With city living on the increase, roof gardens are literally on the up. However, they bring with them their own problems.Wind can blow over pots, make a mockery of water features, and dry out and kill plants in weeks.
You can filter or slow down the wind using a trellis or screening that allows the wind to blow through. Solid structures, on the other hand, can be)damaged by strong wind, and they also create eddy currents where the wind simply flows over them.
Plants need to be drought-resistant – ideally, choose species that grow well in coastal regions, because they’re used to similar conditions. Deciduous shrubs and perennials that die down in autumn will also avoid the worst of the weather in winter.
There is often no escape from the sun in a roof garden, so silver-leaved Mediterranean plants such as sant-tolina do well. If you can afford it, a simple automatic irrigation system is advisable.
Weight is always prohibitive, so if you’re thinking of converting, it is vital to have the roof inspected by a structural engineer. Use your common sense – any serious weight should be distributed around the edge, close to load-bearing walls.

Andy Sturgeon
The Guardian Weekend
March 24th 2007