How the Long-Forgotten Knob and Tube Wiring Method Could Save Your Home

What is Knob and Tube Wiring?

Knob and tube wiring was an early standardized method of electrical wiring used in North America from about 1880 to the 1940s. It consisted of single insulated copper conductors run within wall cavities, passing through joists and studs. Porcelain knobs suspended the wires between ceiling joists while porcelain tubes protected wires where they passed through joists and studs.

This old wiring method has largely been forgotten as homes have modernized over the decades. However, for historical homes that still contain original knob and tube wiring, this antiquated system may provide some surprising benefits compared to modern wiring methods.

Benefits of Keeping Knob and Tube Wiring

While knob and tube wiring is obsolete by today's standards, preserving it in historical homes offers some key advantages:

• It's compatible with old building materials - The wiring was designed to work within lath and plaster walls and ceilings. Attempting to replace it can damage fragile original plasterwork.

• It allows walls to breathe - Knob and tube wiring is open-air, unlike modern wires encased in plastic conduits. This allows moisture to evaporate rather than getting trapped in walls.

• It's unlikely to start fires - The heavy rubber and cloth insulation minimizes risk of short circuits and overheating. Fires are more likely to start from modern wiring than well-maintained old knob and tube.

• It's expensive to replace - Rewiring a whole house with modern wiring can cost tens of thousands of dollars. Keeping the original wiring saves major costs.

• It maintains a historic appearance - The knobs and tubes are unobtrusive, keeping a historic look. New conduits and boxes stand out and alter antique appearances.

Maintaining and Repairing Old Knob and Tube Wiring

While knob and tube can be beneficial, it does require proper maintenance and repairs:

• Inspect annually for damage - Look for cracked or damaged insulation, loose connections, or sagging wires. Address any issues immediately.

• Splice in new wiring with care - When making connections between old and new wiring, use junction boxes and avoid twisting different wire types together.

• Insulate knob and tube wires - Adding loose-fill insulation in attics and walls helps modernize the system. But keep insulation at least 3 inches from wires.

• Hire an expert electrician - Have a licensed pro experienced in knob and tube perform any repairs or modifications. Do not attempt DIY electrical work on old systems.

• Replace individual sections if needed - If certain wiring sections are dangerous or degraded, target just those areas for replacement rather than the entire system.

Is Knob and Tube Wiring Safe?

Knob and tube wiring meets modern safety standards if properly maintained and updated. However, there are caveats:

• The wiring lacks a grounding conductor, requiring GFCIs for safety.

• Old fabric insulation can degrade over time and turn brittle.

• Capacity is limited compared to modern wiring - lights may dim when multiple appliances run.

• Aluminum wiring added in the 30s and 40s is a fire hazard.

So while knob and tube can be safe, each system needs evaluation by an electrician. Proper repairs and updates are crucial. With good maintenance, preserving knob and tube protects home heritage while providing safe, reliable power. But negligence can turn old wiring into a serious fire risk.