Problems caused by varying degrees of moisture content in wood go beyond simple shrinkage including distortions in the shape of the wood, such as twisting, warping and cupping. In cupping, timber floor boards roll up at the edges to form ridges with dishing in the middle of each board. As the moisture content increases the boards expand and push against each other forcing the cupping to occure.

 Floor Cupping Picture   Floor Cupping 2 Picture