We have an uncemented indoor area of about 20 m²/215 ft².

The underground is a layer of compacted gravel.

There will be no heavy loads or traffic, just storage space.

How much sand and concrete (cement?) do I need for this size?

I want to avoid the same mistake, that our Thai neighbour made:

After finishing his project he found out, that he bought the double amount of what was needed....

thanks

Here's a website that will help you figure it all out from your dimensions.
http://source4me.co.uk/calculate_concrete_mix.php

I always figure 4-5" for a garage, and 2-3 for just a warehouse with no car or truck needing to drive over it.

Good luck.

thanks, that helps a lot.

With 5 cm thickness I need matrial for ~ 1qm³ = ~350 kg cement + ~1qm³ sand/gravel (a little bit more just to be safe)

If you have established you need 7 bags of cement at 50kg ( and i agree) then you need to buy 1ton of sharp sand and 2ton of small gravel 10-30mm.

This will give you a general c20 mix in ratio 1:2:4 cement sand gravel.

This is a strong mix and you could thin it down to 1:3:6 which is even better and cheaper a bit less cement.

As a rule the weight of most material are 1.5x the volume; connie is 2x

So 1m3 is 2ton if you ever need to know the loadings.

1m3 is not worth getting delivered so i would start with 4 bags cem and the equivalent of 12 bags sand and 24 bags gravel if you want to see where that goes.

Here's a website that will help you figure it all out from your dimensions.

http://source4me.co.uk/calculate_concrete_mix.php

I always figure 4-5" for a garage, and 2-3 for just a warehouse with no car or truck needing to drive over it.

Good luck.

What a handy tool that is! It even tells you the number of litres of water to use. Thank you fiddlehead.

1m3 is not worth getting delivered so i would start with 4 bags cem and the equivalent of 12 bags sand and 24 bags gravel if you want to see where that goes.

Sounds like a very good idea.

Thanks