How to Rewire Your Home With Knob and Tube Wiring

What is Knob and Tube Wiring?

Knob and tube wiring was commonly installed in homes built before the 1940s. It gets its name from the porcelain knobs that insulate the wires, and the tubes that surround the wires where they pass through framing members.

Key characteristics of knob and tube wiring:

Two separate wires, one for the hot and one for the neutral, run through air spaces in walls and ceilings
Wires are supported by porcelain knobs and run through ceramic tubes where they pass through framing
No ground wire, just hot and neutral
Wires have cloth or rubber insulation that can become brittle with age
Limited amperage - not designed to handle demands of modern homes

While knob and tube wiring was suitable for lighting and small appliances used in the early 20th century, it does not meet the needs of modern homes. The lack of grounding and aging insulation can present safety hazards like electrical fires and shocks.

Dangers of Knob and Tube Wiring

While knob and tube wiring may have worked fine for the first half of the 20th century, it can be very dangerous by modern standards. Here are some of the main risks:

Fire hazard - the old insulation becomes brittle and cracks over time, exposing the wire to potential shorts. This can lead to overheating and electrical fires.
Shock hazard - with no ground wire, there is an increased risk of getting shocked from touching a faulty appliance.
Insufficient amperage - knob and tube wiring typically provides only 30-60 amps to the entire house. This is not enough to run major appliances like air conditioners, electric stoves and clothes dryers.
Insurance issues - many insurance companies will not insure a home with knob and tube wiring due to the fire risk.

Any of these hazards make it important to consider upgrading the wiring in a home with knob and tube.

Why Rewire with Modern Wiring?

Given the safety issues, most electricians recommend fully rewiring homes that still have knob and tube wiring. Here are the main advantages of rewiring with modern wiring:

Prevent fires - modern wiring has up-to-date insulation that won't crack and expose wires. This greatly reduces fire risks.
Safety - modern wiring includes a ground conductor, providing protection from shocks.
Higher capacity - modern wiring can safely provide 150-200 amps for all your home's electrical needs.
Convenience - you can safely use any modern appliances and devices when rewired. No more blown fuses from vacuum cleaners!
Insurance - upgrading the wiring allows you to get insurance for your home.
Increase property value - rewiring is an investment that increases your home's value.

Overall, rewiring provides much needed safety and convenience for older homes. The costs involved are well worthwhile for most homeowners.

Preparing for a Rewiring Project

Rewiring an entire home is a major project that requires planning and preparation. Here are some key steps to take before starting:

Find an electrician - only licensed electricians should handle home rewiring projects. Get quotes from 3-4 local electricians.
Get permits - your electrician will need to pull the proper permits before starting work.
Decide on wiring method - discuss options like armored cable vs conduit with your electrician.
Consider any upgrades - it's a good time to add circuits, outlets, switches and fixtures.
Make a plan - come up with a room-by-room plan for running wires with your electrician.
Budget - factor in materials, labor and permits. Rewiring a whole home often costs $8,000-$15,000.
Protect valuables - remove art, electronics and fragile valuables before work begins.
Find temporary housing - you may need to move out during the rewiring project.

With proper planning and preparation, your rewiring project is more likely to go smoothly.

How Does a Home Rewiring Project Work?

The process of fully rewiring a home involves:

Removal of old wiring - The electrician will remove all the old knob and tube wiring. This includes disconnecting wires from outlets, switches and light fixtures. The knobs and tubes are taken out of the walls.
Running new wires - Modern wires are run through the walls and ceilings of the home. The electrician will drill small holes to route the new wires between outlets, switches and fixtures.
Installing electrical boxes - Old work boxes are installed to hold the wires at each outlet, switch and junction point. Armored cables and conduits connect everything.
Connecting devices - Your outlets, light switches, lighting fixtures and appliances get connected to the new wiring system.
Inspection - The work will be inspected to ensure it meets national and local electrical codes.

The process involves some demolition and building back up of your home's electrical system. With an experienced electrician, the workflow is carefully planned out so your home retains power during the transition to the new wiring system.

Common Wiring Methods for Rewires

Electricians have two main options when rewiring a home - armored cable (AC) or electrical conduit:

Armored cable - Also called BX or MC cable, this flexible cable houses the insulated wires in a spiral wound metal covering. It is run through walls and ceilings and offers good physical protection.
Conduit - Rigid metal or PVC tubing that protects wires routed through. More durable but requires more labor to install.

Discuss the pros and cons of each method with your electrician to decide what is best for your particular rewiring project.

Safety Tips During a Rewiring Project

When undertaking a major rewiring project, it is important to keep safety top of mind:

Turn off power - The main breaker should remain shut off except when necessary for testing.
Keep clear of work areas - Do not enter any rooms or spaces where the electrician is working.
Store tools/materials safely - Do not allow children or pets access, as they could be hazardous.
Prevent falls - Use caution on ladders, scaffolding and access areas.
Ventilate properly - Ensure good airflow when work generates dust or fumes.
Get inspections - Thoroughly check work at each stage to catch any issues early.
Use GFCIs - These special outlets provide protection against shocks and should be used during construction.

Staying safe requires everyone working together. Be sure to communicate any concerns with your electrician as well.

Questions to Ask Your Electrician

When hiring an electrician for your rewiring project, here are some key questions to ask:

Are you licensed, insured and bonded?
How much experience do you have with rewiring old homes?
Will you pull the proper permits for this project?
Do you provide itemized written quotes for materials and labor?
What wiring method do you recommend for my home and why?
How will you ensure the safety of my family during the work?
What is your timeline estimation for completing the rewiring?
How can I prepare my home before work begins?
Will the walls need to be opened up and patched during the rewire?
How much disruption to our living space should we expect?
What is your protocol for inspecting and testing the new wiring?
Do you offer any warranties on your rewiring work?

Taking the time to thoroughly interview electricians will help you find the right pro for the job.

Alternatives to a Full Rewire

While a full rewiring is recommended for most older homes, here are a couple alternatives to consider:

Circuit breaker panel upgrade - Upgrading the main panel provides modern safety features. However, it doesn't address issues with old wiring.
Running new wires - You can run new wires for major appliances without redoing the whole home. Leaves you with a mix of old and new.
Rewiring just problem areas - Target hazardous areas like the kitchen or laundry room for upgrades first.

However, these band-aid fixes still leave much of the old, unsafe wiring in place. Fully rewiring the house provides the most safety and value for your investment.

Conclusion

Rewiring a home with old knob and tube wiring requires weighing safety risks versus the costs involved. For most homeowners, the expense is fully justified by the benefits of modern wiring. With proper planning and a skilled electrician, the project can go smoothly. Taking the time to do it right greatly reduces potential hazards and adds value and convenience to your home for decades to come.