Although wood flooring has been dried, cut and treated, it is still a natural material, so it will continue to respond to humidity levels during the changing seasons. This means during the warmer seasons it will expand as it soaks up moisture and during the colder times, it releases that moisture. When the wood releases that moisture, it will contract forming thin gaps between the planks. This should not be a major cause of concern, just something a wood floor home owner should be aware of.
There are four main reactions a wood floor will have due to changing moisture levels:
Cupping: Cupping occurs when there is too much moisture causing the planks to expand and squish together. This forces the edges of the planks upwards so that they are higher than the center. Cupping can usually be reversed by drying out the wood naturally or by placing some fans in the room to speed up the process. Also, a dehumidifier can help maintain a healthy moisture amount in your home.
Crowning: Crowing is the opposite of cupping. It is when the center of the planks is higher than the edges. It occurs most often because of sanding down the floors while they are cupping. Once the room reaches normal moisture levels again, the wood will contract revealing the overly sanded edges.
Buckling: Buckling is the rarest and most extreme reaction a hardwood floor will have to moisture. It is when the floor pulls up and away from the subfloor. This usually only occurs after the floor has been in contact with a large amount of moisture like after flooding. Luckily, the floor can usually be repaired instead of having to be completely replaced.
Gapping: Gapping most often happens during the end of fall and winter when moisture levels decrease. It is when the planks contract due to the loss in moisture and recede from one another, creating thin gaps between the individual planks. The problem can be fixed fairly easily by adding a humidifier to establish normal moisture levels.
Again, these reactions to moisture can be controlled by monitoring the moisture levels in a home. Adding a humidifier during dry winter months will help control or lessen gapping just as adding a dehumidifier will help the natural hardwood reactions during warmer seasons.
