Owning an older home means that you have to learn about its quirks. For homeowners who have a home built before 1950, one of the quirks might be electrical wiring that is unlike what is common in modern homes. Older homes might have knob and tube wiring in all or part of the electrical system. While this wiring was commonly used in the past, it’s unsuitable for modern homes and the electricity requirements of current appliances and devices.

If your home has knob and tube wiring, there are a few things that you need to know about this type of electrical system. This will help you understand more about your home and find ways to protect your biggest asset.

What Is Knob and Tube Wiring?

Knob and tube wiring was standard from the 1880s through the 1950s before being replaced by the electrical wiring used today. It uses wires running through porcelain tubing and ceramic brackets.

Unlike current electrical systems, knob and tube wiring does not have a ground wire. Instead, it only has two wires: the black wire, which carries the electricity from the breaker panel, and the white wire, which sends any unused electricity back. Because there isn’t a ground wire, knob and tube wiring can’t accommodate anything that uses a three-prong plug, which can be inconvenient for homeowners.

Old-style wiring is anchored by ceramic brackets placed on studs or on the lathe behind the walls of a home. In some cases, it was run through holes in floor joists. There wasn’t a standard for the distance between the ceramic anchoring knobs.

Another issue in homes with knob and tube wiring is that it’s often difficult to determine what wiring serves what areas of the home because there were no regulations regarding this. The only way to tell how wires run is to get the schematic diagram for the home. Without this, trial and error is the only other option when there is a problem.

Why May Knob and Tube Wiring Be Dangerous?

There are several reasons why knob and tube wiring is dangerous. It wasn’t regulated like today’s electrical systems, so it was often installed and maintained by homeowners and handymen instead of by licensed electricians. There’s a chance that the materials were substandard, and the installer did not handle the connections correctly.

The age of the wiring is the primary concern because it is likely that it has degraded over time. However, other problems complicate the issues associated with knob and tube wiring. For example, modern appliances have a higher electrical demand than what was common when knob and tube wiring was popular. Today’s convection and microwave ovens, dryers, and vacuums all place a continuous load on this older style of wiring that can lead to insulation failure and overheating.

In addition, the lack of a grounding in knob and tube wiring is a safety issue. In modern electrical systems, the ground wire acts as a safe path for electricity to run in the event of a short circuit. In the event of a short circuit, the ground wire will trip the circuit breaker or blow a fuse, which is preferable to the dangerous shock that would occur otherwise.

Another concern with knob and tube wiring is it can’t be encased in home insulation. Most homes have thick insulation to help control heating and cooling bills for the home. Homeowners who want to use insulation rolls or blown-in insulation won’t be able to do this in areas with knob and tube wiring. Instead, they will have to use more expensive insulation methods.

There’s also a risk of water contacting the wiring, which can lead to the wiring shorting out and catching fire. This hazard is more concerning when the wiring runs in the floor joists of a room where water is present. Bathrooms and kitchens are especially dangerous. Even when there is a plastic sheeting under the floor, there’s still a chance of seepage. There’s also a risk of condensation building up on the wires, which is also a risk.

When knob and tube wiring fails, it can cause a fire. This is one of the greatest dangers of this type of electrical wiring. You may smell burning rubber before this happens to give you a warning, but that is not always true.

What Can Homeowners Do About Knob and Tube Wiring?

Knob and tube wiring is obsolete. It can’t be used in new construction, and you can’t have worn knob and tube wiring replaced with the same kind. The only option that homeowners have is to replace the old wiring with new wiring that meets current building code requirements.

Replacing knob and tube wiring isn’t a do-it-yourself job. It requires obtaining permits and having an expert remove and replace the old wiring. Afterward, an inspection must be completed to ensure the work is up to code.

It is usually a multi-day process if you need to rewire your whole home. The power company must disconnect the electrical service to the house so our electricians can work safely. In some cases, a professional has to replace the electric service panel so it can keep up with the demands of the electrical appliances and devices in your home.

The good news is you can work with a professional electrician to set up the new wiring to accommodate a modern electrical load without the system becoming overworked. They will note what appliances and other items you usually use so that they can craft a wiring plan that meets your requirements.

Because the project involves removing parts of walls to access the electrical lines, some homeowners make this project part of a more extensive renovation. This is also when you can have new outlets or fixtures put in.

How Can Knob and Tube Wiring Impact Insurance?

If you are thinking about buying an older home, you should know how knob and tube wiring can affect home insurance. Knob and tube wiring is an automatic disqualifier for many insurance policies because of the perceived safety issues. An insurance company that allows knob and tube wiring may have strict limits on coverage, and some will have waivers that release them from liability if the knob and tube wiring leads to damage to the home.

In most cases, insurance companies require you to have an inspection of an older home’s electrical system before they will offer you coverage. This is because they know that some houses have a partial replacement of the knob and tube wiring. Common locations where knob and tube wiring might remain in these homes include attics, basements, and bedrooms. Before purchasing an older home, you should have a reputable electrician perform an inspection so that you know what you are in for.

Contact the Professionals

At Potts Electric, we are a family-owned company that has been serving the residents of Ellisville, MO for over 10 years. We are expert electricians who can perform electrical inspections, rewire homes, and replace outdated electric panels. Contact us today to schedule your appointment with one of our professionals.

company icon