Building a floor structure on helical piles
Hello – looking to get some advice on a general direction for my floor build.
I’m building an 8×12, freestanding office on top of helical piles. I’m in Ontario Canada (zone 7), so cold and wet weather is a concern. I’ve found 2 or 3 posts on this site with mostly the same advice, but I’ve been given supplemental suggestions and want to see if they fit.
I have put down a gravel base and it was suggested that I fill the void between the gravel and the floor joists with foam board insulation. The logic here is foam is used in concrete floor construction. I’m not sure how sound this idea is. I’ll skirt the outside of the building, but the foam will still be exposed to the elements to a degree. The foam doesn’t take the load, but does need to be tight to the bottom.
As for the floor, I’ve read here that a mix of foam and traditional insulation is a good approach. I’m thinking that the sandwich will look like (top down)
-2” foam insulation
-1/2” PT ply
Is this correct?
I came across some suggestions on putting an air gap in there, but it sounds like that might be a bad approach?
Does any sort of house wrap (tyvek) make any sense for the ‘sandwich’?
And I realize the floor will never really be “warm” without some sort of floor heating system. I just want to construct something that’ll keep the moisture out and follows best practices for efficiency.
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