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Any compression issues with 7″ of EPS?

Scot69 | Posted in Energy Efficiency and Durability on

Thanks for the previous advice, One more, I have EPS with backing material in my area at 1″ thickness only it has 10 PSI rating. I want to place 7 layers,is compression a facter in zone 6 with reboard and rubber thanks

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  1. GBA Editor
    Martin Holladay | | #1

    I'm not sure what you mean by "reboard and rubber."

    If you are talking about a floor, you might want to read this article: Foam Under Footings. I also advise you to read the comments below the article.

    The article notes, "Engineers explain that good soils should be able to support 3,000 lbs. per square foot (20.9 psi). As it turns out, common extruded polystyrene (XPS) insulation like Dow Styrofoam or Owens Corning Foamular has a compressive strength of 25 psi. That’s more than many soils that are routinely used to support a footing and a house."

    Your 10 psi foam is not as dense as the foam discussed in that article.

  2. Scot69 | | #2

    This is a roof application-reboard is a acceptable underlayment for EDPM? rubber roofing

  3. GBA Editor
    Martin Holladay | | #3

    I don't think there should be any problems from using EPS insulation above your roof sheathing.

    Concerning your question about an acceptable underlayment for your EPDM roofing, that question should be directed to the EPDM manufacturer.

  4. Expert Member
    Dana Dorsett | | #4

    Type-I EPS is very commonly used in roofing applications, but you can't walk on that roof without something above the EPS to distribute the weight or you'll permanently dent it with your boots. That's is why EPS products manufactured with fiberboard or other stiffer backers are available- it improves the walk-ability of the roof.

    Different roofing materials may require a slip-surface layer between the roofing an the EPS or backer to function without undue stresses to either/both. If your 1" EPS has a very thin facer meant to be a slip surface rather than a stiffening backer you may have to tread lightly up there.

  5. jinmtvt | | #5

    Best product for that up to now was firestone HD-Recover boards
    Fiberglass facing on both sides of a 0,5" polyiso ... but with the recent information
    about polyiso performance at sub 0c temps ... the price is not soo good anymore.

    Most EPS roofing companies offer HD EPS with a specific fiber board of some sort, usually alsphalt adhered on top of it.

    If this is for EPDM installation , the type of installation will change the requirements of the substrate substantially.
    Ballasted? fully adhered? fastened ?

    have fun, but dont mess it up ! ($$$ )

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