Minimalist on top of slab insulation options
I have an existing 1970s structure with a 42″ below grade basement slab. I’m re-doing the flooring in the basement (settled on cheap laminate over expensive stained and polished concrete) and am wondering about getting a tiny bit of insulation on top of the slab before I install the laminate.
I have a 91″ ceiling height. so I don’t have the head height to consider any of the lovely options described in the lovely GBA q&a here such as 2″ of XPS and an inch of plywood.
Additionally, because my water table is quite high, I’m very reluctant to put down plywood/OSB etc. anywhere near the floor. Yes, I’ll likely have to chuck the laminate if it gets wet but flooring choices are tough in this scenario. I’m less willing to chuck the rough system.
So I was wondering (here’s the bad idea):
Why can’t I just put the laminate on top of xps?
So my system would be something like:
polyE or taped laminate underlayment?
1″ XPS (or should I use a different foam)
4″ concrete slab (could epoxy seal it for vapor control)
That’s a finished floor height of ~1.5″ and an R of ~5.5. That’s about half of the desired R-10 but a lot better than the R-0.5 to 1 the floor and underlayment alone would provide.
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