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Does anyone make a barbed fastener specifically made to fasten a sheet of foam to another sheet of foam?

rocket190 | Posted in Green Building Techniques on

I have an attic knee wall area that I’m insulating with reclaimed 1 lb eps sheets. I ha e hundreds of sheets available. I’d like to use cap nails to secure the first layer of foam directly to the knee wall studs. I would tape foam seams. Since I have a large amount of sheets available I would like to apply 6-8″ of foam to the exterior. Is there any device like a push pin that is designed to fasten subsequent sheets of foam to another? Since the foam is non structural it just needs to make a tight connection and maintain grip to the other sheet. This would hopefully be cheaper and easier than trying to hit studs with expensive 8″ screws or expensive and hard to find 8″ cap nails.

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  1. Adam Emter - Zone 7a | | #1

    Have you considered a polyurethane foam adhesive? Great Stuff makes some and it bonds really well, in my opinion.

  2. rocket190 | | #2

    I haven't tried that product yet. Will it expand enough to cause gaps between the sheets? Also, even if that works it would be nice to have some cheap mechanical fasteners to hold the sheets together until the adhesive is cured.

  3. GBA Editor
    Martin Holladay | | #3

    I would use some foam-compatible adhesive, and a minimum number of fasteners (long cap nails or screws with fender washers).

  4. peaceonearth | | #4


    Longer cap nails could work for a couple of layers of foam, but you would have to keep each layer supported for taping the seams. I have used the adhesive ( with a gun) and it works well, although my application was for one layer of 2" foam on a concrete wall. The sheets adhered flat to the wall, so I didn't note any expansion that was problematic.

    Won't you need furring strips and long screws anyway after the final layer of foam? This could/would be the substantial source of holding up all the foam, even though you would need an interim source for each layer.

  5. Adam Emter - Zone 7a | | #5

    Rick, that Great Stuff adhesive foam will not expand once you have pressed the foam sheets together. It flattens out and holds very well once the adhesive had begun to dry. If it was me, I would use that foam and then install two screws with washers into the framing. Done deal.

  6. rocket190 | | #6

    Thanks for the tips/advice. I will definitely try out the Great Stuff adhesive. It sounds like a good solution. While I could install furring strips after foam, it's technically not needed since it's an inaccessible knee wall area. My only concern about lack of solid sheathing would be ifnrodents ever got in that area they could easily chew through the foam.

  7. peaceonearth | | #7


    Mice can get around thru tiny spaces (squirrels less so, but smaller places than you might think). It is difficult to imagine that you can install solid sheathing in such a location that would entirely preclude mice. And since, as you say, this is a protected area with no (human) activity, sheathing in my opinion would be a waste of money. At least this way you might see any rodent activity.

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