Sleepers&Garden Bed

Zahid_63c

I have two queries:
1.I plan to put in 2 sleepers which are both 20cm high 
How deep do they need to he put into ground in order to stay sturdy and upright? 
If I put posts in at back would that mean they don't need to go in as deep 
I would like them as high as possible 
2.I plan to have topsoil and then slate as mulch in the garden border
If for example the sleepers were 30cm high 
How many centimres topsoil and then slate would I ideally put and how much do I leave empty at the top?

Fairygirl

Hi @Zahid_63c - sleepers are quite hefty, so if you're only having them at that height, they should be fine just stacked. If it's a long border you're doing, as opposed to just one length of sleeper, you'd be better having some supports. Many people drive steel rods down through them, into the ground below, which works well. But you could put in a few fence posts, concreted in, if that's easier. 
For filling it - you'd fill it up right to the top, and your slate would end just an inch or so from the top of the sleepers. 

Zahid_63c

Thanks
When you mean long border do you mean higher?
The border is 5m so yes there will be a few lined up