Concrete base for shed

[diydavellis]

I am putting up a wooden summerhose with a base area of 4.2 sq metres.
I think that a 50 mm thickness will be enough.
If so, how many bags of prepacked concrete should I buy (25Kg bags)?
diydavellis

 

[Scoby_Beasley]

8.4
Okay say 10.
Or maybe 84 !
Lengthxwidthx depth in cm = cubic centimetres
25kg = 25000 cc
Divide top by bottom (ooh err matron !!)

 

[TexMex]

Length x Width=4.2
Depth=0.05m
Volume therefore=0.21 Cubic Metres

Dry concrete mix is approx 1.7 tonne per cubic Metre (heavier than water!)

.021 x 1.7=0.357 (357 Kg) = about 15 bags.

 

[masona]

If so, how many bags of prepacked concrete should I buy (25Kg bags)?

It will be cheaper to have it deliver than buying bags and you don't have to put it in your car !