This is perhaps the most critical spec. The "Class" number indicates the joint movement capability expressed as a percentage of the joint width.
Sealants are critical components in a building's envelope, tasked with preventing air and water infiltration while accommodating movement between different building materials. ASTM C920 ensures that a product has undergone rigorous testing for specific characteristics, such as: astm c920
A report on ASTM C920 typically classifies a sealant based on the following criteria defined by ASTM International: : This is perhaps the most critical spec