How to Replace Knob and Tube Wiring

Knob and tube wiring was commonly installed in homes built before 1950. This old wiring system has some safety concerns, so many homeowners look to replace it with modern wiring. Replacing knob and tube wiring completely can be a big project, but it will make your home much safer. Here's an in-depth look at everything you need to know to replace knob and tube wiring.

Dangers of Knob and Tube Wiring

Knob and tube wiring gets its name from the ceramic knobs and tubes that insulate the wires. While it was suitable for the lower electricity demands of the early 20th century, knob and tube wiring can be dangerous by today's standards for several reasons:

• Fire hazard - The old, brittle insulation can crack and expose bare wires. This creates a serious fire hazard. Knob and tube wiring lacks a ground wire, which also increases fire risk.

• Overloaded circuits - The wiring is not designed to handle the electricity usage of modern appliances and devices. Overloaded circuits can overheat and spark fires.

• Unsafe modifications - Unqualified DIYers often modify or splice knob and tube wiring in unsafe ways when adding electrical capacity. This dramatically increases fire risk.

• Insurance issues - Many insurance companies will not cover homes with knob and tube wiring, or charge much higher premiums. This makes protecting your investment very difficult.

These safety issues mean it is highly recommended to completely replace knob and tube wiring in any home where it exists.

When to Call an Electrician

Some homeowners want to DIY knob and tube replacement to save on costs. However, there are some cases where you should call a professional electrician:

• If the wiring is in very tight spaces or buried in finished walls and ceilings. Removing knob and tube wiring without damaging your home takes experience.

• If you are not 100% sure you can safely disconnect all power during the project. Working with live power lines is extremely dangerous.

• If the scope of the project is very large, such as rewiring the whole home. This is time consuming and labor intensive.

• If you are uncomfortable working with high voltage electrical systems. It's better to be safe than risk electrocution or burning down your home.

For major rewiring projects, hiring a reputable licensed electrician is highly recommended for safety. But some DIYers can handle replacing an isolated section of knob and tube wiring by following important safety precautions.

DIY Safety Tips

If you take on any DIY electrical work, safety should be your top priority. Follow these tips to avoid getting hurt or damaging your home:

• Turn off power at the main breaker panel - This ensures wires you are working on are fully de-energized to prevent shocks.

• Disconnect the old wiring - Remove fuses, turn off circuits, and confirm wires are not hot before disconnecting knob and tube wires.

• Work with a partner - Have someone available to call 911 in an emergency.

• Wear personal protective equipment - At minimum, wear safety goggles and gloves when handling electrical wiring.

Proceed with extreme caution. If you have any doubts or feel unsafe, stop work immediately and call an electrician.

Determining the Scope

The first step for any knob and tube replacement project is to determine the scope of wiring that needs to be updated.

• Inspect the attic and basement - Look for the old wiring and how far it extends.

• Check inside walls - Removing cover plates reveals if knob and tube feeds to switches and outlets.

• Assess what needs rewiring - Focus first on wiring feeding major appliances and high electricity areas.

• Develop a plan - Determine which sections of knob and tube wiring to replace first. Hold off on areas not currently in use.

Taking time to thoroughly assess the scope ensures you tackle the most important electrical risks. It also prevents you from overestimating a DIY project if much of the old wiring is inaccessible without major demolition work.

Removing Knob and Tube Wiring

Once you know which wires need to be replaced, the next step is carefully removing the old knob and tube wiring.

• Label each circuit - Note which fuses or breakers power each section of wiring before disconnecting anything.

• Detach wires from any outlets or fixtures - Screws hold wires to outlets. Push-in connectors attach them inside light fixtures.

• Cut wires coming from walls - Snip wires where they enter through holes into each room.

• Pull wires out of conduits - Fish old wires out of ceramic tubes leaving the tubes in place to re-use.

• Remove knobs - Unscrew any knob fittings attached to framing without letting wires fall into walls.

• Keep wires intact as much as possible - Avoid cutting wires in attics and basements until ready to pull them out completely.

Removing knob and tube wires is tedious work, but necessary to make room for new wiring.

Running Updated Wiring

Modern electrical wire comes in 2 common types:

• Non-metallic (NM) cable - This flexible cable has insulated wires bundled together inside a plastic sheath. It is easy to fish through walls.

• Armored cable - This is similar to NM cable but with an external metal covering for more protection. It is less flexible so harder to install.

For most homes, NM cable is perfectly suitable for replacing old wiring. Select the gauge (wire thickness) recommended for the circuits you are installing.

Follow these steps to run new wiring:

• Plan routes accessible from above or below - Map out paths to feed replacement wiring to each location. Attics and basements provide access.

• Fish cables through walls - Use long flexible fiberglass rods to push new cables through openings left by old knob and tube removal.

• Staple cables in place - Use insulated staples to secure cables every few feet through attics, basements, and crawl spaces.

• Label both ends of each cable - Use numbered tags to identify which cables correspond to which circuits for easy reconnection.

• Connect new wires to fixtures - Secure cables to outlets and switches using screw terminals or push-in connectors.

Take things slowly and methodically to avoid leaving loose wires or making dangerous connections.

Reconnecting Devices and Fixtures

Once new wiring cables are in place, you can start reconnecting devices like outlets, switches, and light fixtures.

• Confirm no stray strands are loose - Check that wire connectors are tight with no loose strands that could cause shorts.

• Match wire colors - Connect black (hot), white (neutral), and green/bare ground wires correctly.

• Secure connections - Wrap wires clockwise around screws and tighten firmly or push all the way into connectors.

• Reinstall cover plates - Put light switches and outlet covers back on to prevent accidental contact with wires.

• Test each device - Turn power back on at the main panel and test that all lights, switches, and outlets function properly.

Go slowly and double check all devices to make sure new connections are solid. Report any non-working fixtures to an electrician in case the wiring needs troubleshooting.

Important Next Steps

After you replace sections of knob and tube wiring, there are a few important next steps:

• Add GFCI outlets - Improve protection against shocks by replacing plain outlets with ground fault circuit interrupter outlets. Test them monthly.

• Leave accessible parts intact - If old wiring still feeds other areas, leave it disconnected but in place for future projects.

• Insulate exposed wiring - Wrap any visible knob and tube wires with electrical tape so they do not pose a shock risk.

• Have an electrician inspect - Hire a pro to validate your DIY wiring replacement was done properly and safely.

• Update home insurance - Notify your agent that knob and tube wiring has been replaced to get lower insurance premiums.

Proper follow-up ensures your knob and tube replacement project improves the safety of your electrical system.

Hiring a Professional Electrician

For large knob and tube rewiring projects, the best option is hiring a professional electrician. Although it costs more upfront, there are several benefits:

• Safety - Licensed electricians are fully trained to safely replace old wiring. They follow the proper procedures to avoid electrical hazards.

• Expertise - Electricians have years of daily hands-on experience you can't get from reading DIY guides. They know all the tricks to remove old wiring and install new wiring efficiently.

• Latest codes - Professional electricians always incorporate the most current electrical codes and standards into their work. This ensures optimal safety and legality.

• Problem solving skills - Electricians have seen thousands of unique wiring scenarios. They know how to approach unusual situations and troubleshoot issues.

• Warranties - Many electricians offer warranties on their electrical work. This protects against defects and gives you peace of mind.

Although hiring an electrician costs more up front, it is worth it for large knob and tube rewiring projects to ensure a safe electrical system. Carefully check reviews and licenses to find a reputable local professional electrician you trust to get the job done right.