Pulling Wire Through Spray Foamed Walls

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Greg H

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Location
Durham, NC, USA
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Electrician
Had a job the other day where a customer wanted me to install a single GFCI receptacle. It was a sight unseen job for a customer that I had worked for before, so, I was billing on a time and material basis. Simple enough in theory, but when I got there and started investigating turns out the wall that they had initially wanted the receptacle in was filled with spray foam. I found this out by doing a wire probe test of the area they wanted, so, I didn't do any significant damage to the wall; but it also felt like there was some kind of blocking in the wall as well (lesson there: always do a wire probe test before making cuts in a wall that you didn't rough in yourself, and even if you did, still not a bad idea). Fortunately, there was an adjacent interior wall with hollow wall cavities and I was able to convince the customer that that would be a better location for the receptacle, so, it didn't end up being a problem, customer just has to spackle and paint over the probing holes that I made.

However, been thinking about what I could have done had there not been an equally suitable empty wall cavity nearby. Has anybody figured a good (read: economical) way to pull wire through existing spray foamed walls? The only two ideas that I have thought of wold be cutting out a pretty big panel(s) of sheetrock and carving a big enough notch in the foam to bring my wire through or using a flexible drill adapter to try in bore a channel in the foam, but neither of these seem like particularly good ideas for a number of reasons (time, risk of damaging anything else that is in the wall, compromising the thermal properties of the spray foam, customer will have to repair a lot of sheetrock, I could go on). Has anybody figured any good tricks for this? Thanks
 
I like your idea about a long drill excavating a hole behind the sheetrock. I don't think there will be significant harm to the thermal properties. Your concern about unknown 'things' in the wall cavity is the only drawback I can think of. Shouldn't be much sheetrock damage, just the holes at the top of the cavity and the location for the new outlet.
 
I would not want to hit anything. I would just slice the sheetrock. Down side to Sprayfoam. I have my wall done in spray foam if if I have to get in that wall Sheetrocks getting cut.
 
I'm with ac\dc, if the HO is patching I would cut a groove in the Sheetrock for the cable and remove a minimum amount of the foam material enough to allow the cable to be behind the rock. Why risk drilling into something hidden in the wall.
 
infinity said:
I'm with ac\dc, if the HO is patching I would cut a groove in the Sheetrock for the cable and remove a minimum amount of the foam material enough to allow the cable to be behind the rock. Why risk drilling into something hidden in the wall.
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I think you're assuming a painted wall, not the wallpaper mural that's been in place since the 1920s... (yes, that would probably be plaster and lath).
 
Spray foam isn't too dense to go through.
A piece #4 bare solid, bent to the right curvature, can go 4 feet.

Then bend a tight loop in the ass end, strip the sheathing off the Romex, hook it through the loop on the #4, tape it up and pull it in

🤷
 
James L said:
Spray foam isn't too dense to go through.
A piece #4 bare solid, bent to the right curvature, can go 4 feet.

Then bend a tight loop in the ass end, strip the sheathing off the Romex, hook it through the loop on the #4, tape it up and pull it in

🤷
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How about a piece of fish tape on a drill?
 
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