Knob and Tube Remediation
Knob and Tube wiring (K&T) was an early method of wiring in buildings in common use in North America from about 1880 to the 1940s. The system is considered both obsolete and a safety hazard.
Electricity is a powerful and potentially destructive force. We bring it into our buildings to do work. We do our best to tame and control it, but are never 100% successful. Even a properly installed modern wiring system built today has some level of risk associated with it. That level of risk increases greatly if the system contains even a small amount of K&T wiring. We can reduce, but not eliminate risk associated with a K&T system if it is minimized and modified by a licensed professional electrician that is familiar with this very old wiring method.
Facts About Knob and Tube Wiring:
- It is inherently more hazardous than modern wiring. The dangers from this system arise from its age, improper modifications, susceptibility to physical damage, and situations where building insulation envelops the wires.
- It has no bond wire (aka ground) and thus cannot service any three-pronged outlets or appliances.
While it is considered obsolete, there is typically no code that requires its complete removal.
- It is treated differently in different jurisdictions. In some areas, it must be removed at all accessible locations, while others merely require that it not be added to or installed in new construction.
Knob and Tube Wiring and Homeowners Insurance:
Some insurance companies refuse to insure homes that have Knob and Tube wiring due to the risk of fire. Exceptions are sometimes made for houses where an electrical contractor has deemed the system to be safe. Other insurance companies do not concern themselves with the type of electrical system in a home.
Advice for Those With Knob and Tube Wiring:
- Have the system evaluated by a qualified electrician. Only an expert can confirm that the system was installed and modified correctly. They can determine if it may be subject to use beyond its safe capacity.
- Completely rewiring a house can take many days, involves opening at least some walls and ceilings, and cost thousands of dollars. It is the absolute best way to deal with K&T wiring but it’s not the only option.
- The next best option is to remove as much of the knob and tube as possible, replacing it with modern wiring. Then an attempt should be made to remove as much known electrical load from the K&T system (appliances, large lighting loads, and outlets that may be used heavily). We then feed all receptacle outlets in the home with modern wiring. It is impossible to predict what device may be plugged into a particular receptacle outlet.
- An electrician should remove and replace any Knob and Tube wiring before it is covered with building insulation.
- Prospective home buyers should get an estimate of the cost of replacing K&T wiring in a home they are considering. They can use this amount to negotiate a reduced price for the house. They will be tempted to use the price reduction for other purposes but would be well served to get the K&T wiring problem repaired.