We've done several exterior driveways and courtyards in commercial areas with high density foam products in contact with soil, under concrete and paver driving surfaces as specified by engineers, mostly in Ontario and Colorado.

Of course flatwork is fine, as long as you're using extruded and not expanded. But footers under concrete walls is a whole 'nother bucket of beans.

Q , you've probably checked out Legalett.. its slab form or "edge element "as they call it, is wire cut expanded type 2.
And they are stacking 2 floors of ICF above on them regularly.
We can get some sweet EPS high density locally which has been spec'd for road bulding fill.
I haven't used EPS under footings yet, but the Highgrade stuff looks good. Very high psi rating.

Eric, we discussed Legalett just above; I don't have time to study it, but don't really trust it.

Q, I respect your opinion. Legelett is EU technology come to Canada. I'm watching too. LOL

I'm sure some, most or all of you don't like what I've done in Seward, Ak, but it's done. I put 2" of R-tech under the slab and footer, 6" slab, 12x18 footer with rebar, with mesh fiber and pex.

One thing I did that worked out really well was to foam the indvidual foam boards together with a little foam gun, they just felt better when I walked on them.

I also put 2" of R-Tech on the inside of the forms and it stayed with the slab when the forms were stripped.

I put 4' of 2" R-tech around the perimeter of the slab butting up to the vertical foam to keep the cold away from the slab.

When something cracks or falls down, I'll be the first to know!

Toothy

Which R-Tech? Density? Under an ICF wall?

OOOPs!!

I used the light R-Tech.

I forgot after getting through all the pages in this post, I am in the ICF section,  I'm going to use sticks or those foam and osb walls.

Sorry for forgetting that I'm in ICF's section.

I was going to use a 2 course ICF kneewall but have decided against it. This is for a shop the main house may be full ICF or ICF-SIPS, depending on what I find out about the SIPS verses ICF argument, but we don't need to start that one up again here.

Toothy

You're not in too bad a shape without the weight of an ICF wall.

But which R-Tech? Plastic-coated, foil-coated, or fold-out? Density?

It had an alumanized side and a plastic coated side, the alumanized side didn't like the cement. You would think they would put the aluminum inside the plastic film.

I don't know the weight, it's kind of burried! It was 4x8 sheets with a center snap line. It was just what they had at the lumber yard. When I stepped on it it left a very slight impression.

I did use the unfaced high density sheets under the garage door entry as my perimeter insulation, I figured the squishy stuff might not get along with the back hoe.

I have driven around on it with a Cat 416 and it hasn't cracked at all and it was fairly green, 2-3 weeks.

Toothy

 

Sounds like you used the R-Tech BG, with the foil liner. Density is .9x, which is not good for footers. I don't even like it that low for flatwork, but oh well they make it. 1.5x-2x is best, but still not for footers under an ICF wall.

You won't have a problem with the flatwork because it distributes the load with the help of the remesh. But you do put millions of cracks in it when you drive on it less than 28 days. Coating the foil with polyethylene would defeat the purpose of reflecting infrared.

Using unfaced EPS is not a good idea for ground contact because it's water-permeable, 1x density being 3%. It can get water-logged over time. Hopefully you have a vapor barrier under it.

guy's ....

http://oikos.com/esb/40/polyform.html

hard to be more insulated than that....