knob and tube wiring in house we may buy?

Hello, my girlfiend and I recently made an offer on a 2 bedroom 1 bathroom house and they excepted, this house is really old and we found out with home inspection it has the old type knob and tube wiring and is not grounded. we would want to put in the new style electrical wiring and update it. . does anyone know what this costs to do this?

I re-wired my old knob&tube 60 amp service house about 14 years ago. Aside from a load center, the materials are not that expensive. Under $2000 then as I recall. The main cost is the labor. Inspections alone will run hundreds of dollars in most locales. You will usually find in the old houses that pulling cable is not straight forward, they used to run 2x4s parallel to the floor about half way up the wall. You pretty much have to start from scratch but with the disadvantage of having all the walls, insulation etc in place. The original installation is done to the accessible frame--so much more labor intensive than a new house wiring. Also it is extremely unlikely that you have enough outlets, GFCI's etc. to satisfy code (it will not pass inspection unless it meets modern standards), so it is not just duplicating the old wiring setup in romex, but putting in a lot of new stuff. If you are not handy with tools or confident about your ability to handle electrical work safely, you have a MAJOR expense and if you are, you have a major project. Get a couple of electricians to give you a bid. Even in a recession with a lot of guys hungry for work, I think you will be unpleasantly surprised.

I am an electrician..... though now days I do mostly security related work....alarms, cameras, etc....

I did quite a bit of service changing and rewiring. Depending on the size of the house, the project will easily cost $4k to whatever. A service change alone can be $2k easily.

I hope the walls will be torn out (opened up) so the new wiring can go in almost like a new job. That would involve insulation, sheetrock, paint, and trim...... adding to the cost. 

It is possible to totally rewire a house with walls intact.... but that will generally add 15% to 25% to the cost due to increased labor costs.  I was one of the few electricians in this county that would actually do old work rehabs..... it's dirty, but at times fun. I found all sorts of antique bottles and stuff in the attics and under the houses.....

If your offer was low and the house has potential...... you can pull this off and have a nice house when it's all done. I would recommend learning how to do a few things yourself like tile and paint, and maybe basic door trim and stuff like that. Let the pro's handle the plumbing and electrical, heat & air, and the critical stuff that needs a professional to install it. I did all the electrical, most of the plumbing, and 90% of all the other work (tile, paint, trim, cabinets, mirrors, ) on my addition a few years back. I had the masonary, framing, insulation, HVAC and sheetrock done for me.  I estimated that I saved ...easily $30k on labor and material markup.  It also allowed me to upgrade my fixtures with the money saved. The home improvement stores in your area hold "classes" every Saturday morning for do-it-yourselfers to get the basics..... be there and learn.... it will save you money ...IF.... you do the job right.

Yep to all of the above. Lathe and Plaster walls? <--( More expense to remove and replace ) If it's an old house it probavly needs to be re-insulated anyway. If it has an attic that is accessible with no floor, you could probably get by with stripping the walls (cutting strips out where you need electrical put in is just a major PITA), redoing the electrical and other things I'm sure you'll find, re-insulating and re-covering the walls. But make no mistake, the house will be a war zone for some time.
I don't know the electrical codes in your area, but you might check on adding a new service, feeding the old one and the knob and tube with it, and adding grounded plugs and GFCI's from the new service. ( Much lessdestruction ) That's a long shot, it's usually not allowed. A lot of old timers say knob and tube is a good system. You should also check to see if you are required to upgrade the electrical upon buying the house because the grandfather clause may have expired in your area. A lot of headaches to check on.

Interesting thing I found out back in 2007 when I had an electrician in to take care of a couple of problems (they had to re-do the grounding of the incoming service amongst other things) was that even to just replace an existing duplex outlet I needed a licensed electrician to come in and make the change. This is in NJ. Don't know if it's part of the NEC or just Joisey beign weird.


No.... that is part of the NEC and a professional electrician will do the job right. You can't simply pop in a new duplex outlet on an ungrounded circuit. The code allows a GFCI but...... a good solid  ground is the best and safest way to go.  Jersey is weird.... but in this case, they are complying with the NEC. A solid ground "anchors" the 2 "legs" to a common reference voltage.... near zero at ground. This keeps the legs at 120v from ground and 240v between them. Loose the ground and the voltage between the legs stays at 240v...however the legs reference to ground depends on the load being used..... which means one leg could be at 80v to ground and the other leg will be at 160v to ground...... just imagine your DAW being on either of those legs with that voltage being that far off...... stuff will burn up. More than once I have been called to a house with these voltages and complaints that their appliances and light bulbs are burning out, and re-working the ground connection solves the problems. A loose neutral will also allow this to happen.

Knob & tube is theoretically a very safe wiring method...due to the seperation of the conductors.  However, the insulation tends to dry out and crumble off, creating a shock hazard, and of course, it's an ungrounded wiring method.  I would replace all K&T, as well as BX, and non-grounded Romex.

