Just received this informative email from an inspection company in the area and thought I would pass it along. As a Realtor in the Hyde Park.Oakley area, I see knob and tube wiring all the time and I get A LOT of questions about it. So here is a primer for those of you that want to know a little more. Courtesy of Pillar to Post Home Inspections.
If your home was built prior to 1950, you may have a knob and tube wiring system. Though the technology is older it is still capable of carrying electricity throughout your home. There are additional factors, however, that homeowners should know about when buying or selling a home with knob and tube wiring.
What is Knob and Tube Wiring?
The system uses porcelain insulators (knobs) for running wires through unobstructed spaces. Porcelain tubes protect wires that run through studs and joists. The two electrical wires are wrapped in a rubberized cloth, and are run suspended through the walls. In contrast, modern systems have a third additional “ground wire” and three-prong outlets that add an extra measure of safety.
When is it Unsafe?
Installations have to be evaluated on a case by-case basis. Safety usually depends on the history of modifications and upgrades. While an electrician can do a proper splice, Pillar To Post home inspectors often find inappropriate splices which create a serious safety hazard. Because knob and tube wiring was designed to let heat dissipate to the surrounding air, most energy efficiency upgrades involve insulating previously uninsulated walls. They also usually require replacement of the wiring in affected homes.
As existing knob and tube wiring gets older, insurance companies may deny coverage due to increased risk. In fact, many home insurance companies will not write new policies on homes with knob and tube wiring. If you are buying a home, you may have to upgrade part of or all of the system. Some insurance companies will insure you through the transaction but will require you to upgrade within a defined period of time.
Updating the Wiring
It’s often not too expensive if you only have a few knob and tube circuits to replace. But, if the home has knob and tube wiring throughout, an upgrade may involve more than just replacing existing circuits. It may require upgrading the breaker panel which can be expensive. In an upgrade, the wiring will be updated to meet today’s standards. In the end, it is generally well worth the expense to upgrade to the safer modern electrical system.