How to Safely Replace Knob and Tube Wiring

What is Knob and Tube Wiring?

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

This old system has many safety hazards compared to modern electrical wiring methods. The insulation on the wiring can deteriorate over time, exposing live wires. The wires are often spliced together in unsafe ways. The system lacks a proper ground wire, increasing the risk of shocks. Fires can start where wires come into contact with combustible materials inside walls.

Dangers of Knob and Tube Wiring

As a homeowner with knob and tube wiring, I am very concerned about the safety risks, including:

• Fire hazard - The old brittle insulation can crack or peel back, allowing wires to arc and overheat. This can ignite fires in walls and attics.

• Shock hazard - Without a ground wire, knob and tube wiring systems cannot safely handle faults or shorts. Anyone who touches an electrified metal component can get a dangerous shock.

• Overload - The wiring is not designed to handle the power demands of modern appliances and electronics. Connecting too many devices to the wiring can lead to overheating and fire.

• Concealed splices - It was common practice to splice wires together in unsafe ways within walls, hidden from view. This leads to hot spots and fire risks.

• Damage - The wiring becomes brittle with age and is prone to damage from vibrations, rodents, and contact with building materials. Damaged insulation exposes live conductors.

Dangers of DIY Repairs

I certainly do not recommend trying to repair or replace knob and tube wiring yourself, as that could be extremely hazardous. Here are some of the key dangers:

• Electrocution - Working on live wiring without proper precautions and training puts you at serious risk of electrocution.

• Fire - Mistakes during DIY electrical work often lead to electrical fires that can burn down your home.

• You may not fully uncover all the old wiring or make improper connections.

• Insurance issues - Your insurance company may refuse to cover any damage if they determine it was caused by improper electrical work.

• Liability - You can be held legally and financially responsible for any injuries or damage.

Safely Upgrading Knob and Tube Wiring

The only true solution is to have the knob and tube wiring replaced entirely by a licensed electrician. This is the safest approach I highly recommend. The key steps would include:

Finding a Reputable Electrician

• Get referrals and check reviews. Verify licenses and insurance.
• Get multiple quotes for the project scope.
• Ask about their specific experience with knob and tube rewiring.

Inspection and Planning

• Have the electrician do a full inspection of all existing wiring.
• Plan the new wiring routes and circuit layouts.
• Get all necessary permits and have the power company scheduled.

Removal and New Wiring

• Electrician will disconnect all power and remove all old wiring.
• New wiring will be run through non-flammable plastic/metal conduits.
• All junction boxes and devices will be replaced.
• A new electrical panel will be installed.

Restoration and Repairs

• Walls/ceilings will be repaired and restored after new wiring is installed.
• The electrician should handle any drywall, plastering, painting, etc.

Safety Checks and Approval

• Electrical work will be inspected by the local building department.
• The electrician will verify grounding, polarity, and insulation.
• Any problems will be corrected before approval.

Costs of Replacing Knob and Tube Wiring

Rewiring an entire home with knob and tube wiring can cost $8,000 to $15,000 on average. Factors affecting the costs include:

• Size and layout of the home
• Accessibility to routing new wires
• Need for wall/ceiling repairs afterwards
• Your location (labor costs)
• Any special needs like permitting

Partial rewiring of some rooms or circuits can cost $2,000 to $5,000. I recommend setting aside 15% extra for any unforeseen issues during the electrical work. Get quotes from multiple electricians to find a fair price.

While expensive, rewiring will improve electrical safety and allow you to power modern devices. It can also increase your home's value significantly. Your home insurance rates may also go down.

Home Insurance Issues

Most insurance companies will not insure homes with knob and tube wiring due to the substantial fire risks. Exceptions are sometimes made if:

• An electrician verifies the wiring is still in good condition
• The wiring has been deactivated and is no longer in use
• No major claims have been made on the policy

However, policies with exceptions like this often have higher premiums or limitations on liability coverage. Sometimes the insurance company will require repairs within a set timeframe in order to maintain coverage.

So in most cases, it is wise to proactively upgrade the wiring in order to obtain normal rates and coverage. Discuss this issue with your insurance agent.

Electrical Permit Requirements

In most jurisdictions, you will need a permit for replacing knob and tube wiring, which requires passing inspections. The steps usually include:

• Filling out an application with the town building department
• Providing required details about the scope of work
• Paying the permit fee (often based on number of circuits)

The electrician will then need to:

• Schedule rough-in and final inspections
• Make any corrections noted during inspections
• Get final approval after completion

Permits help ensure the work meets the National Electrical Code. Failing to get a permit can risk fines, insurance problems, and issues when selling the home.

In Conclusion

Given the substantial fire and shock dangers of old knob and tube wiring, I highly recommend hiring a professional electrician to replace it completely.

While expensive, rewiring will provide much improved electrical safety and reliability. Make sure to get your insurance company and local permit office involved early in the process. With the proper planning and licensed electrician, you can successfully upgrade this outdated and hazardous wiring in your home.