What does a "cap sheet" in BUR refer to?

In Built-Up Roofing (BUR) systems, a "cap sheet" is crucial as it serves as the final layer that protects the underlying materials. This layer is typically composed of granulated or smooth surfaces, which not only act as a barrier against environmental elements such as UV rays, rain, and wind but also provide additional durability and resistance to wear and tear.

The cap sheet effectively enhances the waterproofing of the entire roofing system, helping to prevent leaks and prolonging the lifespan of the roof. It's an essential component for ensuring that the materials beneath it remain intact and sheltered from potential damage. Understanding the role of the cap sheet is instrumental in grasping how BUR systems function effectively, ensuring both protection and longevity.

Other options do not accurately describe the cap sheet's function, as they focus on insulation, the position of the layer in the installation sequence, or aesthetics, which are not the primary roles of the cap sheet in a BUR system.