Foundation in Cold Climate

[icgitar]

Hi there!

I am planning on building a Pompeii oven in Maine and would like some input on how to improve frost heaving in the foundation. Can I have suggestions on how to pour the concrete to prevent this?

I do know that rebar supports can be there to help. How deep should I make the foundation and is there special footing needed?

Thanks!

IC

[mongota]

The obvious and safest answer answer is to put your footings at frost depth. I'd venture in Maine that might be at 48"? Here in CT I'm at 42". A standard below-grade footing and foundation wall will perform fine.

If heaving is a serious concern due to your soil conditions, then I'd do that at a minimum. Even at frost depth, you can further decrease the likelihood of heaving by adding, for example, 2" thick rigid foam board insulation against the foundation wall before back filling, so the RFBI will be sandwiched between the foundation and the soil. While the soil may still freeze and expand, the foam board can act as a slip sheet of sorts between the frozen soil and the foundation.

Ovens on the whole have a pretty high load in terms of lbs per sqft that bear on the footing. I think when I rough calculated mine, the load on the footings was around 550 lbs per foot.

[icgitar]

@ Mongota:

Thanks so much! This is very helpful. So the way I'm understanding (please excuse the naivety) - Making a concrete slab with footing is essentially just a perimeter of slab being deeper than the main platform foundation, which in my case, hypothetically, would be 48" deep?

This makes sense - I would think adding rebar to the foot itself would be helpful.

Thanks,

IC

[mongota]

icgitar If you look at my build, a link should be at the bottom of this post, near my signature...I have some photos of the below-grade work. Likely on Page 1 of my build.

Where I built, my subsoil drains very well and there is little to no clay (clay can hold moisture and expand/contract with moisture levels) in my subsoil. So I felt VERY comfortable not going to complete frost depth. I went maybe 30" deep. I formed the footings up, then poured the perimeter footing. On top of that footing I laid up a few courses of CMU (concrete block) to get me to grade. Then on top of that CMU I installed some rebar, then poured my slab-on-grade. Actually, slightly above grade.

That got me from below grade to above grade. I looked, and those photos are indeed on Page 1 of my build, scroll past the first few posts and scroll to Post #10 on Page 1. Hopefully those pics will help a bit. My way is NOT the only way, so others will chime in as well. And certainly ask any other questions if you have them! But I hope the pics will explain the footing/stem wall/slab part of the build.

Hope that helps!

[Baza]

Hey IC,

Congrats on your start to the building process! Sorry I'm chiming in late to the game on your question.
mongota has helped scores of builder in this forum - including me!
So you may be off to the races already ...

Just to give you a visual - on my page the first 5 posts are devoted to what Mongota was referring to with the Rigid Insulation below grade.
This is what I did. Here in Ontario - getting frost deep like you is a thing (though I found bedrock about 36" down so stopped there.
We built a wooden form that we left in the ground to surround the rigid foam form that served as the walls for the foundation pour.
Plenty of rebar and it was sorted.

I hope this helps in your efforts!
Best of luck on your build!
Barry