In addition, during certain times in the past, some electricians thought it was a good idea to wire houses with aluminum romex. It was cheaper than copper, and copper was in short suppply at the time and very expensive.....It was permitted by code at the time, and some of this wiring still exists in homes today. I would not sleep in a house wired with this stuff. It would have to come out and copper installed.

Yeah... good points on the grandfathering issue too. Sometimes, depending on the jurisdiction... inspectors will require upgrades. And you must complete it before they will let you move in and turn the juice on.

Guitarhacker
In addition, during certain times in the past, some electricians thought it was a good idea to wire houses with aluminum romex. It was cheaper than copper, and copper was in short suppply at the time and very expensive.....It was permitted by code at the time, and some of this wiring still exists in homes today. I would not sleep in a house wired with this stuff. It would have to come out and copper installed.

I lived in such a house, and I had no idea how dangerous the aluminum was until I read about it after discovering the "peculiar silver wiring" when changing out an outlet.  Can you believe we paid for a home inspection and it was never reported to us?  Like 500 bucks for nothing.  And we had no recourse.  I don't remember the details now but it was decided we were screwed.
 
I did pull all new copper in the whole freakin' house.  It was miserable.  I learned alot..but I did not enjoy it. 
 
Oh, and what's the deal with aluminum 220?  We're renting a house now with all copper wiring, but the 220 run to our electric stove is aluminum.  Why on earth would that be ok?  Seems like that would counter code or something. 

you guys are very helpful, I live in Lodi, California. The houses are going pretty quickly here. bidding wars.  the house looks like its from the 1920's or older but the date says unknown on the records. The home inspector said the foundation seems to be standing nicely, the faucets and toilet work. The gas was off  and the thermostat was missing so we are asking the seller to turn on the gas and check the heater, make repairs if neccesary. This loan is fha  so we are asking the seller to make all health and safety repairs.

What's "knob and tube" ?

The big problem with the AL wire to outlets is that there is two dis-similar metals in contact with each other.... that causes problems. And also the 12 guage aluminum will break easily after a few twists....and aluminum is a much softer metal so it "oozes" under pressure and the result is the connection becomes loose over time. A loose connection causes heating.... and heating causes...fire.

   A connection becoming loose isn't just common to aluminum.
What you say is true but may I add that workmanship is a
factor? I've seen connections "fail" everywhere from plugs on
up to even the power companies connections outside the
house. (be it aluminum or copper).

   There are so many other things as well that can cause
a connection to "fail" even if the workmanship is good in
the (say a wall plug). The wire in some of those "molded"
male plugs on such things as space heaters and window
a'c units and other things like a vacuum cleaner over time
start "burning into". As they do they heat up and make
the (wall plug) become warm and then onto hot.

  Many connection "failures" could have been caught
before the damage is done by simply knowing the
connection is "running hot". Many people that I have
spoke with (home owners) don't even consider a
connection running hot as a concern. I've had many
customers say to me for example something like:

  You know? when I turn on my light switch or remove
a plug from the wall it sure is hot! I say "Don't that
concern you?" most of the time the answer is something
like "it's no big deal!"

   I've even had people look at me like i was "shooting
them a line" when I say a hot wall plug is dangerous.
Oh my gosh don't get me started now! Here is another
one:

  I get a call. the customer says they're kitchen light
doesn't work. I take the glob off and there are these
100 watt (or more) light bulbs. Sometimes 3. I say
that much heat is dangerous and these fixtures
are not "rated for that much wattage". They say
Oh! "but I need the light" "its too dark in here!

   What happened? It not only burnt up the fixture
but also the wiring inside the box in the ceiling.
There are those people who do show a great
deal of "concern" over what heat does once they
know about the subject. I just think that it's sad
that those who think (or give me the impression)
that it's "no big deal" think that way.



  

Knob & Tube

 
I was wondering the same thing when I started reading this thread the other day.
Lo and behold, on This Old House today they're building an addition to a house which has K&T, and the electrician says it all has to go. Another 5-6 grand out of the budget.

We just abandon the old K&T and run all new wire (Romex) throughout the house. 
Usually everything from the service head out side, meter pan, panel, breakers, switches and outlets.

Cheap - NO
Safe - YES

Mike

Guitarhacker


What is Knob & Tube.......?  LOOK HERE

Thanks!

They popped a new code requirement in a few years back. It calls for the removal of all old and abandoned wiring that is accessable..... unless it is clearly marked for future use as a spare.

I run into this all the time, as I do upgrades on security systems. I have to remove the old wire. I think this is a good thing... time consuming at times..... but if you have ever worked on an old building that has had a number of systems.... computer networks, phone networks, security, and other, where the contractors left the old wire above the ceiling and in the attics...... OH MY.... what a confusing mess.

OT but I see that the quote function is still a mess.
Sheesh! it's either quote the whole damn message or quote part of the message but have no idea who the original quote was from.

Mike 

This post is very old. But the post is very impressive, nice guide, liked the suggestions here.