An inverted roof system is a type of flat roof construction in which the insulation is placed on top of the waterproofing layer. This is the opposite of a conventional flat roof system, where the waterproofing layer is placed over the insulation. In an inverted roof system, the insulating layer helps protect the waterproofing layer from damage caused by weather and UV rays, while providing thermal insulation and reducing heat loss. The insulating layer can be made of various materials, including rigid foam boards or mineral wool, and is usually covered with a layer of gravel or pavers to protect it from damage and provide a stable surface for maintenance workers . The waterproofing layer is generally made of bituminous membranes or synthetic materials such as PVC or TPO.