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Taping Two Layers of EPS Foam Beneath Slab

tsloss | Posted in General Questions on

Planning on 2 layers of 2″ EPS foam under my slab. Is there a good way to secure this together? I’m not sure how well tape will hold the joints together and/or what kind of tape to use. I will stagger the joints as well. Is there a good way to glue the layers together? I’ve seen some say that cans of spray foam work well, but I have concerns with even expansion and proper adhesion. Are there better glues to use, and how much would you recommend per 4×8 sheet? I’m OK with taping the joints and gluing, but I want to make sure it’s effective. No sense taping all the joints if the tape doesn’t stick; and I don’t want to use too much or little glue. Any advice? Thanks in advance for any help provided.

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Replies

  1. GBA Editor
    Kiley Jacques | | #1

    Your question is addressed by a few GBA experts in this thread.

  2. tsloss | | #2

    Thanks. The thread didn't really help me too much. Some said tape both layers, some not. Nothing about what kind of tape will stick, and no information about adhesives. More info would be appreciated. Thanks.

    1. ssnellings | | #3

      If you have a separate poly layer under the slab there isn't much of a point to taping and it's a bunch of extra work. If you don't have a poly layer, might as well tape it and get it right.

      There are probably a lot of adhesives that will work, 3M 78 is a good place to start. 3M also publishes usage information on their website which likely will contain some information on coverage recommendation. You're really just looking to keep everything in place until the concrete gets placed, so perfect coverage shouldn't be critical.

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