“Little-Known Reasons Why Knob and Tube Wiring Still Matters”

What is Knob and Tube Wiring?

Knob and tube (KT) wiring was an early standardized method of electrical wiring used in buildings in the United States from about 1880 to the 1940s. It consists of single insulated copper conductors run within wall cavities, passing through joist and stud drill-holes via protective porcelain insulating tubes, and supported on nylon knobs.

KT wiring has the following key features:

This old wiring system has largely been replaced by modern wiring methods like NM cable or conduit wiring. However, you can still find KT wiring in older homes built before 1950.

Why KT Wiring Still Exists in Older Homes

There are a few reasons why knob and tube wiring persists in some older homes today:

1. It was extremely reliable and well-built

2. Upgrading can be difficult and expensive

3. Safety concerns are often exaggerated

Why KT Wiring is Still a Concern

However, there are also some valid reasons why knob and tube wiring raises safety concerns today:

1. Lack of grounding

2. Insulation breakdown

3. Improper modifications

4. Difficulty obtaining insurance

Weighing the Options for Homes with KT Wiring

If you have knob and tube wiring in your older home, you have a few options:

I would get an assessment from an electrician to identify any problem areas or urgent upgrades needed. They can also give you a rewiring cost estimate.

Consider your budget, plans for renovations, and insurance requirements when deciding your approach. With proper maintenance and limited upgrades, KT wiring can often be left safely in place. But be aware of risks like insulation breakdown and lack of grounding.


While knob and tube wiring is antiquated, it remains present in many older homes due to its durability and the high cost of replacing it. Safety issues arise when it is disturbed or improperly modified. With informed decision making, you can address KT wiring risks while also retaining some of its original circuits. Understanding the pros and cons allows homeowners to make smart choices about maintaining or upgrading this vestige of old electrical systems.