Posted: 28/10/2013 at 17:38
Only problem with sleepers is the creosote a lot of the old ones were painted with - it's very poisonous.
If you put your beds on top of the membrane plants will still grow well with a foot deep of soil.
However it's a lot of soil/compost to fill them. 1m x 3m x 0.3m = 900 litres of soil each and you want 3 = 2700 litres.