Concrete base

[simonzebu]

Hi, I am putting up a large 5x3 metre shed. Can anyone tell me how thick the concrete base should be?
I figure laying and compacting hardcore first, how deep should that be?
Should I be putting some sort of membrane into the equation?
cheers Simon B

 

[Richardp]

The slab above ground should really be 6 inches thick and a damp proof membrane under it. For small sheds this could be dug into the ground 300mm wider and longer than your shed , 4inches deep and pour the concrete onto the damp proof membrane. make sure the ground is level over the area of the base.
I personally think 4 inches is plenty what ever.

 

[JohnD]

?but if the slab is dug in, and the membrane is below it, surely ground water will soak in from the sides?

I had envisaged a sort of "tray" with the membrane turned up at the edges - or possible edges treated with Aquaprufe sort of thing.

Difficult to make a join unless there is a little wall or strip used as formwork.

How do other people do it?

 

[Static]

Its just a shed.. 150mm thick (6") base about 20mm above ground level, DPM below then sand blinded hardcore (150mm thick)...

Or as it is just a shed make a paving slab patio base and then you may have to re-bed some of the slabs every 5-6 years but will be alot cheaper