# Tricks to Knob and Tube rewiring



## cwatbay

There are a lot of sparkys that have much more residential experience than me and maybe you have some ideas on rewiring homes that have knob and tube wiring. 

95% of our work is commercial so residential comes along every now and then. But here is the scenario: HO wants the old K&T removed because they heard it's old and possibly dangerous, or, they want to put in insulation -- which is not so great if you have K&T, or, they have just had too many electrical problems and they blame the K&T. 

Typically, these home are older, and, tend to be lathe and plaster, but not always. Also, the HO's don't want to channel the walls and ceiling (red flag), don't want to spend much money (red flag), don't want the expense of permits, new panel, etc (red flags). 

This gets really interesting in multi story homes, and, I find a lot of the old K&T goes down the inaccessible outside walls that have multiple fire breaks. 

Oh, and don't let me forget that almost always, an HO, Hack or Handyman has run Romex from the panel up into the attic to one or more Jboxes where they spliced in the K&T when things got tough. These are usually hidden in blown in insulation or some other places where they are not readily apparent. 

Any advice on how to handle these kinds of jobs from some more experienced sparkys would be appreciated. Even if the client is not a cheap, demanding jerk. Thanks.


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## Inner10

Yeah, rewire the house, bid it high, learn how to fish wires. Done deal.


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## 480sparky

If the customer is too cheap to correct a problem, I move on to greener pastures. Problem solved.


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## cwatbay

I don't think there is any way around the "grunt" work. But correct me if I am wrong. The hardest parts are the outside walls with fire breaks. You can't access through the attic due to the slope of the roof, so it looks like you have to go up via an existing outlet, or, make a new one. 

The easiest thing is to just channel the wall from floor to ceiling and pull out the old and put in new (sometimes you can use the old holes in the breaks). Is there another way ? 

We fish wires all the time for LV applications and sometimes for standard electrical. Glow rods, chains and our Fiber Optic Cam (which has paid for itself several times over). 

I guess my question is: how would you do it, other than just trying to be as creative as possible (which takes time and is chancy). I was hoping to have missed a major clue, or, that someone who has done a lot of this has some hints.


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## hdavis

Where you'll have problems fishing, trace the existing wires with a NCV tester so you know where they generally are. Trenching walls isn't necessary, you can usually use a hole saw to put a 3-4" hole below the ceiling and one above the baseboard. Fiberglass sticks are real real handy. You'll find plaster walls have the last few inches at the bottom filled with plaster that dropped off during the plaster job. You don't have this problem with plaster ceilings. Usually you'd fish across the ceiling and then down the wall instead of horizontally trenching the walls. Exterior walls usually didn't have fire blocking, but they do have cross bracing near corners. You can map out the framing with a stud finder.


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## Inner10

> I don't think there is any way around the "grunt" work. But correct me if I am wrong. The hardest parts are the outside walls with fire breaks. You can't access through the attic due to the slope of the roof, so it looks like you have to go up via an existing outlet, or, make a new one.


Sure you can just get a young guy to crawl, then drill on an angle and feed a wire fish down. Then use a hole saw where the fire break is, notch it with your MM and screw the plug back in and mud it. If you are only going up one floor and you need the wire up at sconce level above the fire break feed a 6' bit up there. 



> The easiest thing is to just channel the wall from floor to ceiling and pull out the old and put in new (sometimes you can use the old holes in the breaks). Is there another way ?


:blink:



> I guess my question is: how would you do it, other than just trying to be as creative as possible (which takes time and is chancy). I was hoping to have missed a major clue, or, that someone who has done a lot of this has some hints.


Its as much art as science.. wire fishing is probably one of my best skill sets and it was acquired from working many years as a wire jockey doing grunt work. The reason I say it is as much art as it is science is every house is different, no two fishing jobs are exactly the same. Half the time you will plan out a route, run into a snag and completely change your approach. 

I should probably write a book on wire fishing. :laughing:


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## cwatbay

hdavis said:


> Where you'll have problems fishing, trace the existing wires with a NCV tester so you know where they generally are. Trenching walls isn't necessary, you can usually use a hole saw to put a 3-4" hole below the ceiling and one above the baseboard. Fiberglass sticks are real real handy. You'll find plaster walls have the last few inches at the bottom filled with plaster that dropped off during the plaster job. You don't have this problem with plaster ceilings. Usually you'd fish across the ceiling and then down the wall instead of horizontally trenching the walls. Exterior walls usually didn't have fire blocking, but they do have cross bracing near corners. You can map out the framing with a stud finder.


