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I was wondering if anyone knew the minimum required thickness of concrete/gypsum in a Hydronic wet installation over a basement slab?
Also I'd like to know if pex should be used or a more rigid tubing?
According to the pex mfgr Stadler-Viega site below, they specify a slab at least 3 1/2" thick over poylstyrene insulation boards with reinforcing steel mesh, the pex tied to the mesh, with a minimum concrete coverage of the pex of 1".
Also Google the Universal Building Code: "UBC Section 1906.3.10" & check with local building inspector for any local variations.
I believe instillation over a pre-existing concrete floor is 1½" and in IMHO Pex would be the best choice. For minimal thickness you might consider Fig. 2 page 3 of the link that Jacktheshack provided.
The UBC code, according to Stadler indicates a minimum slab thickness of 3 1/2" for slab on grade systems; the 1 1/2" noted in 1906.3.10 refers to the amount of coverage over the PEX element.
The code also allows for thin-slab systems of 1.5" for residential wood-framed floor decks that would not support the weight of a 3 1/2' to 4" concrete slab.
These often include gypcrete & other light weight concrete products.