How to Safely Replace Knob-and-Tube Wiring in Older Homes

What is Knob-and-Tube Wiring?

Knob-and-tube wiring was commonly used in homes built before the 1940s. It consists of individual wires that are run through open air, supported by ceramic knobs and tubes.

The wires are generally uninsulated, which can make knob-and-tube wiring dangerous. The wiring is also often brittle and cracked from age, increasing fire and shock risks. Replacing knob-and-tube wiring improves safety and allows for easier electrical upgrades in older homes.

Dangers of Knob-and-Tube Wiring

There are several dangers associated with old knob-and-tube electrical systems:

• Fire hazard - The uninsulated wires used in knob-and-tube systems can overheat or arc and spark, starting electrical fires.

• Shock hazard - Exposed conductors may energize metal components of the house, like radiators or plumbing pipes, increasing the risk of shocks.

• Limitations - It is difficult to increase capacity and number of circuits with knob-and-tube wiring. This can lead to overloaded circuits and the inability to add new appliances and devices.

• Insurance issues - Many insurance companies will not insure homes with knob-and-tube wiring due to the risks.

When to Consider Replacement

Here are some signs that it may be time to replace knob-and-tube wiring:

• You need to increase electrical capacity for a remodel or to add new appliances and devices.

• The wiring shows signs of damage like brittleness, cracks, or burn spots.

• You frequently experience blown fuses or tripped breakers from overloaded circuits.

• Receptacles, switches, or light fixtures feel warm to the touch, a sign of overheating.

• You have experienced unexplained power outages or flickering lights.

• Your home insurance company requires an electrical upgrade.

Preparing for a Rewiring Project

Replacing knob-and-tube wiring is a major project that requires planning and preparation:

• Get quotes - Have a licensed electrician provide a quote for the complete rewiring job. Get multiple quotes for comparison.

• Secure permits - Contact your local building department to learn about permit requirements for rewiring projects.

• Have a plan - Decide how much wiring you want to replace and make a plan for new circuits, outlets, switches and fixtures.

• Protect valuables - Remove artwork, electronics, and other valuables since walls and ceilings will need to be accessed.

• Budget - Factor in costs for materials, labor, and repairs to walls and ceilings. Rewiring a whole house could cost $8,000-$15,000.

Replacement Options

There are a couple options when replacing old knob-and-tube wiring:

Full Rewire

This involves removing all of the old wiring and installing completely new electrical system with modern wiring, breaker panel and grounded outlets.

Pros:

• Safely upgrades entire electrical system
• Allows for adding circuits and capacity
• May increase home value

Cons:

• Very labor intensive and expensive ($10,000 plus in many cases)
• Requires access to all walls, ceilings and floors

Pigtailing

This cheaper alternative involves leaving the old wiring in place but splicing ("pigtailing") grounded Romex cable to extend circuits to devices.

Pros:

• Less invasive than full rewire
• Lower cost

Cons:

• Original wiring remains in place
• Limited capacity increase

Hiring an Electrician

It is highly recommended to hire a licensed electrician rather than attempting DIY knob-and-tube replacement. Here are some tips for hiring an electrician:

• Verify they are properly licensed and insured.

• Ask for references from past wiring jobs.

• Get a detailed quote in writing before work begins.

• Choose an electrician who specializes in old home rewiring.

• Ask lots of questions to understand the scope and approach.

• Agree on a payment schedule with progress payments rather than one lump sum.

Safety Precautions During Rewiring

Replacing knob-and-tube wiring requires making modifications to your home's electrical system. Safety should be the number one priority.

• Turn off power at the main breaker before starting. Verify it is off!

• Test wires before touching to ensure power is off.

• Keep work areas clean and safe.

• Follow all electrical codes and safety procedures.

• Use fire resistant materials when sealing penetrations in walls.

• Keep children and pets away from work areas.

By following safety protocols, you can ensure the knob-and-tube replacement process goes smoothly and safely. Consult with your electrician if you have any concerns.

Completing the Project

Once the new wiring is installed, there are a few final steps:

• The electrician should test all circuits to verify proper operation.

• Apply for final inspection from the building department when work is complete.

• Update home insurance once wiring is replaced and inspected.

• Add new circuits to your electrical panel labeling.

• Repair any walls, floors, and ceilings damaged during installation.

• Dispose of old wiring properly at a construction waste facility.

Replacing hazardous knob-and-tube wiring requires time and commitment. But improving electrical safety in an older home is well worth the investment. Follow the steps outlined and work closely with an experienced electrician to complete a successful upgrade project.