Posted: 26/03/2016 at 16:57
Hedge plants will need a loam-based growing medium and a lot of it, which in it's turn will hold a lot of moisture. The weight will be considerable. What weight will your roof terrace take?
How high up and how windy is the roof terrace? I think that many conventional hedge plants will struggle in an exposed windy site. They will also need a great deal of watering.
Have you considered using bamboo or other tall grasses as a screen rather than conventional hedge plants?