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from Historic Home Buyers/Owners

This months question:
Knob & Tube Wiring
I am in the process of purchasing a Victorian home built around 1880. There is a 100 amp fuse box and old cloth covered wiring that passes through porcelain tubes. An older couple currently lives in the home which has had very little updating. Will this wiring and the old fuse box need to be completely replaced? Will we need to tear open the plaster walls? Any help would be appreciated.
Thanks, JG

Amongst experienced inspectors and even electricians, there are varying opinions on how knob and tube wiring should be addressed. The two most immediate concerns are:
1) If it is encapsulated by insuation that was added to an attic, wall cavities, crawlspace, etc.
2) Improper alterations can seriously effect the original design.
The comments below are general and do not apply to all situations. This should not be considered advice and certainly can not replace the need for a complete pre-purchase inspection by a qualified professional inspector or licensed electrician.

From your description, it sounds like you have knob and tube wiring in your home. This wiring is ungrounded, and, by today's standards, is not safe. Problem is that, overtime, the insulation wears thin or falls apart, or is eaten by mice, and the conductor is exposed. This can, under certain conditions, cause arcing and lead to a fire, or cause someone to be shocked, should they come in contact with a bare wire. Sometimes folks have tapped into the existing wiring, to add other circuits, and these connections are also unsafe. To answer your questions - it is strongly suggested that all old knob and tube be removed and replaced with modern wiring. As for breaking through the plaster, an electrician experienced with older homes can oftentimes fish new wiring through the often uninsulated walls without too much destruction.
Good luck. Ken Salvo, HBIA Member Inspector

Personally I have renovated at least 10 homes with this set up. The 100 amp fuse box is minimal at best and I have always replaced it with a breaker system. I have kept the cloth wiring in the walls, except in kitchens and baths, where I have gone to new wiring with GFI's. I personally have not seen the necessity of replacing all the old wire behind the walls. Usually if it shorts a breaker will trip. Everybody is different, for me unless the wire is totally damaged, I am going to use it.
Bob Congdon, HBIA Member Inspector

Local codes generally set minimum standards for updating an electric system. When work requiring a permit is being planned, this minimum updating usually is incorporated into the project. While it may not be necessary to remove the fuse box for safety reasons, usually it cannot accomodate modern usage levels particularly when it comes to 220 volt circuits and expansion. Assume that the panel needs replacing. The exposed knob and tube wiring in a basement usually does not comply with modern standards because of open wire splices and other discontinued practices. Usually, it needs to be replaced. Both of these work items will make your system safer and easier to work with.
Replacement of knob and tube wiring in an attic or in walls is generally not required but sometimes because of the placement of the outlets, desire for grounded circuits, and configuration of the circuits, it is better to use new wire.
I advise that you obtain a bid from an electrician for updating the system to meet modern standards. Then, if possible, plan for and include a wish list of additional outlets, lights and switches and new 220 volt circuits and obtain a bid for this work as well. At the time of purchase, safety deficiencies to the system and, to some extent, improvements such as a 220 volt circuit for a clothes dryer can be topics for negotiation.
Most of the time when electric work is done in an older house some small access holes will need to be cut in the plaster walls and ceilings. Discuss this with the electrician and plan for it.
In our area, some property insurance carriers want to know if a house has a fuse box. This probably means that they may be charging more for the policy or not underwriting houses with the older systems.
Good luck. Jon White, HBIA Member Inspector

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