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Thickened slab with 300 psf load – will 30 psi rigid foam support that?

idahobuild | Posted in General Questions on

Our slab on grade home has a thickened slab under a load bearing wall ( about 8 feet long).  Rigid foam will be placed horizontally under the entire slab. 

The GC is specing out 30 psi Amvic, Ampex foam. Based on a psi to psf calculator; that is 4,300 psf . Even if derated by a factor of  5, it is about 864 psf.  When I asked the engineer he says the load is about 300 psf on that part of the slab. all seems good.

Does my math jive? Does this 30 psi foam seem like it supports that load?

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  1. Expert Member
    Michael Maines | | #1

    Yes that should be more than enough for your situation.

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