How to Safely Replace Knob and Tube Wiring in Your Home

What is Knob and Tube Wiring?

Knob and tube wiring was commonly installed in homes built before the 1950s. It consists of individual hot and neutral wires that are separated from each other, rather than bundled together like modern electrical wiring.

The hot wire is insulated and supported by ceramic knobs, while the neutral wire is suspended in air on porcelain tubes. This type of wiring does not include a ground wire.

While knob and tube wiring was suitable for the time when it was installed, it can be unsafe by today's electrical standards due to the lack of a ground wire and insulation that has degraded over time.

Dangers of Knob and Tube Wiring

There are several dangers associated with old knob and tube wiring:

• Fire hazard - The insulation on knob and tube wires becomes brittle and cracks over time, exposing bare wires that can spark and ignite flammable materials in walls. This wiring is especially concerning in older homes that likely have wood lath and plaster walls.

• Shocks and electrocution - Without a ground wire, knob and tube systems cannot safely handle faults or short circuits. This increases the risk of shocks and electrocution.

• Overloading - Knob and tube wiring was not designed to handle the electricity demands of modern appliances and electronics. Overloaded circuits can overheat and spark fires.

• Insurance issues - Many insurance companies will not issue policies for homes with knob and tube wiring due to the fire risk. Or, they may require expensive ACV (actual cash value) policies instead of standard replacement cost policies.

Signs You Still Have Active Knob and Tube Wiring

Here are some signs that your home likely still has active, live knob and tube wiring:

• You see ceramic knobs and tubes inside walls and ceilings
• Wiring is only two-prong outlets without a ground
• Circuits are only 15 amps
• You have blown fuses rather than tripped breakers
• Older light fixtures are directly wired without junction boxes

If unsure, have an electrician inspect your home's wiring to verify if knob and tube circuits are still in use.

Options for Replacing Knob and Tube Wiring

There are two main options for dealing with knob and tube wiring:

1. Remove and Completely Replace

This is the recommended option for safety. It involves:

• Identifying all locations of knob and tube wiring
• Removing all knob and tube wiring back to the electrical panel
• Installing new wiring meeting modern electrical code
• Installing new outlets, switches, and light fixtures as needed

Pros

• Safely removes old problematic wiring
• Allows rewiring with adequate capacity for modern needs
• May be required by insurance companies

Cons

• Very labor intensive - walls and ceilings need to be opened up
• More expensive than other options

2.pigtailing

This involves leaving the old knob and tube wiring in place but splicing it to new wiring that connects to outlets and fixtures.

• The old wiring is "pigtailed" with new wires that are properly insulated and grounded
• Allows you to avoid removing knob and tube wiring in difficult to access areas

Pros

• Less invasive than fully rewiring
• Lower cost than removing all knob and tube

Cons

• Original wiring is still a fire hazard if degraded
• Does not increase electrical capacity
• May not be approved by insurance companies
• Creates potential "hot spots" at splice points

I do not recommend this shortcut method as it leaves the base fire risk still in place.

Safety Tips When Rewiring a Home Yourself

If you plan to DIY the rewiring work, keep these safety tips in mind:

• Turn off power at the main breaker panel before starting
• Follow local permit and inspection requirements
• Use thick 12 AWG copper wiring for 15 to 20 amp home circuits
• Label all wires to prevent confusion
• Mount new junction boxes securely
• Use wire nuts or connectors properly rated for the wire gauge
• Connect the ground wire to all devices and outlets
• Cover all junction boxes before turning power back on

Rewiring an entire home is complex. Unless you are experienced, it may be safer, faster, and more cost-effective to hire a licensed electrician.

Cost to Professionally Replace Knob and Tube Wiring

The cost to fully replace knob and tube wiring in a home often ranges from $8,000 to $15,000 or more, depending on:

• Home square footage
• Accessibility to wiring runs
• Need for plaster/drywall repair
• Required upgrades to meet current code

Get quotes from licensed electricians to understand the exact costs for your unique situation. Many homeowners find the peace of mind and increased home value are worth the investment.

Replacing hazardous knob and tube wiring greatly improves safety for your home. Follow local building codes, get necessary permits, and consider hiring a professional electrician for this complex project.