Cupping and crowning are caused when water is trapped between the wood floor and the subfloor. Cuppping occurs when the floor is caused by changes in moisture levels in the air, due to excessive moisture which causes the wood flooring to swell. When the boards crush together and deform at the edges, it forms a “cup” due to the excessive moisture. Crowning is the opposite, when the center of the board is higher than its edges. Crowning can occur when the surface of the floor encounters moisture or is left in wet or humid conditions for an extended period of time. 
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