The Forgotten Knob-and-Tube Wiring That Could Burn Down Your House

What is Knob-and-Tube Wiring?

Knob-and-tube 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 along their length on nailed-down porcelain knob insulators.

This old wiring system has largely been replaced with modern systems using plastic insulated cables and conduits. However, there are still many homes that contain original, hidden knob-and-tube wiring which can be a fire hazard if not properly maintained or updated.

Why Knob-and-Tube Wiring is a Fire Hazard

There are a few key reasons why knob-and-tube wiring can be dangerous:

• No grounding - Knob-and-tube systems were not grounded, making them more susceptible to short circuits and shock hazards. Modern wiring standards require effective grounding.

• Insulation breakdown - The old rubber and cloth insulation on knob-and-tube wires becomes brittle and cracked over time, leading to exposed live wires coming into contact with flammable materials inside walls.

• Overloaded circuits - Knob-and-tube wiring was not designed to handle the higher wattage load of modern appliances and devices. Overheating of wires is a fire risk.

• Exposed splices - Splicing of knob-and-tube wires was done by twisting wires together with electrical tape, which can come undone over time and cause sparks.

• Inaccessible wiring - It runs through inaccessible wall cavities, making it hard to inspect and replace damaged wiring before sparks and fire can occur.

Warning Signs of Knob-and-Tube Wiring

There are some clues that may indicate your older home still contains obsolete and dangerous knob-and-tube electrical wiring:

• Two-prong ungrounded outlets
• Blown fuses from minor appliance use
• Older light fixtures where wires enter through the ceiling
• Mismatched wiring colors compared to modern standards
• Seeing actual porcelain knobs or tubes inside walls
• Wiring running through drilled holes in joists and studs

If in doubt, have an electrician inspect your home's wiring to identify if knob-and-tube circuits are present. Do not take chances with aged electrical systems.

Dangers and Consequences of Old Wiring

Failing to replace antiquated knob-and-tube wiring poses serious risks:

• Electrical fires - Short circuits in old brittle wiring can ignite flammable materials inside walls. Fires can spread quickly through inaccessible spaces.

• Shocks and electrocution - Exposure of bare wiring creates shock risks. Lack of grounding removes an important safety backup.

• Insurance issues - Most insurers will not cover homes with knob-and-tube wiring, or charge higher premiums. Policies may be canceled.

• Difficulty selling property - Homebuyers are unlikely to purchase a property containing this outdated fire-prone wiring, unless it is replaced.

• Loss of life and property - Electrical fires kill hundreds of people per year and cause billions in property damage. Don't let obsolete wiring put your family at risk.

Recommendations for Homeowners

If you have old knob-and-tube wiring, the safest solution is to have it fully replaced by a licensed electrician with modern wiring meeting current code standards. Other recommendations include:

• Never attempt to repair or modify knob-and-tube wiring yourself
• Use surge protectors on old circuits and avoid overloading with too many appliances
• Have an electrician install GFCI outlets on ungrounded circuits for added protection
• Don't run extension cords or power strips on old wiring
• Check wiring before any remodeling work and when renovating older homes
• Install smoke alarms and AFCIs (arc-fault circuit interrupters)
• Consult professionals to understand all upgrade options and costs

Replacing hazardous old electrical wiring greatly reduces fire risks and gives homeowners peace of mind. Don't let outdated knob-and-tube wiring put your most valuable assets - your family and home - in danger.