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#55868 - 09/07/05 02:32 PM Knob and Tube Advice?
Webmaster Offline


Registered: 10/07/00
Posts: 3142
Loc: NY, USA
from the ECN 'MailBag' ...
I recently put an older home under contract subject to a satisfactory engineer's building inspection. The inspection report notes significant knob and tube wiring and recommends an electrician's evaluation, pointing out that the presence of k & t can lead to problems with insurability. The k & t provides the service to 2nd floor bedroom ceiling fixtures and wall outlets, at least, and may provide more service elsewhere. An electrician looked at the house and told me he wouldn't touch the k & t because it would be such a complicated job, involving opening walls and ceilings. This puzzled me since I believed most of it was in the attic, but now I am thinking it's probably elsewhere as well. I have two concerns: 1) safety and 2) insurability, and then there is the factor of what I can reasonably afford to do. The house has a balloon frame structure which increases my fire hazard concern slightly but had made me think rewiring would be easier than with other types of framing.
Any general Advice??

[This message has been edited by Webmaster (edited 09-07-2005).]

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#55869 - 09/07/05 03:10 PM Re: Knob and Tube Advice?
Dnkldorf Offline

Registered: 12/12/04
Posts: 1091
Loc: nowhere usa
First, I'd tell him to get a 2nd and 3rd opinion.

I don't understand the "opening walls" statement. Leave the stuff in the walls and fish down new circuits.

Go as you can afford, have someone do a little at a time.


#55870 - 09/07/05 03:19 PM Re: Knob and Tube Advice?
HotLine1 Offline


Registered: 04/03/02
Posts: 6792
Loc: Brick, NJ USA
AS an AHJ, and an EC, K&T that has NOT been 'modified' usually does not present a problem

The OCP that protects the K&T circuits should be checked as to proper amperage firstoff.

Yes, K&T is 'in' walls, but there is no need to open the walls, unless you are determined to remove the K&T.

"Fishing-in" as Dnk said is the way to go!

As to the lighting outlets (ceiling), what I have seen in 25 years+ is insulation deterioration from heat from the bulbs. Old fixtures lacked any insulation in the canopy, and people installed all kinds of bulbs over the years.

Peace of mind will require installing new wiring; it is the way to go if you are thinking about any renovation projects. A good lic. EC will 'fish' new lines, with little or no plaster damage. Remember, you get what you pay for!!

There is nothing within the scope of the NEC that mandates removal of K&T wiring.

AS to the insurance thing, that answer is best left to a qualified licensed insurance professional.


#55871 - 09/07/05 03:43 PM Re: Knob and Tube Advice?
Joey D Offline

Registered: 10/10/03
Posts: 263
Loc: Arlington MA U.S.
1st thing you need to do is shut of any power that is on the system and see how much is acually working. I have had plenty of projects like that. New home owners move in only to find out that their insurance is going to be cancelled. I don't agree with that but it happens. Get a few prices on the job and see if can be used to get a better price on the house to offset the cost.

#55872 - 09/07/05 04:05 PM Re: Knob and Tube Advice?
earlydean Offline

Registered: 12/22/03
Posts: 749
Loc: Griswold, CT, USA
Gut the house. Remove all old wiring and piping. Repair the dry rot, remove the insects and rodents, plug all the openings they got in from.
Install all new wiring and plumbing. Insulate the walls, install new sheetrock. Paint and trim. Install a new roof and cover the old siding with vinyl.
It might be cheaper to simply buy a new house?

#55873 - 09/07/05 05:58 PM Re: Knob and Tube Advice?
e57 Offline

Registered: 05/27/03
Posts: 2837
Loc: S.F.,CA USA
It may be only a regional thing, but insurance companies here don't seem to mind K&T, as it represents >60% of housing stock as original wiring method. Most of my home still is... Screw in fuses on the other hand - NO DICE!

