I’ve got old knob and tube running through the house feeding about half my circuits. I’m wondering how dangerous it really is to continue to use it. It’s going to cost me around 5-7.5k+ to replace it and I want to make sure this is a wise move. Of course the electricians I’ve had over to provide estimates assure me this is 100% necessary. I remain unconvinced:
- it’s up to code
- From the FHB article “Is Your Old Wiring Safe?”: “Myth #1 Knob-and-tube wiring must be replaced. When the opportunity presents itself—during a remodeling project, for instance—I usuallyrecommend replacing old wiring. Some insurance companies won’t issue new policies or will charge higher premiums for houses with knob-and-tubewiring. However, if it is inspected, proves to be ingood condition, and meets your needs, there is no reason to rewire your house.”
I’m wondering what all of you think….
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Thanks, Mischa
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Replies
Mischa:
I own and have worked on homes with Knob and Tube. It is perfectly safe, but there is a "but"
Its safe because: (1) The wires are separated and there is little liklihood of a short circuit; (2) The guage is about 12 ga or better, so there is little chance of overloading.
Its unsafe because: (1) There is no ground; (2) the Insulation is quite brittle and can easily break if you bend it or mess with it; (3) It is difficult to manuver into new boxes and the like; and (4) Splices, like any long interrupted run, are problematic.
You can fix the ground problem and my advise is that unless you want to fool with it and put in new boxes, etc, you can leave it alone. I would make new runs for the kitchen (heavy electrical use) and the basement (furnace, ac, etc) and probably the attic (for home office or computer use).
Generally speaking, from what I have found out about this issue from research, it is safe if left undisturbed. That being said, if I were to tear into a wall for some reason or another, I would make the extra effort to swap it out anywhere I had access.
My house was built in 1929, and still has some old knob and tube in the walls and basement. It's a bit of a mix right now. The panels were switched out several years ago. I try to leave it alone, but if I have the opportunity to replace, I do.
What are your answers to these questions?
1. Have any "additional" connections been made to the original circuits?
2. Has any insulation been added where the wiring runs?
3. What does your home insurance company say? What will they say in the future?
Original, unaltered K&T is safe, provided there is nothing in contact with the wire, it is fused properly, and the fixtures are proper. Even altered, if done so properly, is ok.
But what your insurance company says is another story. And even if they insure the house now, this is one of those things that they may use in the future to drop you.
I don’t really know the answer to these questions as most of the cable is in the wall. I do now that someone spliced to romex up in the attic where it is exposed. Is there a service one can use to do a safety audit of some sort of ones electric to answer some of these questions? I’d rather not use an electrician for this as they all seem to think that “yes, 100%, this all needs to be replaced!â€If it all comes down to the insurance then I’d rather wait as I could always just do the work when /if they eventually refuse to insure.
Mischa:
A good electrician can do a safety audit of your wiring.
- Make clear up front that you want a report only, with all problems noted in detail (and ranked in severity) and recommendations and options for fixing problems found
- Find an old guy who knows what he's looking at, a firm that does residential repair work in areas that have a lot of K&T
- Expect to pay for the service
If you get a good report, then sleep well. If not, and you think the electrician was good, have him come back to fix one (or some or all) of your problems. Or get another electrician to fix, working from your audit report.
Jim
Edited 3/3/2009 1:30 pm ET by jimjimjim
Edited 3/3/2009 1:33 pm ET by jimjimjim
Mischa:
The advice you're geting is generally good. I'll add my 2 cents.
I own and have worked on homes with Knob and Tube. It is perfectly safe, but there is a "but"
Its safe because: (1) The wires are separated and there is little liklihood of a short circuit; (2) The guage is about 12 ga or better, so there is little chance of overloading.
(1) Dry air is a good insulator. (2) Yes but ... (see below)
Its unsafe because: (1) There is no ground; (2) the Insulation is quite brittle and can easily break if you bend it or mess with it; (3) It is difficult to manuver into new boxes and the like; and (4) Splices, like any long interrupted run, are problematic.
