How to Replace Knob and Tube Wiring

Introduction

Knob and tube wiring was commonly installed in homes built before 1950. This old type of electrical wiring can be dangerous due to lack of grounding, overloaded circuits, and deterioration of insulation over time. Replacing knob and tube wiring with modern wiring greatly improves electrical safety. This article provides a complete, in-depth guide on how to replace knob and tube wiring yourself.

Dangers of Knob and Tube Wiring

Knob and tube wiring has three main dangers that make replacement necessary:

Lack of Grounding

• Knob and tube circuits have no ground wire. This makes them more prone to electrical shocks and fires.
• Modern wiring systems have a ground wire that divert stray electrical current away from people and flammable materials.

Overloaded Circuits

• Knob and tube wiring was designed for lower electrical loads than we use today.
• Running too many appliances on old wiring can lead to overheating and fire hazards.

Deteriorating Insulation

• The insulating material on knob and tube wires becomes brittle and cracks over time.
• This allows wires to touch each other or grounded materials, again raising fire and shock risks.

When to Replace Knob and Tube Wiring

Here are some signs it's time to replace knob and tube wiring:

• Frequent tripped circuit breakers or blown fuses from overloaded circuits
• Discolored or warm outlets and switches indicating overheating
• Home inspection identifies knob and tube wiring
• Visible cracks or wear on wire insulation
• Experiencing frequent electrical shocks from appliances and fixtures
• Light fixtures dimming or flickering from inadequate power delivery

Safety should be the #1 consideration in maintaining old electrical systems. It's smart to replace knob and tube wiring before problems arise.

Preparing for the Replacement Project

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

Hire a Licensed Electrician

• Only licensed electricians should take on such major electrical work.
• They have the skills, knowledge and tools to complete the job safely.

Get Required Permits

• Most areas require permits for rewiring projects. An electrician can handle this.

Have Utilities Shut Off

• Notify your electrical utility company to shut off power during the wiring replacement.

Remove or Protect Belongings

• Remove furniture and other items from the rewiring areas.
• Use sheets and tarps to protect belongings from dust and debris.

Replacing Knob and Tube Wiring: Step-by-Step

With proper planning and safety precautions, a licensed electrician can methodically replace knob and tube wiring:

1. Turn Off Electrical Power

• Have utilities disconnect power to the house before starting.
• Test circuits with a voltage tester to be sure power is off.

2. Remove Old Wiring

• Access wiring through attics, basements and opened walls/ceilings.
• Carefully disconnect and remove old wiring from outlets, switches and junction boxes.

3. Install New Wiring System

• Run new wires through walls and ceilings to each box and fixture.
• Use safe wiring suited for the appropriate amperages and loads.
• Connect the new grounded circuits properly at main electrical panel.

4. Replace Devices and Fixtures

• Install updated outlets, switches, junction boxes and light fixtures.
• Use materials approved for the new wiring system.

5. Inspect and Test

• Visually inspect to ensure proper installation of new wiring.
• Test all circuits for proper function and use circuit testers to verify grounding.

6. Insulate and Patch

• Insulate inside walls and ceilings to prevent drafts or energy loss.
• Patch openings in walls and ceilings from installation.
• Paint, wallpaper or finish surfaces to match the rest of the room.

Cost to Replace Knob and Tube Wiring

The cost for rewiring a whole house averages $8,000 to $15,000 but can be higher depending on:

• House size and number of circuits
• Accessibility to wiring runs
• Type of replacement wiring installed
• Local electrician labor rates
• Extent of drywall repairs needed

Upgrading electrical service for the home may add $2,000 to $4,000 more to the overall costs.

It's a large investment that greatly improves home safety and functionality for decades to come. Homeowners should view rewiring as a necessary upgrade, like replacing an old roof or HVAC system.

Improved Electrical Safety

Replacing outdated knob and tube wiring with modern wiring provides:

• Fire prevention from tripped breakers and grounded systems
• Shock prevention through proper grounding
• Reliable power flow to all electrical devices and appliances
• Energy efficiency from updated wiring gauges and insulation
• Increased home value by updating outdated and potentially dangerous wiring

Home electrical systems should keep pace with modern needs and safety standards. Taking on the project of rewiring now provides peace of mind that your home's electrical system is safe and sufficient for your family's needs.