What is the key characteristic of "bituminous" material relevant to BUR?

The key characteristic of "bituminous" material relevant to Built-Up Roofing (BUR) is that it has a sticky, black substance used for waterproofing. Bituminous materials are primarily derived from the distillation of crude oil and are characterized by their sticky and viscous nature. This quality is essential in roofing applications, as it provides excellent waterproofing properties, ensuring that the roof remains resistant to moisture intrusion.

In BUR systems, bituminous materials are typically used in layers, acting as both an adhesive and a protective barrier against the elements, particularly in flat roof designs where proper drainage is vital. This characteristic makes bituminous materials particularly effective in creating a durable and long-lasting roofing solution.