What typically causes considerable wrinkling and tauntness of EPDM and PVC membranes at wall intersections?

The correct choice is that shrinkage of the membrane typically causes considerable wrinkling and tautness of EPDM and PVC membranes at wall intersections.

When these types of roofing membranes are installed, they are usually laid out flat and securely fastened to the underlying structure. However, over time and due to various environmental factors, the materials can shrink. This shrinkage occurs because EPDM and PVC are thermoplastic materials that can contract when temperatures drop or as they age. The tension created by this shrinkage pulls the membrane tighter at wall intersections, leading to wrinkles and a taut appearance.

These wrinkles can compromise the integrity of the roofing system, potentially leading to leaks or other performance issues. Proper installation techniques can mitigate such problems, but they do not eliminate the natural shrinking process of the membranes over time. Understanding this process is essential for assessing roof performance and planning for maintenance or replacement.