On 30/04/2014 13:14, David Hill wrote:
On 30/04/2014 10:54, mogga wrote:
On Sun, 27 Apr 2014 14:28:03 +0100, John Rumm
wrote:

So far so good....

and top off with sand.
Don't use any cement, there's no point, it's just a bodge method.

Could I suggest you go read some of the British standards on paving
techniques? To describe using a bound bedding layer (i.e. one containing
cement or lime) as a "bodge" is inaccurate and misleading.

Generally, "sand only" screeds tend to be used for smaller element
paving such as blocks and sets, and screeds with a binder used for
larger slabs - however this is not a hard and fast rule.

However the critical requirement of any sand only screed is that the
edge is adequately retained - typically with a mortared in place bedded
on course of blocks or edging stones, but sometimes just a concrete
haunch. Without the edge restraint, the sand will migrate out, and will
also get migrated by insects. and worms etc.

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

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.







For chapter and verse on bedding courses, have a look at:

http://www.pavingexpert.com/layflag3.htm#bornb

For general on flags:

http://www.pavingexpert.com/layflag1.htm

For Gods sake read the OP.

Did you spot the "which have sunk" bit?

Assuming that was the problem he wanted to fix...

(note also the discussion has moved onto greenhouse bases)

"I have some "stepping stones" set in to my lawn: 9x18 cms and also a
couple of paving slabs : 60x75 cms which have sunk."

He's not laying a patio or even a path.

So?

If you want to be able to level them and not have them sink again, do
what has been suggested...

Lift the stone. Unless the soil is rock hard and stays that way all
year, chuck in a thin layer of type 1 and ram it down so you have a good
sub base to work from. Now rather than re-bedding the stone on just
sharp sand, add a small amount of cement to it. Its only going to take 5
minutes to do it properly. That will stop the worms etc from romping off
into the lawn with your bedding, or having it flushed out with too much
water.

--
Cheers,

John.

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