How to Replace Old Knob and Tube Wiring in Your Home
Replacing old knob and tube wiring in your home can seem like a daunting task, but it is doable as a DIY project if you take the proper safety precautions. Knob and tube wiring was an early standardized method of electrical wiring used in buildings in the United States from about 1880 to the 1940s. It consists of insulated copper conductors run through ceramic knobs fastened to framing members, with tubes protecting the wires where they pass through walls and ceilings. While knob and tube wiring has lasted for many decades, it can be hazardous due to lack of grounding, overloading, deterioration, and improper modifications. Replacing it with modern electrical wiring greatly reduces fire and shock risks. This guide will walk you through the key steps I took to successfully replace the old knob and tube wiring in my home.
Things to Know Before Starting
Before diving into the wiring replacement process, there are some important things to understand about knob and tube wiring and the scope of the project:
Knob and Tube Wiring Facts
- Two separate wires, one for hot and one for neutral, rather than a single cable like modern wiring. This means less capacity.
- No ground wire, which is a safety hazard.
- Runs through open air, attached to ceramic knobs and tubes, rather than protected cables. More exposed to damage.
- Often spliced improperly as DIY repairs were made over the decades.
Key Planning Steps
- Check with local permit office - Most areas require permits for rewiring projects.
- Hire an electrician if unfamiliar or uncomfortable with electrical work. Safety should be the top priority.
- Decide how much to rewire - All at once or section by section? The entire house or just problem areas?
- Plan for power outages - Rewiring circuits will require power to be shut off for periods of time.
Safety Gear Needed
- Electrical gloves to protect from shocks
- Eye protection from debris
- Dust mask to avoid breathing dust from drilling into walls
- Hard hat for protection when in crawl spaces or attic
Removing the Old Knob and Tube Wiring
The first step is removing the existing knob and tube wiring. This involves:
1. Turn Off Power and Install New Electrical Panel
- Shut off main breaker to cut all power to the house
- Remove old fuse box or panel and install new breaker panel
This allows you to run new wiring through a modern, safer electrical panel.
2. Remove Visible Knob and Tube Wiring
- Take out any knob and tube running through open areas like the attic, basement, or crawlspaces
- Unscrew or pry off ceramic knobs
- Pull out old individual wires from knobs and tubes
3. Cut Open Walls and Remove Hidden Wiring
- Use a drywall saw to cut openings in finished walls and ceilings
- Locate hidden knob and tube runs and pull out all old wiring you encounter
- This step produces a lot of dust and debris, so wear a mask
Running New Electrical Wiring
Once all the old wiring is removed, I was ready to run new cables:
1. Plan Circuit Map
- Draw up a circuit map indicating new run locations, connections, and circuit breaker assignments
- Plan routes avoiding plumbing pipes, ducts, and other obstructions
2. Drill Holes Between Studs
- Use a long drill bit to bore holes horizontally through studs about one foot apart
- This allows fishing wires between studs inside the walls
3. Fish Wires Through Walls
- Attach a wire fishing tool to the end of a new wire
- Feed through bored holes to route wire neatly through walls and ceilings
- Leave plenty of extra wire at endpoints to make connections
4. Secure Wires to Studs
- Use insulated staples to fasten wiring to wall studs and joists for support
- Keep staples loose enough for wires to slide - no crimping
Follow building codes for proper wire gauge, connection methods, and circuit layouts.
Installing New Outlets, Switches, and Fixtures
The final stage is installing everything to utilize the new wiring:
1. Install New Outlet and Switch Boxes
- Measure and cut drywall to create openings for new boxes
- Secure boxes with screws to studs according to code
- Run wire from boxes to circuit breaker panel connections
2. Connect Wires to Outlets and Switches
- Use wire nuts to connect hot, neutral, and ground wires to outlets and switches
- Attach ground wires to outlet boxes for safety
- Keep different circuits' wires separated in boxes
3. Mount New Outlets, Switches, and Covers
- Attach new outlets and switches into boxes with mounting screws
- Verify grounding with outlet tester before turning circuits on
- Attach new drywall plates and covers to hide boxes and wires
4. Update All Fixtures
- Replace old light fixtures, connecting to new wiring
- Swap out unsafe appliance cords and plugs as needed
- Install GFCI outlets in kitchen, bathrooms, laundry, etc.
Thoroughly check for functioning, grounded circuits before reconnecting the main power.
To complete the project:
- Patch and repaint walls with drywall mud and paint
- Reinstall flooring, trim, and ceiling coverings removed during rewiring
- Caulk around boxes and fill all passages used for wiring to seal the home
- Dispose of all old wiring, knobs, tubes, and other debris properly
With perseverance and attention to safety, you can successfully upgrade from outdated knob and tube wiring to modern electrical circuits. While tedious, removing this hazard from your home is extremely rewarding for safety and resale value.