If you are buying an older home you should know that the insurance industry is becoming more and more restrictive on insuring a home with knob and tube wiring.
What is knob and tube wiring?
Knob and tube electrical wiring, also called open wiring because the air is its biggest insulator, was commonly used in homes built from the late 1800s into the 1940s. Knob and tube is a 60 amp, single conductor, ungrounded system. It gets its name from the porcelain knobs used to secure wires in place and keep them from contacting combustible surfaces, and porcelain tubes used to thread wires safely through studs and joists.
Is knob and tube wiring safe?
Electricians may tell you that if the knob and tube wiring system (K&T) remains unaltered, has been carefully maintained and all repairs have been made by a knowledgeable electrician, K&T wiring should still be safe to use today.
Unfortunately, that is rarely the case. While K&T wiring was adequate for electrical needs at the time they were installed, current households have electrical power use never dreamed of at that time.
Most of these historic homes today have a combination of new and old wiring. The majority of problems with knob and tube wiring are caused by tampering and when alterations are made to the original system by amateur handymen.
The main concerns regarding K&T wiring today are:
- The wiring is old. The insulation is prone to drying and cracking with age, and may have cracked leaving exposed bare wires which creates a fire hazard.
- There is no ground wire. This makes it more hazardous, especially in areas where it can come in contact with water, such as kitchens and bathrooms.
- Overfusing circuits to higher levels of current. Changes such as adding electrical outlets and double tapping circuits increase the risk of heat damage or fire.
- Loose fill insulation can create a potential fire hazard. It was very common to insulate homes with loose fill insulation blown into attics and walls when K&T wiring was in high use. The amount of old insulation remaining today is usually well below current standards, and homeowners may want to blow in more insulation. This is great for heat efficiency in your home, but doesn’t allow heat from the K&T wire to dissipate, creating a potential fire hazard. The US National Electrical Code forbids the use of loose, blow-in, or expanding foam insulation over K&T wiring. This means that if you want to add insulation you must first remove active knob and tube wiring.
Insurance companies are denying coverage because of knob and tube wiring
As existing knob and tube wiring continues to age and electrical use continues to increase, insurance companies are becoming more and more strict on their coverage requirements for knob and tube wiring due to a perception of increased risk.
In fact, most standard insurance companies are denying coverage unless K&T is removed. I remember when they would give the new homeowner a period of time to make the change after buying the property but now they are simply denying coverage.
I work with an insurance broker who represents over 30 insurance companies. Only a handful will consider insuring a property with knob and tube wiring, and these non-standard policies are very expensive if you are lucky enough to get coverage at all.