The purpose of a sealant, or caulk, on the exterior of a home is to seal gaps that allow air and moisture to infiltrate the structure of the home. That seems simple enough, but the reality of building materials is that they are constantly moving. Changes in temperature and humidity cause them to continually expand and contract which means the size of those gaps is constantly changing. This means that the caulk filling those gaps is regularly being stretched and squeezed, so if it dries hard it will crack within a season or two due to the movement. To have…