As for keeping it. That depends on the "grade" of wiring that was put in as original. As we do even now, there are different grades of wiring that we do. (i.e. bare min, or full kitty.) Some of the bare min homes had at most, a single 20A circuit for the kit, and lighting only, one each room. Full kitty had many outlets (Comparable to one circuit every 2 rooms.) and depending on when it was put in a few in the kitchen. As well as robust lighting layout and switching. (Maybe even gas and electric lighting depending on when installed.) Of course much of this housing stock was the McMansion of the day. Later on might even see K&T with seperate bare grounding to the nearest water.

Like mentioned before, unless some jerk in the 70-80's messed with it, (For some reason that seems like a very bad vintage for the electrical trade.) it was originally installed with, for the most part, the highest quality workmanship. Of course it is limited (like any instalation) to circuit load capacity. And, could last many more years, if not abused... Shorts, over-loading, etc.

As for code, 394 has some guidelines for what can, and can not be done with it.

In some closed remodels I keep the lighting, and ditch the outlets. (If in good shape, insulation still suppel, etc.) Some cielings here have archetechual elements that are too expensive to re-do, or replace. Splice and solder (In the same method it was done in) some length to make it to a box suitable for feeding it from, and re-feed it from a new circuit if need be. (Lately, AFCI circuits.) Re-use the Knobs & Tubes, or get new ones from one particular supply house that carries them. Although allowed, I never extend from it.

MPO... It is much less a hazard than the average 3-wire circuit, unless it was abused by over-loading, or exposure. All but some of the very late ones were 2-wire circuits completely isolated from framing, with no insulation in the walls, practicaly free air cooled circuits. Splices were cleaned isolated from movement, mechanicaly made, (Western Union etc.) then soldered and cleaned again, and preserved in tape. Considering, the age of some, (over 100 years) they rarely failed.

Any general Advice??
Keep the lighting, unless the load changes.

Ditch the outlets, the load HAS changed, add new. Any Electrician worth his salt would be happy to, and know how to do that. That is after all what we do!

Forget about insulating the walls and cielings, if you have already, bust open that joint and start over.
Mark Heller
"Well - I oughta....." -Jackie Gleason

#55874 - 09/07/05 06:39 PM Re: Knob and Tube Advice?
dmattox Offline

Registered: 10/20/04
Posts: 267
Loc: Anaheim, CA
Due to the physical separation of the conductors K&T is safe when left alone. What’s left of the insulation on most K&T will crumble at the slightest touch so crawling through the attic can be a dangerous adventure.

Homes with K&T usually have fewer devices per square foot than today and the K&T I have seen always has been installed in a very professional manner. So you are not likely to have a rats nest of it in the attic.

My house has K&T and I don't loose sleep over it. While if I found out I had aluminum I would be ripping out the walls tonight.

My main area of concern with K&T is where it enters J-Boxes, since this is where it looses the protection of physical separation. However there is no easy way to check the junction boxes without possibly making the situation worse. And if there is an issue, that’s what the j-box is there for, to provide protection.

#55875 - 09/07/05 07:56 PM Re: Knob and Tube Advice?
distributor x Offline

Registered: 07/28/05
Posts: 57
Loc: Canada
"My house has K&T and I don't loose sleep over it. While if I found out I had aluminum I would be ripping out the walls tonight."

If proper devices (colar) or proper connections (pigtails) are used, what is the big deal with aluminum wire?

#55876 - 09/07/05 09:09 PM Re: Knob and Tube Advice?
SvenNYC Offline

Registered: 08/19/02
Posts: 1685
Loc: New York City
Exactly the point.

IF the proper methods are used.

Not everyone knows that, unfortunately. Some people think that you can use any old 50-cent device with aluminium wire and not have problems.

#55877 - 09/08/05 12:34 AM Re: Knob and Tube Advice?
Trumpy Offline


Registered: 07/05/02
Posts: 8532
Loc: SI,New Zealand
As far as K&T goes,
It sounds like it's time for an upgrade.
Just my opinion.
Let's face it, these days if you're not young, you're old - Red Green grin

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