Introduction
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:
- Invented in the 1880s - Knob and tube consisted of single black rubber insulated wires supported by ceramic knobs and tubes.
- No ground wire - Unlike modern systems, knob and tube had no ground wire and no protection from short circuits.
- Air insulated - The wires were separated by air space to prevent sparks and insulation breakdown.
- Labor intensive - It required a lot of skill as each wire had to be routed through walls and ceilings by hand.
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:
- Faster installation - Romex could be quickly pulled through walls vs routing each wire separately.
- Includes ground wire - Romex introduced a bare copper ground wire for protection from shorts.
- Plastic insulation - The plastic coating was more durable and safer than the old cloth insulation.
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:
- Unsafe lack of grounding - No protection from short circuits.
- Fire hazards - Brittle, cracked insulation on old wires.
- Inadequate for modern loads - Low capacity for major appliances.
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.
- Electricians pushed for upgrades - They saw too many hazards to leave old systems in place.
- Inspectors were more flexible - They argued that functioning knob and tube could be left alone.
There were good faith arguments on both sides:
- Electricians prioritized safety, and wanted to completely eliminate fire risks.
- Inspectors wanted to avoid burdening buyers with major expensive upgrades.
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:
- Ambiguity - The codes lacked clarity on if or when knob and tube systems must be replaced.
- Obsolescence - Continuing to permit extremely outdated and hazardous wiring was unacceptable.
- Inconsistency - Different jurisdictions took different approaches, leading to confusion.
To remedy this, major upgrades were made to electrical codes:
- Removal requirements - New codes mandated full knob and tube replacement in many cases.
- Restrictions on modifications - It became difficult to upgrade other systems like plumbing without also upgrading wiring.
- Improved enforcement - Mandatory inspections ensured that code violations were identified.
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:
- Virtually no working systems remain beyond isolated rural cases.
- Completely obsolete technology that no reputable electrician would install today.
- Modern electrical codes essentially ban knob and tube systems.
- Any remaining original knob and tube wiring requires full replacement.
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.