Roofing of gravel is only used on flat roofs. The gravel layer ensures that the layer of bitumen roofing is not drying out, so that the roof remains in good condition for a longer period of time. Flat roofs with a layer of gravel will be seen in plenty of places. Consider the extension of a house or a warehouse.
Roofing gravel can be used not just anywhere. The construction of the building must be calculated because of the heavy layer of gravel.