How do built-up roofing and modified bitumen mainly differ?

Built-up roofing (BUR) and modified bitumen roofing primarily differ in their construction methods and the materials utilized. Built-up roofing is created by layering felts or fabric saturated with asphalt and can include a surface layer that provides protection from UV rays and weather. The layering process is fundamental to BUR, which typically involves multiple plies to create a durable and waterproof surface.

On the other hand, modified bitumen roofing combines traditional asphalt with polymerized modifiers that enhance its elasticity and performance. This roofing type is often installed in a single-ply membrane format and can be applied through methods that involve heat (torch-down), adhesives, or cold adhesives. The use of these modifiers and the application processes distinguish modified bitumen from traditional BUR.

While there are variations in color options, weight and thickness, those factors are secondary attributes rather than core differentiating principles when considering how these two roofing systems are structured and designed. Thus, understanding the construction methods and materials is crucial for distinguishing between built-up roofing and modified bitumen.