[peterjames]

The immediate benefits of having a flat roof system are its cost efficient use of available space. With a traditional roof, the angular slope means a great deal of unusable space goes between the ceiling and the surface of the roof. This is what we typically call the attic. On a flat roof you make the maximum use of space below the roof. Also because the roof is flat, you can use the space on top of the roof as well. Recreational roof gardens and other such things are common uses for the newfound space. It also makes the installation of solar panels much easier.