What type of roof consists of several layers of felt with hot asphalt applied and a gravel topping?

The type of roof that consists of several layers of felt with hot asphalt applied and a gravel topping is known as Built-Up Roofing (BUR). This roofing system is characterized by its multiple layers, which typically include alternating layers of felt and asphalt. The use of hot asphalt between these layers creates a durable, waterproof surface. The addition of a gravel topping not only serves as a ballast to protect the underlying materials from UV radiation and physical damage but also helps to enhance the overall longevity of the roof.

BUR is often employed in low-slope or flat roofing applications due to its robustness and ability to withstand various weather conditions, making it a favored choice in both commercial and residential settings. The other roofing types mentioned, such as metal roofs, single-ply membranes, and tile roofs, have entirely different construction methods and materials, which further distinguishes BUR as the correct choice in this context.