arw01 wrote:
Radiant heat shop floor:

Top soil has been removed
very hard base ground (use a breaking bar to be able to dig in it)
3-7" of 3/4" crush gravel

moisture barrier HERE?

2" polystyryene extruded foam insulation

moisture barrier HERE?

concrete reinforcement mesh
1/2" pex heat tubing
4" concrete with plasticizers and fiber reinforcement

Everyone in the businss has a different opinion if it's below the foam
or on the foam.

Concrete engineer says on the foam
radiant installer says below the foam.

Alan

I'm not sure what the correct answer is. Under the insulation I
suppose there is a risk of getting holes in the barrier. Above the
insulation and you now allow moisture up around the insulation closer
to the floor. I do know this though.... I have radiant floor heat in
my basement and you are going to LOVE it!!!! My wife and I were in
Atlanta when the floor was done so I'm not sure where the plastic is or
even if there is any at all. (monkey boy contractor, as my wife likes
to call him) We've never had any moisture problems.

Bryan