Thanks for the tips. That makes sense. You are correct there is cross bracing in the outside walls ---- lots of folks call it fire blocks regardless of the wall location - I was just lazy.


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## hdavis

Few things slow the job more than using battery drills and dull bit / saws. You're going to be dulling a lot of them, so keep plenty on hand, and change them out when they start slowing. I only use heavy duty plugin tools - higher drilling speeds. I once watched a Journeyman spend 45 minutes drilling through a beam with an 18V drill and a dull bit - works fine if you're paid by the hour. Also, if this is balloon framed, you can find all kinds of stuff in the outside walls. A lot of times it's sawdust, but I've found bricks, broken bottles,... They'd drop this down from the attic. Go easy when you're breaking through the lath with a hole saw - it can break the lath up pretty bad. I mentioned that you can have a bunch of plaster inside the base of wall. It's fastest to drill up through this than down through it. My favorite way of cutting in for boxes in plaster is to use one of the multitools. Very precise cut, not much risk of busting up the lath, so it makes for a neat job. A sawzall works faster and plenty electricians use them, but they can make an awful mess.


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## hdavis

Inner10 said:


> Sure you can just get a young guy to crawl, then drill on an angle and feed a wire fish down. Then use a hole saw where the fire break is, notch it with your MM and screw the plug back in and mud it. If you are only going up one floor and you need the wire up at sconce level above the fire break feed a 6' bit up there.
> 
> 
> 
> :blink:
> 
> 
> 
> Its as much art as science.. wire fishing is probably one of my best skill sets and it was acquired from working many years as a wire jockey doing grunt work. The reason I say it is as much art as it is science is every house is different, no two fishing jobs are exactly the same. Half the time you will plan out a route, run into a snag and completely change your approach.
> 
> I should probably write a book on wire fishing. :laughing:


I agree with all this. One guy can give up on a tricky fish after 2 hours, and the next guy can get it in 30 minutes. And skinny guys are always handy.


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## woodchuck2

As said above experience fishing wires is a huge help. Around here the trouble i run into with knob/tube is most of these home were post and beam and were later then remodeled with fire stops. Nothing like trying to drill through an 8" beam sitting on stone to get access into a 4" wall, only to go 4' and stop again. Same for the ceilings, your still drilling a 7-8" beam everywhere you go. When it comes to these homes everything is time/materials and i usually push to gut the walls. Sometimes what it may cost for me to remove all the old wiring, fish in receptacles around a room, fish a new light circuit, they may find it to be cheaper to tear out, re-install drywall with fiberglass insulation.


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## cwatbay

woodchuck2 said:


> As said above experience fishing wires is a huge help. Around here the trouble i run into with knob/tube is most of these home were post and beam and were later then remodeled with fire stops. Nothing like trying to drill through an 8" beam sitting on stone to get access into a 4" wall, only to go 4' and stop again. Same for the ceilings, your still drilling a 7-8" beam everywhere you go. When it comes to these homes everything is time/materials and i usually push to gut the walls. Sometimes what it may cost for me to remove all the old wiring, fish in receptacles around a room, fish a new light circuit, they may find it to be cheaper to tear out, re-install drywall with fiberglass insulation.


I would agree. We have only done a couple of knob and tube re-wires for HO's. The trouble is, none of the HO's want to hire another contractor to come in to plaster and paint. But there are more than enough hacks and handymen around who will do these jobs for just enough money to buy booze and meth for the weekend. 

We do use my fiber optic cam, glow rods, stud finder and other tools for fishing wire in walls. We do a lot of network wiring, plus home auto and some new sub-panels. Buy like I said before, residential is maybe 5% of our business ---- not because it's a pain or I don't like HO's, it's just because there are fewer and fewer folks who are willing to spend the money to do it right or even pull permits.


