There are many more factors to take into account when designing a roof garden or terrace. The most important one being what load can the existing roof take and access for materials.
This is an interesting product that allows for decking to be installed quickly and lifting it off the existing roof space to allow for drainage, cables etc. This product is also available for the installation of stone / concrete tiles.
For more info decking roof supports
Once again, load (weight) is an extremely important factor when embarking on a roof garden design, a structural engineer should always be consulted.
