What is the definition of Substrate in a roofing system?

The definition of substrate in a roofing system refers to the insulation and/or the structure that forms the base layer upon which roofing materials are installed. This layer is crucial because it provides the necessary support and stability for the roofing components above it. The substrate helps to distribute weight, prevent sagging, and protects against moisture intrusion. It can consist of various materials such as plywood, oriented strand board (OSB), or concrete, depending on the type of roofing system in use.

The other options highlight different aspects of roofing systems but do not accurately define substrate. For instance, protective coatings, decorative finishes, and underlying supports for roof tiles are all important elements within a roofing system, yet they serve different functions and do not encompass the broader definition of what a substrate is in this context. Thus, the definition of substrate encompasses the critical role it plays as part of the overall roofing structure.