The layers that make up a built-up roof are called what?

The layers that make up a built-up roof are referred to as "plys." In roofing terminology, "ply" denotes a single layer within a multi-layer system, particularly relevant for built-up roofs (BURs), which consist of multiple layers of bitumen and reinforcing fabrics. Each ply is crucial for providing the roof with additional strength, durability, and waterproofing properties.

These layers work together to create a robust and weather-resistant roofing system. Understanding the term "ply" is essential for roof installation and maintenance professionals, as it directly relates to the construction and performance characteristics of built-up roofs. This knowledge helps ensure proper application techniques and effective repairs, which are vital for extending the lifespan of the roofing system.