What roofing technique utilizes seven layers for construction?

The roofing technique that utilizes seven layers for construction is built-up roofing (B.U.R.). This method involves alternating layers of roofing felt and bitumen, which are applied in multiple layers to create a durable and effective waterproof barrier. The traditional B.U.R. consists of a minimum of three layers of roofing felt, but when properly constructed with additional layers, it can reach up to seven layers or more. This multi-layer approach provides excellent weather resistance, insulation, and a long-lasting surface. It is particularly effective for flat or low-slope roofs, making it a popular choice in commercial applications.

Single-ply roofing techniques generally use a single layer of membrane rather than multiple layers. Metal roofing involves sheets of metal, usually with a much simpler installation process. Tile roofing consists of individual tiles that are placed in overlapping patterns, which also do not involve multiple layers like built-up roofing does. Understanding the distinct characteristics of each roofing type highlights why built-up roofing stands out for its layered construction technique.