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

The considerable wrinkling and tautness of EPDM (Ethylene Propylene Diene Monomer) and PVC (Polyvinyl Chloride) roof membranes at wall intersections is primarily caused by shrinkage of the membrane. Over time, these synthetic materials can experience changes due to temperature fluctuations, UV exposure, and age. When a membrane shrinks, it can pull away from the substrate or wall, leading to visible wrinkles and tension at the points where it intersects with walls. This phenomenon can compromise the roofing system's integrity, potentially resulting in leaks or further damage.

In contrast, factors like improper base flashing details, poor securement of fascia, or lack of proper counterflashing may contribute to other roofing issues but do not specifically lead to the wrinkling and tautness observed at wall intersections as directly as shrinkage does. Understanding the materials' properties and reactions to environmental conditions helps in identifying the primary causes of these roofing issues.