Foundation - How deep must the hole be at minimum?

Hello everyone,

I urgently need expert help because I am quite inexperienced in this matter.

To the point:

I would like to make a 2mx2m foundation on my property. First of all, I want to say that I live in the African wilderness and the soil consists only of sand. You can easily dig one meter deep without hitting a single stone. However, the soil becomes quite compact at a depth of 30 cm (so not like on a dune). I need a solid ground on which I can move without sinking :p. Apart from my own weight, the foundation does not need to bear any load.

I have gravel, cement, and sand. But above all, I have no idea how to do something like this.

Here are already some questions I have (for you):

How deep do I need to excavate this area?
Should gravel be put into this hole first to stabilize the ground?
What should the mixing ratio of gravel/cement be to make it stable?
How long does it take for something like this to harden (as info: temperature during the day = 40°C +)?

I hope these questions are not too silly. But as I said, I have zero clue!

I am grateful for any tips. Probably there are also points I have not considered.

Thanks in advance for your help

Best regards
Paulus

Hello Paulus,

if you mix the concrete yourself, use gravel with a grain size of 0/16 and Portland cement PZ 35 in a mixing ratio of 4 parts gravel and 1 part cement. Of course, water is also needed. The ratio of water to cement (measured in grams) should be about one to two. For example, with 10 kg of cement, this corresponds to 5 kg or 5 liters of water.

Hello Paulus,

if you mix the concrete yourself, use gravel with a grain size of 0/16 and Portland cement PZ 35 in a mixing ratio of 4 parts gravel and 1 part cement. Of course, water is also needed. The ratio of water to cement (measured in grams) should be about one to two. For example, with 10 kg of cement, this corresponds to 5 kg or 5 liters of water.

Hello 6Richtige,

Thank you for the prompt reply! The mixing ratio is now clear (yes, I have water too :D ).

Do you (or anyone else) perhaps also have a tip or comment regarding the other points?

Curing: Approximately 1 week, do not forget to water so that the slab does not develop cracks.

Depth: The base should be made of material that allows water to drain, gravel or similar, well compacted. The slab should be about 10 - 20 cm thick, depending on the intended use. It probably does not need to be frost-free ;) Steel reinforcements to prevent cracking also do no harm.

:) Thank you 6Richtige,

that would settle everything.

And here we go...