Rewiring a home with old knob-and-tube wiring can be a dangerous endeavor for the inexperienced DIYer. Knob-and-tube wiring was commonly installed in homes built before 1950 and has become outdated and hazardous. Working with live electrical wires always carries risks, but knob-and-tube wiring poses particular hidden dangers that homeowners should understand before attempting a rewiring project. This guide will walk you through the key steps to rewire your vintage home safely.
Dangers of Knob-and-Tube Wiring
Knob-and-tube wiring consists of individual wires that are not bundled together like modern electrical cables. The wires are supported along their length by ceramic knobs and pass through hollow tubes at intervals. While this type of wiring was considered safe and reliable when first introduced, it does not meet modern electrical code requirements for a few important reasons:
The insulation on old knob-and-tube wires becomes brittle over time, leading to cracks and exposure of the copper wire inside. This creates a serious fire hazard. Exposed wires can overheat or arc to adjacent wires or metal surfaces.
Proper grounding was not part of the original knob-and-tube standards. Ungrounded circuits cannot safely handle high-wattage appliances, and make GFCI outlets impossible to install.
The capacity of knob-and-tube circuits is often insufficient for modern households. Overloaded wires pose overheating and fire risks.
Dangers of DIY Rewiring
While rewiring an old home is a smart idea, it can also be dangerous if proper precautions are not taken:
Shutting off the main breaker does not guarantee knob-and-tube wires are dead. They can be spliced into other circuitry further down the line that remains live. Accidentally contacting live wires can result in severe electrical shock or death.
Knob-and-tube wires are often hidden behind walls, ceilings, and insulation. Drilling or cutting into hidden, live wires can be catastrophic.
Working in tight attic or crawl space areas with limited visibility and awkward access increases chances of electrical contact accidents during wiring work.
Understanding circuit mapping, making proper new connections, and meeting code requirements are complex tasks. Mistakes can leave dangerously faulty wiring.
How to Rewire Safely
Rewiring knob-and-tube circuits can be done safely by following key guidelines:
Turn Off Power
The first step is to turn off all main breakers and verify power is off to all circuits, even those not intended to be rewired. Check with a non-contact voltage tester.
Identify All Wiring
Carefully locate the path of all knob-and-tube circuits within walls, attics, basements so you know what to expect when demolishing. Use an inspection camera for hidden wires.
Remove Old Wiring
Once all wiring is mapped, remove the old knob-and-tube wires in their entirety so they do not interact with new wiring. Capping off is not sufficient.
When demolishing, work carefully to avoid hidden wires. Be vigilant when using tools or drilling. Wear electrical gloves and eye protection.
Hire a Licensed Electrician
Consider hiring a licensed electrician if the rewiring is extensive. They have the expertise to do the job safely. Some home insurance policies also require licensed electricians for electrical work.
Install New Wiring
Replace old wiring with new cables that meet NEC requirements. Use appropriate wire gauges and certified materials. Follow local building codes closely.
Ensure Grounding & GFCIs
New wires and circuits must be properly grounded. Install GFCI outlets anywhere wiring is near water sources. This provides important shock protection.
Label New Circuits
Label each new circuit clearly in the service panel. This avoids confusion about what each circuit controls and overloading.
Inspect Completed Work
Do not restore walls or insulation until all work can be inspected for safety and code compliance. Check for proper wire connections, grounding, and no exposed wires.
Rewiring a home with knob-and-tube safely is absolutely possible for a diligent DIYer. Paying close attention to each step and following safety procedures is crucial when dealing with hazardous old wiring. For large or complicated rewiring jobs, hiring a professional electrician is highly recommended. They have the training and experience to avoid the hidden dangers of knob-and-tube. With careful planning and precaution, you can restore the electrical system in your vintage home and gain much-needed safety and capacity.