Wood flooring responds to humidity variations. During warm and humid months wood expands. In the colder months, dry conditions force the wood to contract. This seasonal movement is normal for wood flooring, and the best way to reduce movement is by installing humidity controls.

Winter time

In the winter months homes are heated and the air is dry, wood flooring then starts losing its moisture. When this happens, thin gaps can appear between planks. This is normal, and you should be prepared for it to occur. Once indoor heating is turned off humidity levels will raise again, most of the gaps will close up.

To avoid these separations, try to control and monitor air humidity levels during the dry season by installing a humidifier. You can either install a furnace humidifier or bring a movable humidifier into a room that has good air circulation. Optimal humidity level falls in between 45%-60% range. As long as humidity does not fall lower than 45%, no gaps will appear.

Summer time

During warm and humid months, indoor humidity can rise up to 90%. Wood absorbs moisture from the air and expands as a result. Even just a few days of exposure to high humidity can cause wood flooring to cup. When a wood board cups, the edges are at a higher level than its center. Cupping can also happen when spilled water is absorbed by the wood. Once cupping has occurred, it takes a while for the wood to restore its internal moisture and flatten out.

When extensive moisture or humidity causes the wood to expand significantly, adjoining boards start pressing against each other. In extreme cases, this increased pressure can cause the affected boards to lose their structural integrity and crack. To avoid cupping, keep indoor humidity level in your home or job site (prior to hardwood installation) within 45-60% range. Never allow indoor humidity to rise over 65%. Maintain optimal humidity levels by keeping air conditioner or dehumidifier running during hot humid summer weather.

Moisture and Exotic Wood Species

Flooring manufactured from exotic wood species is more demanding than flooring made from domestic woods. For this reason, a set of additional requirements has to be met when installing and maintaining an exotic hardwood floor. Indoor air humidity level must be in the range of 50-70%, and air temperature must be kept in the range of 64 to 75 F.

In order to meet these requirements, use an air humidifier during the dry season, heat the room or use AC to maintain acceptable humidity during humid summers.