Is spray foam insulation OK under concrete in basement instead of XPS?
I’m having my existing basement waterproofed (hopefully!) and insulated, and having a concrete floor poured in place of the present moist gravel. My Energy Advisor / insulation guy suggests continuing the spray foam we’ll be applying to the walls, on down onto and over the prepared (and drained) gravel under the new concrete, and having that serve as both the waterproof and insulating layer. I haven’t read of anyone doing that. The alternative is blueboard (I’m thinking 1″ is plenty) and vapor barrier (Tenoarm poly with sealed seams). So, is it OK to use only spray foam under the concrete?
Also, if I use the blueboard (that’s XPS, right?), does the vapor barrier (Tenoarm) go below the blueboard or above it? My understanding is that the layers would be gravel, Tenoarm, blueboard, concrete. Please confirm!! Thanks.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part