Low wall - straight onto soil?

Hi!

I have sufficient old crazy paving slabs (ex council) to build a low wall, no more than 4 slabs high. This will act as the front of a rose bed and whilst it will do a limited amount of soil retaining, I am confident it won't need mortar.

Question is, if I level the soil and compact it, will that be suitable to lay the slabs directly down or is it highly recommended to put a layer of sand etc down first?

Thanks in advance.

B 

If you are building a wall 4 slabs high i would lay a compacted layer base of ballast or some cast concrete and cement the slabs down.

If you just lay the slabs down onto the soil the soil may sink with the weight of the slabs above it and the wall will deform , and with the weight of soil ( especially if the soil is wet) behind the wall ( even though it is quite small) might still be enough to make the wall bow or collapse over time.

might seem a bit excessive for a wall 4 slabs high but better safe than sorry !

Thanks Allymc ... good point (it would be a pain having to redo it). If I use compacted ballast, are you suggesting I concrete the slabs onto that or will the ballast be sufficient?

Thanks again,

B