A deck refers to the substrate or base layer of a roof onto which the roofing materials are installed. The deck is typically made of wood or a type of structural panel, such as plywood or oriented strand board (OSB), and serves as the foundation for the roof.
The deck is an essential component of the roof and must be structurally sound and able to support the weight of the roofing materials, as well as any snow, ice, or other loads that may accumulate on the roof. The type of deck used can vary depending on the design of the roof, the climate in which the building is located, and other factors.
Once the deck is in place, it is typically covered with an underlayment, which provides an additional layer of protection between the deck and the roofing materials. The roofing materials are then installed on top of the underlayment to complete the roof.