How to Replace Knob and Tube Wiring

What is Knob and Tube Wiring?

Knob and tube (K&T) 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 or ceiling cavities, passing through joist and stud drill-holes via protective porcelain insulating tubes, and supported on nailed-down porcelain knob insulators.

K&T wiring has largely been replaced with modern electrical cables and conduits due to safety concerns and the difficulties of installing modern devices on the system. However, some older homes still rely on K&T wiring. Replacing this outdated system can provide much-needed safety and functionality upgrades.

Dangers and Drawbacks of Knob and Tube Wiring

There are several key reasons to replace K&T wiring:

• Fire hazard: K&T wiring lacks grounding and has brittle insulation that can crack over time. This can lead to arcing, sparks, and potential fires.

• Overloading: K&T wiring was not designed to handle the electricity demands of modern appliances and devices. Overloading the system can cause dangerous overheating.

• Difficult to update: It is challenging to splice into K&T wiring to add outlets, lighting, or other upgrades. Attempting DIY upgrades often leads to improper connections.

• Insurance issues: Many insurance companies will not insure homes with K&T wiring due to the fire risk, or will require an expensive rider.

• Resale value: K&T wiring can make it difficult to sell a home and may scare away potential buyers.

Replacing this outdated and potentially dangerous wiring is a smart investment in safety, functionality, insurance, and resale value.

Preparing for a K&T Wiring Replacement Project

Before beginning a full K&T rewire, there are a few key steps to take:

• Consult an electrician: Have a licensed electrician assess your K&T wiring and provide a project quote. They can identify any particularly concerning areas.

• Check with insurance: Inform your insurance company of your plans to replace K&T wiring. They may have requirements for the project.

• Consider electrical load: Make a list of all current appliances and devices in the home. This will help determine the electrical capacity required from the new system.

• Develop a plan: Decide whether to fully rewire the entire home or just replace certain circuits. This will impact the project scope and costs.

• Handle permits: Building permits are usually required for rewiring projects. The electrician can handle this process.

• Prepare the space: Remove furnishings and belongings from work areas. This will provide clear access for the electricians.

Proper planning makes a smooth K&T rewiring project more likely. Rushing into the project can result in overlooked issues and sloppy work.

K&T Wiring Replacement Process

The general process for replacing K&T wiring involves:

Step 1: Turn Off Electricity and Install New Components

The electrician will:

• Shut off main breaker to disable all power
• Install new electrical panel if needed to support added circuits
• Run new wiring from panel to outlets, switches, and fixtures

Step 2: Remove Old K&T Wiring

With power off, the old wiring can be safely removed:

• Carefully pull conductors out of walls and ceilings
• Caution: Avoid leaving wire fragments behind
• Remove old porcelain knobs and tubes
• Patch drill holes

Step 3: Connect New Wiring to Components

The electrician will:

• Connect new wires to outlets, switches, and fixtures
• Ensure grounding meets modern safety codes
• Install GFCI outlets in bathrooms, kitchen, exterior, and damp areas

Step 4: Insulate and Patch

• Pack new insulation around wiring runs
• Patch walls and refinish ceilings
• Paint, wallpaper, and refinish surfaces

With the new wiring installed, inspected, and concealed, the K&T replacement process is complete!

Cost to Replace Knob and Tube Wiring

The costs for a K&T wiring replacement depend on factors like:

• House size
• Number of circuits
• Accessibility of wiring runs
• Local electrician rates

According to HomeAdvisor, the average cost to replace K&T wiring ranges from $8 to $15 per linear foot, with most homeowners paying between $4,000 and $12,000 total. Upgrading the electrical panel or service entrance wires can add $1,000 to $3,000.

Getting quotes from at least 3 local electricians is the best way to estimate the investment for your specific K&T replacement project.

Is It Mandatory to Replace Knob and Tube Wiring?

There is no nationwide code that requires homeowners to replace K&T wiring. However, many local jurisdictions prohibit K&T and require upgrades during remodeling projects or home sales.

Even if not legally mandatory, replacing K&T wiring is an advisable safety upgrade. Any home insurance, sale, or financing contingencies related to K&T wiring are additional reasons to make this wiring replacement investment.

Conclusion

While rewiring an entire home is a major project, it is a worthwhile investment for homes still relying on outdated and dangerous K&T wiring.

Careful planning, hiring a professional electrician, and following safety procedures will result in a smooth wiring replacement process. The end result will be a home with modern wiring that provides essential safety, full electrical capacity, and functionality for decades to come.