Built-up roofing systems (BUR) consists of layers or plies of roofing felts, between which asphalt or bitumen is applied. Built-up roofing is one of the oldest and most durable systems available. Its multiple layers provide extra protection and perform well in extreme weather conditions. Built-up roofs are especially resistant to damage from wind, hail and snow. They are easy to repair and ideally suited for applications requiring a high level of redundancy.