ᐅ The strip foundation has developed a crack.

Created on: 9 Nov 2021 11:51
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Peug408
Hello, greetings from Russia.

I am building my house here. Temperatures reach up to +45°C (113°F) in summer and down to -20°C (-4°F) in winter. Two years ago, I poured the foundation with 18 mm (0.7 inch) reinforcing steel inside.

Groundwater appears already at 50 cm (20 inches) depth, so I raised the foundation. It is 50 cm (20 inches) deep and 50 cm (20 inches) high.

Now I have noticed a crack that was not there last year. I am not exactly sure of the cause, but first, I had 200 cubic meters of soil delivered and raised the plot. I suspect the groundwater at depth froze.

The crack runs from the top down to about half the height of the foundation, as if it was pushed up from below.

My question is, how dangerous or problematic could this crack become? I am considering pouring a 15 cm (6 inch) high slab completely over it, including on the foundation.
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Peug408
5 Dec 2021 19:55
Ah, that’s what it means—the floor areas should not be filled with topsoil.

How many centimeters (inches) should be removed?
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guckuck2
5 Dec 2021 21:10
Everything. How are we supposed to know how thick this layer is :-)
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ypg
5 Dec 2021 21:48
Everything! And also outside the strips. At least 100cm (40 inches), preferably 150cm (60 inches). Foundations should NOT have any contact with soil or topsoil.
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Peug408
18 Dec 2021 06:48
So, I’m checking in again. I have replaced the layer with gravel, about 100cm (40 inches), and I’m planning to pour concrete soon.

However, I’m concerned about the temperatures. During the day, it can reach up to 10°C (50°F), but at night it drops to around -3°C (27°F).

I spoke with the company supplying the concrete, and they said it’s not a problem at all since they also operate in northern Russia where they pour concrete in temperatures as low as -20°C (-4°F).

They mentioned that a frost protection additive is used, but how reliable is that?

What would you suggest? Should I go ahead with the concrete pour or wait for warmer weather?
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guckuck2
18 Dec 2021 08:34
With the right mix, it works. To use the "Russia" argument: in other places, the weather is often colder, and it still works there – with the proper mix.

Your biggest risk is going it alone, not following professional advice.
Tolentino18 Dec 2021 09:23
I don’t know about -20, but for me it was down to -5 and no problem.