Wood is a dynamic material. Simply put wood will change dimension in relation to the surrounding humidity levels. In humid conditions wood flooring will absorb moisture and swell in periods of dry conditions or low humidity like winter or the heating season wood will lose moisture and shrink.

Quality wood flooring is kiln dried to a moisture content of 6 to 8% this translates to an ambient humidity level of 45% Bottom line, if the environmental relative humidity is 45% the wood floor is stable it will not shrink or swell because it isn’t absorbing or loosing moisture.

Many people mistakenly think they just need to let flooring sit for a week or two and they are ready to install. In truth some floors are ready to install the moment they’re delivered. To allow a floor to sit at a job site under extreme conditions of excessive humidity or conversely excessively low humidity that don’t reflect “Normal living conditions” will in fact do more harm than good.

The key point to remember is not that acclimation is good or bad rather the installer needs to understand the dynamic relationship between water/humidity and wood and make an educated judgment for when and how much acclimation is required.

It is the owner’s responsibility to insure proper control of humidity for the long term. Keeping in mind your optimal target humidity level is 40 to 45%

Some quick rules of thumb.

The job site should be ready for the wood to be delivered “Normal living conditions”
The site should be fully closed, doors and windows in place
Climate controls should be in place and operational 48 hours prior to delivery
All wet trades ie. Plaster, Painting and Tile should be complete and dry prior to delivery
In the heating season if you see gaps developing you will need to increase the humidity levels consider installing a humidifier
During periods of high humidity your floor is absorbing moisture de-humidification is recommended.
A realistic humidity range is between 40 and 60% relative humidity.