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[OP]
Member
Oct 27, 2013
280 posts
75 upvotes
MISSISSAUGA

Knob and tube

Hi all. Knob and tube is pretty easy to identify if the ceilings or walls are exposed. But if not, how would in be able to tell? Is there something distinct at the panel that would indicate this? Or some other hint? Thanks
13 replies
Deal Addict
User avatar
Mar 8, 2002
4232 posts
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Ottawa
Drywall hides a lot of sins. Some unscrupulous person could replace all the exposed wiring in the basement with new wiring, and leave knob and tube hidden elsewhere. It's always a case of buyer beware. Having a reputable home inspector that goes everywhere and does a thorough job is extremely important, although in the GTA housing market that is really no longer a concern. So in the latter case, having an experienced agent knowing the age of the home can advise.
[OP]
Member
Oct 27, 2013
280 posts
75 upvotes
MISSISSAUGA
MacGyver wrote: Drywall hides a lot of sins. Some unscrupulous person could replace all the exposed wiring in the basement with new wiring, and leave knob and tube hidden elsewhere. It's always a case of buyer beware. Having a reputable home inspector that goes everywhere and does a thorough job is extremely important, although in the GTA housing market that is really no longer a concern. So in the latter case, having an experienced agent knowing the age of the home can advise.
Thanks for the information. I do have a good understanding of construction and can identify exposed K&T. But how would a thorough home inspector be able to identify this behind drywall? Is there some other way to identify it besides observing it in exposed joists/studs?
Deal Fanatic
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Oct 19, 2008
6654 posts
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GTA
newby1983 wrote: Or some other hint?
Image

Or even better, gas lights in the house Smiling Face With Open Mouth
Seriously though it would be visible at the panel.
Deal Addict
User avatar
Mar 8, 2002
4232 posts
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Ottawa
Using an electrical tester to check for missing ground, or removing a receptacle and looking for clues as to the age or condition of wires inside can help, but there is no sure way to know if every piece of wire has been upgraded.
Deal Addict
Nov 17, 2012
3289 posts
2272 upvotes
Toronto
Check the points where wires connect to each other. Switches, light boxes, outlets. In any one of those you could have a marriage between knob/tube style wiring, aluminum and/or copper.

Otherwise, as people have said, some idiots connect wires with electrical tape in walls and hang drywall over it. Impossible to find.

Maybe there is some fancy gadget that puts load on a circuit and then using a heat sensing camera, spots heat signatures in the walls where connections are / different conductors, but I've never heard of that. Just making it up.

If there is a trace of live knob/tube wiring in the house, I'd assume you need to rewire the entire place. Always assume worst-case.
Deal Addict
Dec 24, 2007
1937 posts
463 upvotes
Toronto
I remember those switches in my house before renovation, classics!

I had several places where the KnT was just cut off and plastered over, really hard to even tell there was a switch there before. In the basement they had new wiring to a new breaker box(replaced during the big winter storm) but somehow the KnB was covered up and inspection passed.

During our renovations we noticed several burn spots on the wood, really glad we got rid of all the KnT.

Cheers!
Zamboni wrote: Image

Or even better, gas lights in the house Smiling Face With Open Mouth
Seriously though it would be visible at the panel.
Thread started in 2016 - 1927 fully gutted and renovated 2 storey detached home in the big T.O. - small projects still in progress.

RFD priceless!
Sr. Member
Sep 12, 2008
575 posts
198 upvotes
Hamilton, on
I would find a few ceiling lamps/outlets that look like they might be "harder" to get to than normal. Take out the fixture and inspect the incoming wire. If you see a typical white 14/3 wire, you SHOULD be good. If you see two separate (usually both black and "cloth covered") coming in theres a good chance its knob/tube.

You def. DONT want knob/tube outlets, they cant run modern things like a laptop. Ceiling lights are less of an issue. Undisturbed, knob/tube is no more of a fire hazard than modern electrical.

