Knob and Tube Wiring: Everything You Need to Know

Everything You Need to Know When You Find Knob and Tube Wiring in an Older New England Home

If you’re looking at charming older homes in Concord or throughout New Hampshire, there’s a good chance you’ll come across something called knob and tube wiring. While these homes often have beautiful bones and historic character, this outdated electrical system can raise a few red flags for buyers and homeowners alike. It is important to assess and address the safety concerns associated with a home's knob and tube system.

Here’s what you need to know if you find knob and tube wiring in a New England property. Professional electrical inspections are crucial, and hiring qualified electrical contractors experienced with knob and tube systems is essential to ensure the integrity and safety of the electrical work.

What Is Knob and Tube Wiring?

Knob and tube (often shortened to K&T) is an early type of electrical wiring commonly used in homes built between 1880 and 1940. It consists of:

• Ceramic knobs that support wires

• Ceramic tubes that protect wires as they pass through wooden framing

However, tube conductors present challenges and safety concerns due to outdated materials and design, which can lead to significant hazards such as overheating and electromagnetic fields.

At the time, it was an innovative solution—but it wasn’t designed for today’s electrical demands. Understanding the distinctions between hot and neutral wires in knob and tube wiring is crucial, as improper handling can pose risks like overheating, especially under modern electrical loads.

Why It’s a Concern for Homeowners and Buyers

While K&T wiring isn’t inherently dangerous if untouched and properly maintained, it does present several issues:

No Grounding

One of the most significant issues with knob and tube wiring is the lack of a grounding conductor. Without a proper grounding conductor, modern receptacles cannot be installed in compliance with electrical codes, which raises significant risks, particularly involving heat management in circuits. Upgrading to grounded wiring is essential to ensure safety and adhere to building regulations.

Fire Risk

Knob and tube wiring is a significant fire hazard due to its inability to safely handle modern electrical loads. Insulation around this wiring can cause heat buildup, further increasing the risk of fire, which has led many insurance companies to refuse coverage for homes with this outdated system.

Outdated Capacity

It was designed before modern appliances and electronics—meaning it may not safely handle today’s load. The rise in the number and intensity of electrical devices used today has led to an increased demand for electrical loads, revealing that many existing knob and tube systems cannot meet these current requirements.

Fire Risk

Old insulation can deteriorate, and if improperly modified over the years, it increases the risk of overheating or sparking. The absence of proper air circulation due to insulation can create hazardous conditions, as it hinders the wires' ability to dissipate heat, leading to overheating and increased fire risk. During rewiring projects, it is also necessary to carefully preserve exposed insulation on knob and tube wiring. Electricians must take special precautions, such as using 600-volt rated tape or shrink tubing, to maintain the integrity of the exposed insulation while ensuring safety and compliance with electrical codes.

No Grounding

K&T lacks grounding, which protects both people and devices from electrical faults. Upgrading to grounded branch circuit wiring is crucial to ensure safety and adhere to building regulations, as it helps prevent potential issues with ungrounded conductors and maintains code compliance.

Insurance Challenges

Many home insurance companies won’t insure properties with active K&T wiring, or they’ll charge a much higher premium. Knob and tube electrical wiring affects insurance rates and availability, with a growing trend of insurers either refusing coverage or adjusting terms to account for potential replacement costs due to the risks associated with knob & tube systems.

How to Know If a Home Has Knob and Tube Wiring

If you’re working with a trusted home inspector, they’ll usually spot it right away—especially in attics, basements, or behind access panels. Still, it’s worth asking directly when touring older homes:

• Has the wiring been updated?

• Is there any active K&T still in use?

• Has the home been inspected recently for electrical safety?

Additionally, having the wiring professionally inspected is crucial to ensure safety and compliance with electrical codes. This is especially important for outdated Knob and Tube systems, as professional inspections can help identify potential hazards and provide options for complete rewiring or selective updates.

Wiring Methods and Alternatives

Knob and tube wiring is an outdated electrical wiring method that was widely used in North America from the 1880s to the 1940s. While it was once considered a safe and reliable method, it has since been replaced by more modern and efficient wiring methods. In this section, we will explore some of the wiring methods and alternatives that have replaced knob and tube wiring.

What to Do If You Find It

If knob and tube wiring is present, you have a few options:

Get a Professional Inspection

First, get a professional inspection to determine the condition of the wiring. A certified electrician should evaluate the wiring to assess the safety concerns and compliance with local building codes. Replacing knob and tube wiring is often necessary to ensure the safety of your home, and a professional can provide options for complete rewiring or partial upgrades.

Factor It Into Your Budget

Next, factor the cost of any necessary upgrades into your budget. The risks associated with old wiring, such as potential fire hazards and code compliance issues, make it essential to conduct thorough inspections. Upgrading outdated electrical systems can be costly, but it is crucial for the safety and functionality of your home.

1. Get a Professional Inspection

Hire a licensed electrician to assess the system’s condition and determine if replacement is necessary. A good electrical contractor can showcase their expertise and attentiveness to safety and efficiency during wiring projects, ensuring compliance with safety standards and effectively handling complexities like outdated knob-and-tube wiring.

2. Factor It Into Your Budget

Full rewiring can be a major cost—but it’s often worth it for safety and resale value. Rewiring the entire house ensures compliance with current electrical codes and provides peace of mind with updated safety features. You may also be able to negotiate the cost with the seller.

3. Check with Your Insurance

Before closing, confirm with your insurance provider whether they’ll cover a home with K&T wiring—and what conditions might apply.

Fixing Knob and Tube Wiring

If you have knob and tube wiring in your home, it may be worth considering fixing it rather than replacing it. However, this can be a complex and time-consuming process, and it may not be worth the cost. In this section, we will explore some of the steps involved in fixing knob and tube wiring.

Older Homes, Modern Peace of Mind

At Century 21 Circa 72, we love the history and character that older New England homes offer—but we also want our clients to feel safe and confident in their investments. If you’re considering a home that might have knob and tube wiring, our team is here to guide you through the process, connect you with trusted inspectors, and help you make an informed decision.

Have questions about buying or selling older homes in Concord or across New Hampshire?We’re always just a call away.

📍 46 Pleasant Street, Concord, NH📞 603-224-3377✉️ info@c21nh.com