What is the purpose of installing a "drainage mat" in a BUR system?

Installing a "drainage mat" in a Built-Up Roofing (BUR) system primarily serves to facilitate water movement. The drainage mat is specifically designed to allow water that may accumulate on the surface of the roof to move efficiently towards the drainage points. This is vital as standing water can lead to a number of issues such as premature roofing material deterioration, leaks, or even structural damage due to the increased weight from the water pooling.

By promoting effective drainage, the mat ensures that water does not linger on the roof surface, thereby prolonging the life of the roofing system and maintaining its integrity. This feature is essential in preventing water-related problems that can significantly affect the performance and longevity of a BUR system.