Adhesive Characterization & Durability of Self-Adhered Flashings

Self-adhered flashing products can very effectively maintain a durable moisture-tight seal at the window-wall interface, which is highly vulnerable to moisture intrusion. However, it is essential that these products be installed under conditions where adequate adhesion to the substrate is achieved. Also, the self-adhered flashing products must have thermal durability and dimensional stability to maintain their performance at the high temperatures that can exist behind siding. This study gives a preliminary adhesion characterization assessment of six self-adhered flashing products, three with modified-asphalt based adhesives and three with butyl based adhesives, onto several common building substrates and installed at a range of temperatures, including moist and dusty conditions. What is found is that the butyl based adhesive systems have a broader window of installation surface conditions and temperatures where “adequate adhesion” is achieved without the use of a primer than the modified-asphalt based adhesive products. Also, a thermal aging study shows that the butyl based adhesive products are more thermally stable than the modified-asphalt based products at typical temperatures behind siding. Also, film topsheets are more prone to deformation and curling after thermal aging than nonwovens composite or foil laminate based topsheets.