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Which comes first? Cable or insulation?


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05-16-09, 06:00 PM   #1  
Which comes first? Cable or insulation?

The wall I'm insulating and installing cables on does not have studs. I will not be putting studs into the wall either. Instead, I have some 2" thick interlocking polystyrene R10 insulation boards which you screw to the wall with masonry screws, through an aluminum furring strip. So no studs will be required. The drywall or concreteboard will be screwed directly onto this insulation, I suppose also by attaching it to the brick, through the insulation, with masonry screws. I'm not actually sure..

I'm trying to figure out what the correct order is. Do you install the electric cable first or put in the insulation and then somehow run the cables through it and install the electric boxes over the insulation? Either way, it's complicated.



As you can see, I've already installed the electric boxes where they are supposed to go. Don't worry, the breaker is off. I won't turn it back on until I have finished installing the lights. Those cables are not carrying any current right now. I had to run the cables because they have to be in before the insulation, or am I wrong? How do you install the insulation over the cables though? How am I supposed to cut ridges in the back of the insulation and somehow get it exactly right so the cables fit in the ridge? And of course, I don't know how to cut holes exactly the right size and in the exact right place for the wall boxes and the cable connectors. Maybe if I had x-ray vision, I could do it.

Also, how do you protect the cables from screws which you will later be screwing into the wall to attach drywall/concreteboard, shelves, mirrors, etc? Those metal protector things are only useful when the cable is going through a notch in a stud. They will fall out if I try to use them on pink insulation. And even if I used the protected cable that you see on the outside of walls, I'm going to be drilling holes with a drill. These bits go right through metal and brick, so why wouldn't they just go straight through shielded cable? How can I avoid drilling through the cables when I can't see where they are?

 
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05-16-09, 07:01 PM   #2  
Hi DZ, I'm glad you got to the problem at the end of your explaination. Protecting the wire is one of the big issues and it is something you want to do right. I'm going to pass on giving my opinion as the pros will surely go beyond what I would say. Good luck with your insulation,

Bud

 
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05-16-09, 07:19 PM   #3  
Posted By: Bud9051 Hi DZ, I'm glad you got to the problem at the end of your explaination. Protecting the wire is one of the big issues and it is something you want to do right. I'm going to pass on giving my opinion as the pros will surely go beyond what I would say. Good luck with your insulation,

Bud
Yes, and even if I can guess their location correctly and avoid them, what happens if the next owner, or a tenant, hammers a nail or screws a screw into the cables? They aren't going to have a picture in their head of where the cables would be.

Should I put them somewhere else? Impossible, that's where the lights are going. It took me months to plan it out. The mirror will go in between them. The sink will go below. It's a small bathroom and there's nowhere else to put anything. If I change one thing - you can't isolate anything - it affects everything else. One little change means the introduction of a whole new set of problems that then have to be worked into the planning. You just shift the problem somewhere else. More time, money, gone.


Last edited by doublezero; 05-16-09 at 09:13 PM.
 
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05-17-09, 06:16 AM   #4  
Sorry DZ, I didn't notice you are in the wrong catagory. You need to re-post this in the "Electrical AC-DC". That explains no comments.

This time of year the insulation talk goes dead and the mods rarely visit. Maybe a Mod will shift this over, please.

Bud

 
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05-18-09, 12:42 PM   #5  
wire after, in conduit

Yes, the best advice is to post it in the AC-DC forum and the pro's will help.

I'm not a pro, but I've been thinking about doing something similar. For those outside walls with furring strips, I would do the wall first, then surface mount everything, with the wiring in conduit up to the ceiling. It's not as nice looking, but it's a basement: if you want it to be as nice looking as the rest of the house, use full size framing.

 
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05-18-09, 10:46 PM   #6  
Posted By: wgc Yes, the best advice is to post it in the AC-DC forum and the pro's will help.

I'm not a pro, but I've been thinking about doing something similar. For those outside walls with furring strips, I would do the wall first, then surface mount everything, with the wiring in conduit up to the ceiling. It's not as nice looking, but it's a basement: if you want it to be as nice looking as the rest of the house, use full size framing.
This reply is to both you and bud9041.
I would move the post but I don't know how to do that and my question is about both electrical and insulation. Also, I found some instructions that came with the insulation showing that you are supposed to put the insulation up first, then cut holes for electric boxes and cables. They are supposed to go at the front of the insulation, not behind it. You attach the electric boxes to pieces of wood which you attach to the brick. I didn't know that, and used the deepest electric boxes I could find, hoping they will match the thickness of the finished wall. Unfortunately I ran out of time and put the insulation up after the electrical. Then later I found these instructions lying on the floor, covered by insulation, tools, garbage bags and other supplies..
And since it's a bathroom not in a basement, conduit outside the wall isn't appropriate even if it would be functional. One would hope that future residents will have the common sense to know that there are going to be cables somewhere inside the wall, very close to where these light fixtures are. Because where there are light fixtures, cables can't be far away.
In hindsight I could have framed the wall with 2x4s and insulated between them. Either way, I lose 2" of area in the room. But I have never done this before and without any experience to base it on, just trying to assimilate as fast as possible all this information I'm going through, and not make mistakes, I allowed myself to be convinced that these pink boards and furring strips would be faster, easier, cheaper, and better. They're none of the above. The only benefit is not having to put up a vapor barrier because the pink board acts as insulation and a vapor barrier.

 
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05-19-09, 04:30 AM   #7  
DZ, I can answer your insulation questions, but the board is very much concerned about safety, ie the electrical needs to be done right. GFCI's, conduit, and other issues I am not qualified to comment on. There are several very qualified posters on the board, bud they don't watch the insulation threads. You don't have to move this thread, just start another over there with your pictures. Nothing else has been stated over here that they need to consider except what you posted.

After you have the electrical issue resolved, then the insulation is easy.

Bud

 
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