I still remember the first time I saw knob and tube wiring in an old home. The ceramic knobs and cloth-covered wiring running through the walls and attic were like something from another era. Little did I know then how that antiquated electrical system would shape my career and spark years of controversy in the electrical industry.

In this article, I will take a deep dive into the rise and fall of knob and tube wiring. We will explore how it became the standard for decades, then was made obsolete virtually overnight. The intense debates between electricians and home inspectors over this old technology changed how we look at electrical safety. Join me as we uncover the hidden history of knob and tube wiring and how it transformed electrical standards forever.

The Rise of Knob and Tube Wiring

Back in the late 1800s and early 1900s, knob and tube wiring rapidly became the standard for electrical systems in American homes. Here's a quick background on this now obsolete technology:

During the early 20th century, as electricity became commonplace in homes, knob and tube offered a cost-effective way to add wiring. The asbestos insulation and spaced out wires prevented fires. By the 1930s, it was the wiring method for nearly all homes. But after WWII, a new alternative would emerge and ignite controversy.

The Rise of Romex Wiring

After World War II, new types of plastic insulated wires became widely available. The most popular was Romex cable - a flexible plastic sheathed cable containing three insulated copper wires.

Romex offered major advantages over old-fashioned knob and tube:

By the 1950s, Romex had become the new standard for home wiring. It was easier to install, safer, and could handle more power. Yet knob and tube refused to completely die off.

The Slow Phase Out of Obsolete Knob and Tube

Even after Romex wiring became dominant, knob and tube systems continued to age in place in existing homes. For homeowners, fully rewiring with Romex was expensive. As long as the decades-old systems seemed to work, many saw no reason to replace them.

Yet problems gradually emerged, including:

By the 1970s, knob and tube was clearly outdated and even dangerous. But many homeowners resisted swapping it out due to the high costs of full rewiring.

This set the stage for an ongoing clash between electricians recommending upgrades, and frustrated homeowners hoping to keep their existing systems.

The Brewing Controversy Between Electricians and Home Inspectors

As knob and tube wiring aged far beyond its expected lifespan, tensions rose between electricians and home inspectors over how to handle it.

There were good faith arguments on both sides:

This dispute over knob and tube has sparked heated debates for decades and still continues today. Home inspectors came under fire for passing systems that electricians insisted were too hazardous to remain in service.

But full rewiring costs often exceeded $10,000, presenting a huge obstacle for home buyers. This difficult issue would eventually force electrical standards upgrades.

How Knob and Tube Wiring Forced Changes to Electrical Codes

The intractable disagreements over knob and tube wiring demonstrated that electrical codes were inadequate. Standards and enforcement were needed to address several problems:

To remedy this, major upgrades were made to electrical codes:

These code changes significantly accelerated the retirement of old knob and tube wiring. What was once commonplace decades ago is now definitively illegal and prohibited in most applications.

Knob and Tube Wiring Today

While it once wired millions of American homes, true knob and tube wiring is now practically extinct:

Yet even after fading into obscurity, knob and tube has left a lasting legacy.

This antiquated wiring system forced us to seriously rethink electrical safety standards. The difficult transition away from knob and tube sparked heated debates, but ultimately improved codes and enforcement. The public is safer today because of the upgrades made necessary by knob and tube wiring.

We now have the perspective of history to see this obsolete system as an evolutionary step toward better electrical safety. While knob and tube wiring is now a relic of the past, the progress it spurred will continue benefiting homes for generations to come.