Type of roof in which thermal insulation is placed above the waterproofing material. This insulation consists of impermeable materials in the shape of stiff foam panels of extruded polystyrene and is covered with a protective layer or practicable coating. The inverted roof is a practical system both from a technical viewpoint and regarding the physical construction.

Roofing support and waterproofing are protected from thermal actions and UV rays by insulating material and ballast. The ballast must be able to prevent the insulating material from being detached or lifted by the wind.