(1) In most cases, no ground isn't a problem, again see below. (2) K&T was frequently covered later in attics w/blown-in insulation. So crawling around in the attic could have disturbed it inadvertently. (4) Original splices were generally very well made and not a problem, unless messed with. (5) Shared neutrals are common, so there is potential for overloading when the main panel has been replaced and the K&T is spliced to newer wiring in junction box(es). The overload may actually be in the new wire. (6) The (aged) colors of wire insulation don't readily identify Hot from Neutral and paired Hot and Neutral don't always run together. Troubleshooting and repair can be difficult (and dangerous if improper fixes were done so that circuits are multiply fed).
You can fix the ground problem and my advise is that unless you want to fool with it and put in new boxes, etc, you can leave it alone. I would make new runs for the kitchen (heavy electrical use) and the basement (furnace, ac, etc) and probably the attic (for home office or computer use).
My experience is that you can't really fix the no ground situation without a wholesale rewiring of the circuit. Without grounds, use GFCIs liberally in locations around water, mind plug polarization and keep your appliances in good shape. And the advice of replacing kitchen (and bath) circuits with new grounded cable is good.
Scooter, I take it your computer is in the attic!!!
Jim
Attic?
Runs down stud bays are super easy. Thats the reason for 1-2 attic 20a circuits. Regards, Scooter "I may be drunk, but you're crazy, and I'll be sober tomorrow." WC Fields, "Its a Gift" 1934
Old K&T will need to be replaced eventually, but generally there's no "emergency" involved.
The problems with it have been fairly well expounded upon:
1) It's exposed and subject to damage in attics and cellars. Also, the stubs that run into outlet boxes and the like are often old cloth-covered romex-like cable with very brittle insulation.
2) It has no ground and often has hot/neutral mixup problems.
3) You can't (legally) blow insulation into stud bays and attics containing (in-use) K&T.
4) People will be reluctant to buy a house containing K&T.
5) Insurance companies may refuse to cover houses containing K&T.
The net is that LEFT UNDISTURBED it's almost always OK, but disturbing it in any way creates a risk.
Great. Thanks to all. I have a much better hold on the issue and will schedule a safety audit ASAP.
find an electrician who's not afraid of it and actually understands it.
it's safe if in good condition and not buried in insulation.
also should be only on a 15 amp breaker.
I work in alot of older homes, most have K and T. If a full gut isn't happening ... the usual plan of attack is, if it's in good shape, leave the lighting circuits as is. Run new receptical circuits with 20a breakers.
Jeff
Buck Construction
Artistry In Carpentry
Pittsburgh Pa
Knob and tube wiring is not, of itself, a dangerous wiring method. The problems that arise are more the result of how our lives have changed, and unqualified attempts to 'improve' it over the years.
Let's look at things in more detail.
First, the insulation of the old wire may be worthless, after years of putting 100 watt bulbs in fixtures rated for only 60 amps, or 30 amp fuses on wires that can only handle 15 amps.
Second, houses were built without the receptacles we now want, and our appliances simply didn't exist back then. So, over time, there are usually improper splices, multiple wires under one fuse, etc ... all potential sources of trouble. Even adding insulation to the attic creats a hazard, where the old wires are buried.
Finally, sometimes you NEED a ground. Even when you can get some protection by using a GFCI, the old panel won't take the breaker, and a GFCI receptacle won't fit in the old boxes; nor was any wire left for you to work with.
All considered, I would strongly encourage you to replace the K&T as opportunities present themselves. DO NOT tie into the old circuits; run new ones all the way to the panel, and use new boxes and devices.
I had the K+T inspected in one building by the electrical inspector. He asked us to protect it by installing blank faced GFIs on each relevant circuit. Cheap, fast and easy. Whew!