Drainage mat below basement slab, to replace stone
I tore out my damp musty basement floor, and we have excavated down 16″ to gain some head room, and install 4″ foam, below the new slab. I would typically use 4″ of gravel as the base, but am trying to find information about the use of drainage mat, or soil gas mats instead (to save labor and head room).
I realize the stone serves two purposes (capillary break and air space for soil gas control). The sales people I have talked to from a drainage mat site, says I would just need 12″ of it around the perimeter, but I was thinking I would need it under the entire slab (to replace the stone).
So I would potentially lay this drainage mat all around the perimeter (right in the sand), with a 4″ t fitting for soil gas exhaust pipe, then lay 4″ of foam, then 6-10 mil plastic over the foam (for extra air sealing of radon I hope), and then the new 3-4″ floor.
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