On Sun, 27 Apr 2014 14:28:03 +0100, John Rumm wrote:

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.

The slabs in my garden were layed by my brother in about 1980; if there was
any sand, it's long since disappeared. The slabs are still firm and dead
level. This is almost certainly due to the soil being somewhat heavy and it
hadn't been disturbed at all since at least WW2!

On the other hand, in a friend's garden that had a high water table, light
soil and loadsamuck, some of the (fortunately 2x3) slabs were only about 25%
supported by anything - they definitely needed sand and binder and probably
some hardcore as well.
--
Peter.
The gods will stay away
whilst religions hold sway