What You Need to Know About Knob and Tube Wiring in Your Main Line Home

If you live in the Main Line area and your home was built anywhere between 1880 and 1950, there is a good chance it contains knob and tube (K&T) wiring.

While the technology, such as it is, still works well today, it is not “up to code” as far as most insurance companies are concerned. From a homeowner standpoint, most don’t even know they have such an issue until it comes time to remodel.

Knob and Tube Wiring Explained

Homes that were built up until the mid-1960s commonly have knob and tube wiring. It uses a combination of knobs and tubes as insulators, as the name would imply.

Some of the most noticeable features include:

• Two wires (hot and neutral) and no ground wire
• The circuit lacks a ground conductor
• Wires are encased in fiber insulation or some kind of rubberized material
• Connections are made outside of the junction box
• Two-prong outlets as opposed to three-prong

K&T is easy to spot. If you see those telltale ceramic knobs with electrical wires running to and from them, it’s not much of a stretch to make that assumption.

The apparatus is generally nailed onto joists, the wires protected by tubes where they pass through the joists, but it is just as common to find them hidden inside the walls of your home – meaning you might have to open up some of the walls in order to pinpoint the location. However, if the wiring has been updated, such as if a socket or switch was replaced, this might become a bigger job pretty quickly. While some switches may have been replaced, K&T may still be an issue in other parts of the home or in the ceiling.

Potential Problems with Knob and Tube Wiring

Simple and functional, K&T wiring worked well for millions of households for almost a century. Its popularity was largely due to the fact that it was far less expensive to install than other types of wiring.

If it was installed correctly, is undamaged, and unmodified, it likely still works just fine – it even has some advantages! For instance, K&T uses copper wire that is larger in diameter. Larger wires run cooler. On the other hand, if you have knob and tube wiring, it is likely very old, which is a distinct disadvantage.

Courtesy of Dover Projects

Either way, most K&T is not compliant with current building codes so any upgrades or renovations would require a full rewire.

Some of the more concerning issues inherent to K&T design include:

1. There is no grounding conductor. This can result in shock, injury, and possibly fires.
2. The insulation around the wire degrades, either through wear or by rodents chewing on it.
3. Modern electrical needs exceed the capacity of K&T. This can cause the insulation to degrade, exposing the wire.
4. If foam insulation has been blown in around the area where the K&T wires are located, it could cause the wires to heat up and become a fire hazard.
5. K&T wiring only uses two-prong outlets, meaning that many of today’s appliances are not compatible.
6. K&T only supports 12 circuits. If more circuits were needed, they would have to be spliced into the existing wire, increasing the risk of overload, surges, fire, and injury.

Do I have to replace the knob and tube wiring in my Main Line home?

By law, you are not required to replace your knob and tube wiring. You are free to repair or modify the system and use it as you like. However, it is not permitted to install in new builds.

According to the code, an electrical system cannot be covered by insulation or located in attics, walls or ceilings that use certain types of insulation.

Additionally, most insurance policies address the issue of K&T wiring specifically. Some might include language that requires its removal prior to coverage, while others may require you to pay a higher premium or higher deductibles due to the elevated risk.

What You Need to Know About Knob and Tube Wiring for Your Remodeling Project

If you aren’t remodeling and everything is working as it should, there is really no need for you to replace your K&T wiring, but you should have it inspected on a regular basis. On the other hand, if you are planning an upgrade or a remodel of your kitchen, bathroom, or any part of your home, there is no better time to upgrade.

If you would like to learn more about knob and tube wiring or would like to discuss your next Main Line Philadelphia area home remodeling project, schedule a conversation today. We would love to hear about your remodeling plans and tell you how we can help.