Soon after installation, movement from expansion, contraction and other forces placed normal stresses on the sealant bead. The sealant would pull at the primer it was bonded to and cause it to release from the primed natural wood substrate. The primer’s adhesion to the wood’s surface was failing, but the sealant’s adhesion to the primer was performing as intended. To understand this observation better, the issue required further examination. The process that began on the jobsite was later replicated and studied in greater detail back home at OSI’s application center just outside of Cleveland, OH. The results are outlined below and brought to life in this short 3-minute video.
Consumers and installers alike will choose natural wood, cladding and siding products for a number of different reasons including aesthetics, price and workability. However, natural wood products, especially those of various pine species, are less stable when compared to engineered products. They are more susceptible to deformation, expansion and contraction resulting from moisture and temperature fluctuations. These variables, if not managed properly, can lead to primer and paint bonding performance problems with the substrate’s surface itself. This was observed and studied by OSI® building science expert, Paul Majka, primarily in regions of the Northwest and Northcentral United States.