How does rooftop gardening work?
Rooftop gardening or green roofs are fairly simple constructions and work on roofs with less than 20–30 degrees of slope. They all consist of at least these basic elements: a waterproofing membrane, a layer of soil, and the vegetation of choice. Green roofs can be built on roofs of old buildings too, as long as these can carry the extra weight. Once the garden is installed, it can be farmed by the inhabitants – should it include edible plants – otherwise it can be enjoyed as an additional green space within the city.