Just finished replacing the last of mine in a house I bought that was 80% converted. Guy skipped out on a few hard to get to lights. Was doing some wall/ceiling work so that was the time to pull new 14/3 through.
Deal Addict
Sep 11, 2006
1382 posts
356 upvotes
Toronto
GodSendHockey wrote:
Undisturbed, knob/tube is no more of a fire hazard than modern electrical.
Depending on what you mean by undisturbed, this statement couldn't be more wrong. Mice love knob and tube wiring and given the age of a home that has knob and tube, it is 100% going to be disturbed, whether by mice or renovations, large or small. Modern day electrical has a ground wire and very recent modern electrical is all arc fault protected.

Please don't make statements like this because will take them seriously and upgrade other frivolous things before making their home electrical safe.
Deal Guru
Jan 25, 2007
10083 posts
5337 upvotes
Paris
Zamboni wrote: Image

Or even better, gas lights in the house Smiling Face With Open Mouth
Seriously though it would be visible at the panel.
My Uncle had these everywhere in their farm house (my Mom lived there as a kid when they got the electricity). He bought a couple of new ones for switches here and there that are in this style and cost $100+ a crack.
Deal Guru
Dec 31, 2005
13306 posts
736 upvotes
newby1983 wrote: Hi all. Knob and tube is pretty easy to identify if the ceilings or walls are exposed. But if not, how would in be able to tell? Is there something distinct at the panel that would indicate this? Or some other hint? Thanks
First you will probably have fuses. Not that you cannot mount to a breaker, but it is a clue.

Really though, anyone looking at the wires entering the panel will be able to see if they are grounded or not...which is a dead giveaway. At an outlet, just test it for ground. They really shouldn't put a 3 pronged outlet in, but many will still do so...

Of course, just seeing k&t doesn't mean it is still live either.

Both of our houses in Toronto had or still have K&T. At our first house, we had the K&T for 5 or 6 years until we did a full basement get and rebuild. At that time we also did the electrical.

In our current house, the Kitchen, the family room addition and the upstairs bathroom are modern (as well as the hot tub and AC) and the remainder is on K&T from original build in 1940. Eventually we will replace. Right now, the K&T only really has a few outlets and the light switches on it. There are no TVs or Computers in any of the bedrooms or living room.
Deal Guru
Dec 31, 2005
13306 posts
736 upvotes
DIrty-D wrote: Depending on what you mean by undisturbed, this statement couldn't be more wrong. Mice love knob and tube wiring and given the age of a home that has knob and tube, it is 100% going to be disturbed, whether by mice or renovations, large or small. Modern day electrical has a ground wire and very recent modern electrical is all arc fault protected.

Please don't make statements like this because will take them seriously and upgrade other frivolous things before making their home electrical safe.
Many people live with K&T today...as we do. Many also have a both modern and K&T wiring. We have never had an issue, but we also don't do silly things. Our old K&T really only is for lights and the basic outlets. No computers, TVs or other major draws are used on the K&T circuits.

The Electrical Safety Authority as well as the Ontario Electrical Safety Code recognize and accept knob and tube wiring methods.
The Ontario Electrical Safety Code 2002 edition contains rules that govern the installation of open type wiring methods (knob & tube). Rules 12-200 to 12-224 set out the minimum safety standards for the installation of open wiring, which may still be installed to this day.
Deal Fanatic
Jul 3, 2011
5825 posts
2976 upvotes
Thornhill
As Macgyver said, use an electrical tester on outlets. Where there is knob and tube present in a house there will always be ungrounded outlets and usually fewer outlets as well.
badass wrote: I had several places where the KnT was just cut off and plastered over, really hard to even tell there was a switch there before. In the basement they had new wiring to a new breaker box(replaced during the big winter storm) but somehow the KnB was covered up and inspection passed.
This is far more common than most people think and also dangerous.

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