I recently purchased my first home, a charming 1920s bungalow. While inspecting the property, I was surprised to learn that segments of the home still contained an obsolete and potentially hazardous type of electrical wiring known as "knob and tube." This discovery prompted me to research this antiquated wiring system to understand the risks it poses.

What is Knob and Tube Wiring?

Knob and tube (K&T) wiring was commonly installed in American homes built before 1950. It consists of insulated copper conductors that are suspended between ceramic knobs attached to the framing studs. The wires are separated from each other by air space rather than being bundled together like modern NM cable.

Some key facts about knob and tube wiring:

While knob and tube was considered a safe and sturdy wiring method in the early 20th century, it lacks most of the safety features required for modern electrical systems.

Why Knob and Tube Wiring is Dangerous

There are several factors that make aging knob and tube wiring a potential fire and shock hazard:

These factors contribute to an elevated fire risk. According to the Consumer Product Safety Commission, nearly 40,000 home fires originating from wiring systems are reported each year in the U.S. Knob and tube wiring likely accounts for a disproportionate share of those fires in older homes.

How Prevalent is Knob and Tube Wiring Today?

It may come as a surprise that a wiring system developed in the late 1800s is still present in millions of modern homes.

Exact statistics are difficult to pinpoint, but some key numbers indicate the widespread prevalence:

So while it has largely faded from use, there is still a very high chance of encountering knob and tube circuits in older homes. Homeowners undertaking renovations often discover previously hidden K&T wiring behind walls and ceilings while doing demolition work.

Dangers and Challenges from Concealed Knob and Tube Wiring

The fact that knob and tube wiring is often concealed and undocumented presents some additional risks and difficulties:

For these reasons, it is advisable for homeowners in older homes to take proactive steps to identify and replace any existing knob and tube wiring during renovations or a pre-sale home inspection.

Is It Possible to Repair or Work Around Knob and Tube Wiring?

Some homeowners attempt limited repairs or develop makeshift solutions to work around knob and tube wiring issues, however this is inadvisable. Some approaches that may seem convenient but are unsafe include:

The only reliable and code-compliant option is fully replacing K&T wiring with new NM electrical cable and adding grounding. Incremental repairs on old wiring simply mask underlying safety issues that will persist.

Is Replacement Necessary Even if Knob and Tube Wiring Appears in Good Condition?

Even if existing knob and tube wiring appears intact and undamaged to the naked eye, replacement is still recommended. There are a few reasons why:

Ideally, knob and tube wiring replacement happens preemptively before any functional failure occurs. This negates the safety issues and provides homeowners with reliable and efficient modern electrical systems.

Does Homeowner's Insurance Cover Replacement Costs?

Since the presence of knob and tube wiring puts the entire property at risk, some insurers will provide funds specifically towards wiring replacement costs as an incentive for the homeowner to upgrade the electrical system.

However, policies and coverage vary widely between providers. Some key considerations are:

Bottom Line - While insurance can offset some costs, homeowners should expect to pay at least part of a knob and tube rewiring project out-of-pocket. But this investment pays dividends in safety.

Just How Expensive is it to Replace Knob and Tube Wiring?

As you might expect, rewiring an entire older home with modern electrical infrastructure is a major undertaking that commands a substantial price tag. Some key factors impacting project costs include:

In terms of ballpark estimates, a full knob and tube rewire for an average 2,000 sq. ft. home often ranges from $8,000 to $15,000. High labor costs in some regions can drive this even higher. Spreading the work over time helps manage costs.

Is a DIY Knob and Tube Wiring Replacement Realistic?

Some competent and experienced homeowners take on DIY wiring projects in their own homes in order to control costs. However, knob and tube replacements have some distinct challenges:

Bottom Line - The complexity and safety considerations inherent to knob and tube replacement make a licensed electrician the only prudent choice for nearly all homeowners. The benefit of experience and accountability outweighs potential savings.

How to Select the Best Electrician for a Knob and Tube Replacement Project

Once the decision is made to hire a professional electrician, take time to identify the best contractor for the job:

Doing diligence ensures the best contractor match and increases the likelihood of a successful wiring overhaul. Don't rush the selection process.

In Conclusion:

While antiquated knob and tube wiring lingers in millions of older homes, it presents a substantial fire and shock risk that only grows over time as insulation deteriorates. Homeowners should educate themselves on identifying these obsolete electrical systems and work towards replacing them completely with modern wiring. The expense can be significant but is a prudent investment in safety. Involving a licensed electrician and your insurance provider helps ease the process. With updated electrical infrastructure, homeowners gain much needed peace of mind knowing their family and property are no longer at risk.