Gearing up for Hydronics - Under fill question

[BTI]

First off I'd like to say you have a great forum here.
I've read alot before joining and more after LOL
Sorry this post is so long.
I have some pics to show my problem. They are from when it was built.
It now has fill in it but the fill doesn't touch any outside walls.
We had the garage built 2 years ago. It is 28x40x12.
We are going to use hydronics for heat.
My problem is where we built it could not be built up. So all fill has to go inside the building.
There is a creek that runs behind the garage.
So now I have a garage that needs fill, we ordered "fill material" from a local sand and gravel pit.
Looks more like sand than anything else.
The back side is approx 36" from where the slab will be to the normal land contour.
I need to seal off the bottom of the boards to keep any water from getting in "Just in case" the creek ever did come up enough to erode the sand under the slab to be poured inside the building.
Looking for ideas of what to do.
I've read that you want to keep as much outside temps off of the concrete for alot of different reasons.
I thought of framing in the posts then filling the void with concrete, sort of a poured wall.
Then push the fill against the poured wall
What do ya's think?

Thanks in advance.
BTI

 

[Synergy]

Sorry I cant answer your question.

Though I am curious where you are and if they allow enclosed structures to be built with pressure treated posts into soil? Not trying to knock your project, just looks like very unconventional (modern) construction, except for the truss roof, which appears to be 8' OC.

 

[BTI]

It's a pole barn.
We are allowed to put treated posts into the ground they are in concrete.
I did not build the structure it was built by a builder in the area that has been building them since 1972.

Thanks

 

[jklingel]

I'm not sure I follow what your question is (Ask my sister; I ain't the shiniest apple in the tree....), but I do know this. You need a good vapor retarder under that slab (at least 6 mil visqueen, maybe 8, and (Google) somebody makes a 15 mil membrane that is supposed to be "the stuff".... just ask the sales guy, right?) You will also need at least 2" of XPS below the slab, on top of the vapor retarder. Plus, and most important, 2" to 4" of XPS at the edge of the slab, if at all possible. Everyone clearly says that the heat lost out of the edge of the slab is the killer. Now for the creek. If I understand, you don't want external water getting into the slab via the walls. On ICFs, a very heavy membrane called "bitchathane" is commonly used here; call your local ICF guys. Myself, I would also consider filling in around the garage and, several feet from it, installing a water retarding membrane down several feet and filling on both sides of it. If you are filling inside the building before pouring the slab, you will, of course, be compacting every 8-10" of fill, and you should be simultaneously compacting the same depth outside or you may push your walls out. Hope that helps. j