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## hdavis

cwatbay said:


> I would agree. We have only done a couple of knob and tube re-wires for HO's. The trouble is, none of the HO's want to hire another contractor to come in to plaster and paint. But there are more than enough hacks and handymen around who will do these jobs for just enough money to buy booze and meth for the weekend.
> 
> We do use my fiber optic cam, glow rods, stud finder and other tools for fishing wire in walls. We do a lot of network wiring, plus home auto and some new sub-panels. Buy like I said before, residential is maybe 5% of our business ---- not because it's a pain or I don't like HO's, it's just because there are fewer and fewer folks who are willing to spend the money to do it right or even pull permits.


A few more notes...

Each one is different, but if it's still all plaster and lath or drywall over plaster and lath, it usually takes 2 hrs per device through device out for experienced crews. A lot of places you don't have to remove all the old knob and post, just as much as you can reasonably access, so that saves some time. If the people patching are really bad, the obvious key is to make it really really easy for them. If it's drywall over plaster and lath, use a 6" hole saw through the drywall, then 4" through the plaster and lath - it gives the patchers a very easy patch to do. It helps if you screw the drywall piece you took out to the wall near where it came out - the patchers can just bevel the edges and put it in. You can do something similar with the plaster and lath, just going through the plaster with a 6 inch, then through the lath with a 4", but that's really coddling these guys. Try to keep them at least 2 inches from any trim or corners so the patch can be blended. There isn't any secret to taking out existing boxes - a lot of damage can happen there with a sawzall, but there isn't much choice. A metal cutting blade is less likely to hook onto the lath and pull it off the framing.


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## jarvis design

I'll start this post by saying I'm not an electrician! That being said, I have been doing sales for an electrical contractor since September and we do a LOT of k&t! Can't help too much with the actual work, but, I can tell you having an up-front pricing system is, IMO, a huge benefit. HO's know what the cost is and we guarantee that price. Most other electricians here base their price on how busy they are! Being we specialize and advertise for this type of work, we do more k&t than anyone else in town.


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## 480sparky

jarvis design said:


> I'll start this post by saying I'm not an electrician! That being said, I have been doing sales for an electrical contractor since September and we do a LOT of k&t! Can't help too much with the actual work, but, I can tell you having an up-front pricing system is, IMO, a huge benefit. HO's know what the cost is and we guarantee that price. Most other electricians here base their price on how busy they are! Being we specialize and advertise for this type of work, we do more k&t than anyone else in town.


Funny. NOBODY installs K&T these days.


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## jarvis design

Haha, you're a funny guy sparky!


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## 480sparky

jarvis design said:


> Haha, you're a funny guy sparky!



You actually install K&T?


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## jarvis design

480sparky said:


> You actually install K&T?


Uhmmm, NO, we re-wire houses that have k&t....
Of course that's when we're not busy installing galvanized piping for homeowners that want their copper removed! Lol


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## Inner10

hdavis said:


> A few more notes...
> 
> Each one is different, but if it's still all plaster and lath or drywall over plaster and lath, it usually takes 2 hrs per device through device out for experienced crews. A lot of places you don't have to remove all the old knob and post, just as much as you can reasonably access, so that saves some time. If the people patching are really bad, the obvious key is to make it really really easy for them. If it's drywall over plaster and lath, use a 6" hole saw through the drywall, then 4" through the plaster and lath - it gives the patchers a very easy patch to do. It helps if you screw the drywall piece you took out to the wall near where it came out - the patchers can just bevel the edges and put it in. You can do something similar with the plaster and lath, just going through the plaster with a 6 inch, then through the lath with a 4", but that's really coddling these guys. Try to keep them at least 2 inches from any trim or corners so the patch can be blended. There isn't any secret to taking out existing boxes - a lot of damage can happen there with a sawzall, but there isn't much choice. A metal cutting blade is less likely to hook onto the lath and pull it off the framing.


2 hours per device for an experienced crew is pretty high. But then again one device is 10 min the next can be 3 or 4 hours. 

If I have to patch I make the hole clean, save the piece and screw it back into the wall to make the painter's life easier. 

Sawzalls work fine but you can take a whole ceiling or wall out with one they are so aggresssive. If you can see the nails through the box buzz them out with a MultiMaster then a few small taps and it's done. If you can't then bang and pry it till you can.

The multimaster was made for plaster, cut a grove with the grinder blade, then continue the cut right through with a metal blade, perfect hole in plaster.


