VERMICULITE in the foundation?

[Calabrese]

HI, my name is Joe and I am about to start my pizza oven build. I live in Canada, Mississauga to be exact just outside of Toronto. Frost is a big concern here because of our winters and I really don't want to dig four feet if I don't have to. I'd like to dig 16" trenches around the perimeter along with 6 to 8 - 8" sono tubes about 4' down. I'm putting down gravel, 6mil poly and mybe some 2" foam. My question is this has anyone ever put a 3 to 4" layer of the vermiculite and cement mixture before the 5.5" foundation slab? Your thouhts would be appreciated. This site is amazing and has already answered a 100 questions that I didn't have to ask.

[karl]

Re: VERMICULITE in the foundation?

Hello Joe,
Based on what I saw and experienced when I used a cement/perlite mix as part of the insulation under my oven I will not recommend to use this under the foundation slab. Even though the pressure may not be much higher than under the oven itself i really do not think that the structure of the cement/perlite(vermicullite) will survive the continues freeze and taw (thaw?) and other erosion mechanisms in the ground (water etc). The standard way of making a ground slab foundation "frost-free" over here is to make sure you have some 40 cm of gravel, then 7,5-10 cm of styrofoam insulation (specified for high pressure) which extends some 50 cm outside the foundation perimeter. Some put the styrofoam insulation in the bottom (takes some more digging due to the extension). And on top of that the reinforced foundation slab.

karl

[Calabrese]

Re: VERMICULITE in the foundation?

Thanks, Karl thats basicly what I have done accept I did dig 9 8" sono tubes 4' down and then tied everything with rebar. I have pictures but I havn't figured-out how to post them YET, I'm working on that, and will post them soon. Thanks, Joe