On Wed, 30 Apr 2014 15:10:22 +0100, John Rumm
wrote:


So greenhouse bases put solely on a slab sand base - especially in a
very wet area - will be fairly wobbly after about how long?

They may never get wobbly - although the levels will usually shift.
Often there will be no trace of the sand if you lift a slab later.

Frequently wet areas are worse - but the effect will vary with soil
conditions.

The plot I am thinking of has slabs covered with water when it rains
a lot.

https://www.flickr.com/photos/25345470@N02/13694025513/

https://www.flickr.com/photos/253454...n/photostream/
The greenhouse at the end ..
It is the second wettest plot. Up from the wettest one which is
diagonally left in the second picture.


If the slabs are above ground level (rather than on it "in" it) then the
edge ones usually tip outward as the sand escapes from the edge.

What about postcreting posts in for the corners for my greenhouse
base, someone's suggested pressure treated boards around the bottom to
make like a raised bed to sit it on.

What kind of soil do you have?


Soily with masses of clay underneath the wet plot. He tried digging
through it but gave up.

Mine is much more loamy on the bit I want to put my greenhouse on and
it's a bed I've dug and cultivated so it's a bit soft. Lovely for
growing in though.
Would I be better finding a different bit for the greenhouse? The
whole plot gets the sun and there's no issue of shading another plot
on most of it.

For slabs used as a shed or greenhouse base, adding enough cement to the
sand to let it set a little once laid is usually all that's needed to
keep it in place. (used as a dry mix - no need to actually turn it into
mortar prior to laying)

'k. Ta. I think they have just used sand from the bag - not seen
cement bags anywhere.
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