What is the effect of thermal expansion and contraction on BUR systems?

Thermal expansion and contraction play a critical role in the performance of Built-Up Roofing (BUR) systems. As temperatures fluctuate, the materials used in BUR systems—the bitumen, felts, and other elements—expand and contract accordingly. If these movements are not properly accommodated, they can lead to significant structural issues such as cracking or delamination of the roofing layers. Cracking occurs when the materials are unable to flex adequately, while delamination can result from the weakening of the bond between layers as they move apart. Therefore, it is essential for BUR systems to incorporate proper design features and materials that allow for movement due to thermal changes. This understanding is paramount for ensuring the longevity and integrity of the roofing system.