In message , John
Rumm writes
On 26/04/2014 21:21, James Jones wrote:


I have some "stepping stones" set in to my lawn: 9x18 cms and also a
couple of paving slabs : 60x75 cms which have sunk.
Is it better to relay them on "blobs" of cement rather than just
trying to get a sand base nice and level. I am think if large blobs
of cement are used it will be easier to get them level by tapping them
down with a rubber mallet. (The paving slabs take no vehicles)

The dab and dot style of slab laying is always a bodge really - and the
results never really lasts well IME.

Assuming the base if well compacted and firm (if not get a some bags of
type 1 MoT, rake out a thin sub base screed of it, and then compact it
down well (plank and a lump/sledge hammer will do small areas)

Then I would say you will find it easier to just knock up a dry[1] mix
of weak sand and cement, and level them on that as if you were doing it
on a screed of sand. Water them once down and the moisture in the soil
and what you add will cure the mortar bed. The small amount of cement
binder will then keep it in place and stop it being migrated by
insects, or spreading out at the edges etc. It also means the slab is
fully supported and should not crack with a load on it.

[1] Use sharp or "grit" sand, and no more added water than what is in
the sand. Add cement at anything from 6:1 or even 10:1. That will be
adequate to act as a binder - you don't need massive point load
strength here.

As above except I find creating ridges in the sand/cement dry mix by
drawing the surface with a garden rake helps with slab levelling.


--
Tim Lamb