way, having an electrical inspector come to the house is the best course of action.
Is knob and tube wiring dangerous?
K&T doesn’t age well — it’s around 70 to 100 years old, after all. Here are some of the issues that can arise:
- Wire damage. Often, the rubber coating cracks, exposing wires and becoming a fire risk.
- Circuit overload. The electrical system wasn’t designed for today’s demand and modern appliances. Many modern devices, like fridges and even computers, have three-pronged plugs which are unsuited to the older two-pronged outlets.
- Improper modifications. Using extension cords or modifying the K&T can be hazardous.
- Power surges. K&T has no grounding wire, so nothing protects the outlets and your appliances from sparking.
According to the Electrical Safety Authority (ESA), the regulatory body in Ontario, K&T is permitted if protected by a 15 A fuse or circuit breaker, no additional outlets have been added to the original installation, and the conductors appear to be in good condition.