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## hdavis

Inner10 said:


> 2 hours per device for an experienced crew is pretty high. But then again one device is 10 min the next can be 3 or 4 hours.
> 
> If I have to patch I make the hole clean, save the piece and screw it back into the wall to make the painter's life easier.
> 
> Sawzalls work fine but you can take a whole ceiling or wall out with one they are so aggresssive. If you can see the nails through the box buzz them out with a MultiMaster then a few small taps and it's done. If you can't then bang and pry it till you can.
> 
> The multimaster was made for plaster, cut a grove with the grinder blade, then continue the cut right through with a metal blade, perfect hole in plaster.


I agree with all this. I didn't go into the the way I cut in for boxes with a multimaster because he's only doing the electrical, not the patching. Switching to a metal cutting blade is just to prevent massive patches that the repair guys they seem to have wouldn't be able to handle very easily. There are few things worse than having plaster and lathe so broken up you can't get an old work box to hook in solidly. When I've had to deal with this, the quickest solution is to use fire foam, and foam the box in solid so it can't move. If I have to do a patch on the wall around the box for cosmetic reasons, I'll do the first deep fill around the box with Durabond with acrylic modifier to it will stick to the plastic box (modifier not needed for metal).

If I'm doing the all cuts and the patching myself, I'll use a multimaster and a rectangular template, so most of the patches are the same size and rectangles are faster to patch than circles. The few times I have to trench I screw a guide to the wall and use a $20 circular saw with a demo blade. Gives a pretty neat trench to patch. Lots and lots of tricks...


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## hdavis

OOPS! Looks like Cwat is doing the patching, too. By all means, do everything with a multimaster or similar tool. Nice neat rectangular holes - it doesn't get easier than that. I'd still trench with a circular saw if you had to do a horizontal trench. 

If his guys aren't experienced in fishing old houses, they may be better off doing more horizontal trenches than you or I would. Tough to say without seeing the house...


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## cwatbay

Thanks for all the advice. We (I) finally finished this house. I went ahead and did the house myself, since I knew it would be a PIB and I didn't want to have extra workers out there having to deal with this. 

Nonetheless, the HO didn't want any patching or painting, even though it is written into the contract that channeling, patching, painting would be necessary in this type of work. He definitely wanted to use any other method to avoid cutting into walls to fish wire ( ie: cutting holes just for fishing wire and not for additional outlets and switches). This HO is also in the "housing" business, being an appraiser. 

There were definitely some holes, in which I put the cutout drywall back, secured it, then patch the seams. I don't sand it, I don't paint it ---- that is made clear to the HO. Do I sometimes sand it down, yes --- just not this time as the HO said he would do. Also, if you want me to keep costs down on a project, then we agree that little things that take time and money will be either done by you (The HO) or another contractor. 

The other factor is the cost of extra help on a job. If I have bring in one of my electrical contractor partners or one of my associate contractors, then the cost for the HO goes up (substantially). If the HO wants to help with simple things (i.e. things they can actually do proficiently) like helping to pull wiring in certain locations, finding the glow rod or chain, turning off a switch or breaker, then that's ok ---- that means I don't have to bring someone in to do those types of things (i.e: low end helper stuff). 

On this job, I had to be particularly creative with fishing wire, transferring circuits from one sub-panel to another (one in the basement and one in the garage) so that the newer panel would have the available and lower cost GFCI and AFCI breakers. I also had to consolidate bedroom, living room, garage and bathroom outlets (on different stories of the house) to be on GFCI circuits which made some kind of logical and code compliant sense. 

Another factor was that the previous owner of the house was an airline electrician who figured he could do it all himself ----- which meant I had to find all the assorted "remodel type" splice boxes he had in the attic for running Romex from the panel-- to the jbox -- to the KT --- all of which were hidden in blown-in insulation. 

I am going back today to cleans things up and get everything ready for inspection --- like labeling all the circuits correctly --- which they weren't when I first arrived.


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## hdavis

That's great! How does the HO like it?


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## Inner10

> The other factor is the cost of extra help on a job. If I have bring in one of my electrical contractor partners or one of my associate contractors, then the cost for the HO goes up (substantially). If the HO wants to help with simple things (i.e. things they can actually do proficiently) like helping to pull wiring in certain locations, finding the glow rod or chain, turning off a switch or breaker, then that's ok ---- that means I don't have to bring someone in to do those types of things (i.e: low end helper stuff).


Been there done that never again! If its a 2 man job get another man.


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