K&T End?

Approximately when (range of years?) did new home builders stop using knob and tube wiring?

**Electrical Tip of the Day: **Knob and tube electrical wiring was installed in homes from the 1920’s to the mid 1960’s – later in some rural locations.


I’m sure it varies by region.

Based upon my personal observations in Minnesota, Iowa, Washington, Oregon, Illinois…

Installed from approx. 1880 (depending when electricity was available in your area)…

Generally (openly) installed until the 1930’s…
Marginally (occasionally) installed until the 1940’s…
Sporadically (Rarely) installed until the 1950’s.

That kinda fits with what I was thinking (recently saw some still in service in a 1893 home), but I looked at a rural GA home today that was said to date back to approx. 1915. Saw no evidence of K&T, but plenty of early cloth covered 2 conductor cable (some pretty rotten). I suppose someone could have removed all traces of K&T during an early upgrade, but we will probably never know.

it was widely used until the early to mid 60’s in northern Ohio…

My first job back in 1966 was K&T.

It can be repaired till this day

Very interesting - I had no idea it was installed as late as that. Based on what I have seen, it was not widely used around here past the early 1900s. But based on the possible range of years it could have been installed, it is obviously not much use in approximating a home’s age


From time to time I get a call from someone about a post I made.

I hope this finds its way to the Georgia “Master Electrician” that took me to task for stating that knob and tube was still being installed in the '60s.

I guess some Masters just don’t know every thing. Enjoy


In my area you see it from 1800’s into the early 1940’s

Amazingly that stuff is still in the NEC. :roll:

1960 working with my old man, was all romex.
Never encounter K&T unless it was a building built in the 30’s.

Northern Maine.

I started the trade in Ontario in 1951 .
They did teach it in Trade school but we never saw any new installation in the field .
All two wire romex no ground.
The conduit was black painted and it frequently broke when being bent .
It also had a seam and this frequently would open up when we cut and threaded it .
Much by hand no power tools in many cases .
Try and thread 2 inch with a solid pipe threader non ratcheting a two person job .

Damn your old Roy, that’s the year I was born. :mrgreen::wink:

House I have here is 67 built, with romex wiring 12/2 with ground 18 gauge and mostly 14/2w/g.
But all the ground wires were cut off for the old two prong devices.

I started when I was 15 but they would not count that time .
You had to be 16 to do an apprenticeship so I lost 5 days .
I worked with my brothers from when I was twelve ,they both where electricians .
no knob and tube then either here in Ontario

I’m nowhere near as old as You guys , but it’s my understanding that the unions pushed to keep K+T here into the 60’s…

Yeah, right buddy. :):wink:

That’s the same union I belonged to for almost 60 years and I never saw this info before

well I was a union carpenter and not an electrician Roy but I do know this to be a fact in this area…the knob and tube was being installed here well into the 60’s and it was because of the IBEW…prolly just a local thing…

Union Carpenter as well in 1969 and never so it installed anywhere.
Local thing it must have been.

My Fathers house had romex wiring and was built by him in 1935-40:)

The key is when did the jurisdiction in which you live start having code enforcement. I started in the electrical trade in the summer of 1966 but the jurisdiction in which I started did not have an inspection department until the early 1980s and then it was just an electrical inspector. A few years later came the building inspector which was followed by plumbing and mechanical.

The only other eyes that saw our electrical installations was the person that connected the power to the house and he would do somewhat of an inspection. If memory serves me correctly it was also the utility person that drove the ¾ inch metal water pipe in the ground for the electrode and installed the riser from the meter up. In some areas around here the utility will still install the riser from the meter up.

Don’t be fooled by Knob and Tube as the installation of this wiring method is still allowed today by the 2011 NEC
**394.10 Uses Permitted. **
Concealed knob-and-tube wiring shall be permitted to be installed in the hollow spaces of walls and ceilings, or in unfinished attics and roof spaces as provided by 394.23](http://code.necplus.org/document.php?field=jd&value=necss:70-2011:id02011008623#70-2011:id02011008623), only as follows:
(1) For extensions of existing installations
(2) Elsewhere by special permission


The link above is to a public building that the K&T is maintained daily. Some of which is exposed.