Tags: #buildingdesign #buildingmaterials #buildingproducts #buildingscience #facecolumn #materialsscience #water

Water moves in mysterious ways: the role of surface checking and wood grain in water migration through plywood. 

Face checking is the bane of plywood’s existence. It significantly influences the rate of water migration into a given ply, between plys, and through the greater laminated panel. 

Water begins to move between the plys almost instantaneously and is released within seconds at the bottom edge of the test panel. By the first minute, we see water weeping from the exposed cracks. At approximately two minutes, notable release has occurred at the sides of the apparatus – 8 inches from the column edge! And finally, at five minutes, water is released on the back side of the panel.

I also show how water traverses a tape interface in response to hydrostatic pressure. In this case, I’ve simply placed a three-inch wide strip of tape just above the column. Water flows upwards along the wood grain through exposed wood fibers. Interestingly, water migration is a function of fiber morphology. Notable capillary flow is seen in the wider, lighter fibers; and less flow is seen with the narrower, darker fibers.