Foundation and a cold Canadian winter

[ekah]

Hi there, I'm new to this site and am looking for information on how people have done their foundations to deal with frost problems. Thanks

[dmun]

Re: Foundation and a cold Canadian winter

There are two approaches. You can dig down under the frost line, pour heavy footings on bare soil, and build up from there. This is what you need to do if your oven is part of a building which needs to conform to building code for masonry fireplaces.

If your oven is freestanding, you can pour a four inch slab on a well drained crushed rock bed. The gravel drains away standing water, and prevents frost heave.

Here's an interesting article from Canada, detailing a method of building shallow insulated footings. You need special high-compression insulation board to withstand the weight of the structure for this.

ESB: Frost-Protected Shallow Foundations

Good luck with your project.

[staestc]

Re: Foundation and a cold Canadian winter

Welcome to the forum Ekah!
Travis n'Texas

[dbhansen]

Re: Foundation and a cold Canadian winter

I live in northern Wisconsin and did a deep foundation. Not necessarily the best way to go, but it works. Pics are available via the 2 links below.

[sarah h]

Re: Foundation and a cold Canadian winter

Hi Ekah, and welcome!

I'm in Ottawa too and built last fall on just a 6 inch slab on top of a gravel bed.
If I had done more research first, I might have gone with something more substantial but my oven survived last winter without any problems. That said, however, please don't take this as a recommendation - I don't feel qualified enough to provide one - just saying what I did ...

Are you right in the city or in the outskirts?

Best of luck with whatever you decide to do - I'll look forward to watch your progress here on the forum.

Sarah

[Versachi]

Re: Foundation and a cold Canadian winter

Welcome Ekah. Another Canadian yippee! I'm up in Thunder Bay with winters much worse than most here on the forum. I dug down 16 inches and filled it with gravel which I compacted and have a six inch slab on it. No movement in the slab last year. Keep in mind that the ground where my slab is is very sandy so there is little water in soil which would cause it to move.

Cheers, Versachi

[ekah]

Re: Foundation and a cold Canadian winter

Thanks to everyone for their comments. Given that winter is just starting to be a reality, I won't undertake the construction until next spring. Until then, lots of planning to be done.

Thanks again.

[Ed_]

Re: Foundation and a cold Canadian winter

Here's an interesting article from Canada, detailing a method of building shallow insulated footings. You need special high-compression insulation board to withstand the weight of the structure for this.

The article is definitely worth a read. Although they do emphasize the need for sufficient compressive strength in the insulation beneath the slab, I don't think that's too big a concern for an oven.

A quick bit of math shows that if you have a 5' by 6' slab, the slab plus the structure on top of it would have to weigh over 21 tons to get up to 10 psi on the insulation. You should definitely check specifications, but I think most extruded polystyrene insulation is rated at 10-15 psi. And while your oven will be pretty heavy, you won't come close to 20 tons, so you have a good margin of safety.

For comparison, ten cubic yards of concrete would weigh about 20 tons.

[John.Halder]

Re: Foundation and a cold Canadian winter

I live in northern Wisconsin and did a deep foundation. Not necessarily the best way to go, but it works. Pics are available via the 2 links below.

Daren,

Thanks so much for such a comprehensive set of photo's. Wow. It's almost an instruction manual by itself.

I've been wondering for a while on the type of foundation - but I think if I followed your deep one I'd need to hire a back hoe - judging by the photo's I've got about 20 more years on me than you do, and I'm not sure I'm up to that amount of digging! Our climate will be about the same, though - I'm close to Iowa City.

Did you use the Forno Bravo plans?

Again - thanks for the "help."

John

[rroughtrade]

Re: Foundation and a cold Canadian winter

Here in Atlantic Canada, we have many of the same problems that you have in Thunder Bay, though our winters have a much shorter thaw and refreeze cycle meaning that we are a little more prone to frost heaves. Instead of building a poured slab foundation, we are thinking of going with a poured footing which will both keep the costs down and be resistant to frost heaves. At least in theory, this should protect us from both frost heaves and water inflitration if we get heavy rains.

[dbhansen]

Re: Foundation and a cold Canadian winter

Did you use the Forno Bravo plans?

Glad my pictures were useful, John! Yes, I did use the Forno Bravo plans, and borrowed ideas from lots of other members' pictures. Digging the foundation was a LOT of digging, but it went surprisingly quick given our thick clay soil. This is the foundation's first winter, so I'll see how she held up once the snow melts. If you have to dig by hand, I think the floating slab might be the best way to go.

Daren

[tdibratt]

Re: Foundation and a cold Canadian winter

I built mine in Canadian Winterland as well. I used the floating slab approach which I learned when I built a garage a few years back up in the Parry Sound area. The concrete slab is built with integrated footings about 12-16 inces wide and 12 inches deep. When I did the garage we did not even require insulation. The concept is to dig down your perimeter trench 12-16 wide and 12 inches deep so that the inside perimter of the trench is tapered. For example if I was looking at a cross section of the trench on the right side, the outside cut would be straight up and down. The inside cut would taper from say 16" wide at the top to 12 inches wide at the bottom. So the line would go from left to righ as you go from top to bottom. If you picture this effect all the way around you essentially create an area where when poured with conrete locks the slab into place so it cannot shift left to right. You then put in rebar into the trenches. 2 rows. Use vertical peices of rebar to hold the two rows in place and have them extend up high enough so that the actuall slab rebar grid ties into the vertical pieces. You create a rebar structure with the rebar in the footings and the slab tied together. Pour your concrete. Now if monther nature wants to play with your slab ans try to heave it a bit, the whole slab will raise and lower with frost but not impact the structure on the slab. That is the concept. Now what I did for my own is I went down far enough in the perimter to give me about 3-4inches od gravel, followed by 2 inches of blue syrofoam insulation (ridgid) and then the concrete went in over this. This has been my first winter and although I have not gone out to inspect closely, I can see my oven from my window and nothing appears to have moved. Again even if it did, the whole oven would move with the slab. I am no engineer so I cannot comment on this process being bullit proof but it worked for me and makes sense.