The strip foundation has developed a crack

Hi,

The foundation slab is now curing, so far so good.

Now, regarding the topsoil, I only replaced the topsoil with gravel in the areas.

Does this really need to be done along the strip foundation as well?
What are the advantages of this, or better yet, what are the disadvantages if the soil touches the concrete?

There is also a membrane in between, or there was one, as it is torn in some places.

80 cm foundation depth for your footing is definitely too little. In Russia, especially with the frosts. It must be founded frost-free, and I would see 2.00 m as realistic. Here in Saxony-Anhalt, we have already had frost down to 1.20 m.

I would say that is a settlement crack. Frost damage. Building on that will be difficult.

It might work, but it can also shift. Then the walls and the slab of your house will crack.

I built my terrace with a similar construction. I went 1 m deep with the strip foundation.

So in the south of Russia it is not so cold now, it can happen that it gets -20°C but that is rare. Currently we have up to +15°C again. Last week was colder. Dug was 90cm - 100cm, the excavator driver was not that precise. The foundation itself has the correct height 100cm, the problem was apparently that 50cm of it were only underground. The other 50cm were sticking out upwards. The rest is a gravel layer at least 40cm and that also pushes the groundwater away. But I think since I raised the ground around the foundation by 50cm, nothing should freeze anymore. At least I hope so.