Do I really need that much concrete ???

30 Aug 2011
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United Kingdom
Hi all. I'm new to the forum. I just have a quick query before buying some concrete.

I am putting up a green house and have dug some footings for a concrete base. The base will just be a ring of concrete, not the whole floor. The foundation trench is a total of 12.6m around all four sides of the green house by 0.30 m wide by 0.25 m deep except the front which will be 0.60m wide by 0.25m deep

The greenhouse is 8' x 6'.( 2.44m x 1.8m)

i envisage putting 0.15 m thick layer of hardcore in the bottom of the trench then filling the rest up with concrete. 0.10 m thick

I calculated the concrete required to be 38 cubic meters and weighing in at about 2.3 tons :eek: . This seems like a lot of concrete.
I'm just after a sanity check really to make sure this is around the right figure.

If this figure is about right, is it feasible to mix this by hand in a wheelbarrow and lay it in one day ?


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Urm i make it somewhere between 1.5 and 2cu ish.. so your a little off..

2.44x0.25x0.6 = urm around the 0.4cu mark
10.2x0.25x0.3 = 0.8 ish
2.44x1.8x0.1 = 0.4 or there abouts..

Anyways.. im going to keep looking for my calculator now..
Where do you get those figures from Static?

2.44x0.3x0.1 = 0.08 X2 = 0.16 (sides)
1.8x0.3x0.1 = 0.054 (back)
1.8x0.6x0.1 = 0.11 (front)

So total required = 0.25m3

The size of your foundation is not very clear tbh
I think it could actually be less because the wide part of the trench is on one of the shorter sides so it could be :-

Trench depth = 0.25 of which 0.15 is hardcore leaving 0.1 concrete and so .....

length x width x depth of concrete = Cubic m of concrete
2.44 x 0.30 x 0.10 = 0.07 ish
2.44 x 0.30 x 0.10 = 0.07 ish
1.80 x 0.30 x 0.10 = 0.055 ish
1.80 x 0.60 x 0.10 = 0.10 ish

Totaling 0.30 ish m Cubed

That sounds a bit more reasonable. Previously I used an online calculator and must have gone a bit astray somewhere....

Does this sound a bit more sensible ?
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Sorry Freddy. Was posting my reply as you posted yours. They seem to tally quite well though. :D

Thanks guys. Could have been difficult trying to sell a LOT of second hand concrete. Quite a tough market to crack :oops:
13m x 300mm wide x 300mm deep would require 1.17m³ of concrete which would equate to about 2 tonne of ballast and 14 x 25kg's of dust.

So, why don't you but a tonne sack of ballast and 7 bags of dust then see how much more you need.

A join in a greenhouse footing aint gonna hurt none.
...Just to add to my original post:

Don't bother with hard core in the trench bottom just use concrete hence the thicker or deeper concrete.
Sorry miss read the bit about putting in hardcore under the footing and read it as a slab over lot..
Do as noseall says all concrete

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