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Is there any suitable way to install/support stone veneer over 2” continuous exterior foam insulation? The GPS foam I’m planning on using is 25PSI and the wall is 2 by 6 on 24” centers with OSB Sheathing. The stone I have picked out is 11 lbs per square foot.

dasrks | Posted in General Questions on

Stone veneer over 2” GPS  foam board installation.

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  1. Expert Member
    Peter Engle | | #1

    We need a bit more information. You don't mention whether this is going to be an anchored veneer or adhered veneer. Anchored veneer rests on a brick ledge that is either part of the foundation or attached to it, with the ledge bearing the weight of the veneer. Adhered veneer is installed on a stucco base, with the stucco and metal lath supporting the weight of the veneer.

    If this is anchored veneer, there is no problem with using foam behind it - the brick ledge just has to be wide enough to support the veneer outside the foam insulation.

    For adhered veneer, the IRC provides prescriptive requirements for fasteners over foam in Table R703.15.1. Unfortunately, if the stone weighs 11 psf, you've got to also add a few psf for the stucco base and bedding mortar. That bumps you up into the "25 psf" column and the thickest foam allowed for any fastening is only 1". Beyond that, design is required. This means that a local engineer/architect must design the fastening system based on local seismic and wind conditions.

    1. dasrks | | #2

      Thank you

  2. Jon_R | | #3

    Consider moving some or all of the foam to the interior side.

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