Hardwood Flooring and Acclimation  

All woods, some more than others, react to moisture by expanding when moisture is added to it or by shrinking or contracting when moisture is removed. 

The purpose of acclimating wood flooring before installing it is to allow the moisture content of the wood to adjust to "normal living conditions" at the site--that is, the temperature and humidity conditions that will typically be experienced once the structure is occupied.

Thus, it does no good at all--in fact, it is likely harmful--to store wood flooring at the jobsite under conditions that don't reflect those normal environmental conditions.

The wood flooring industry has done a good job in recent years communicating the message that wood flooring is a dynamic material subject to changes in dimension as a result of changes in humidity in the surrounding environment.  That has led to increasing awareness of the need to acclimate wood flooring before installation.  Unfortunately, some installers have heard the message as, "leaving wood flooring at the jobsite for two weeks will properly acclimate the wood, no matter what the conditions are."

In truth, some wood flooring may already be at the proper moisture content when it's delivered.  To allow it to sit at the jobsite under excessively humid conditions will only cause the flooring to absorb unwanted moisture.

Different cuts of wood will also play a part in the amount of reaction to moisture.  Normally plain sawn (horizontal grain) reacts about twice as much as riff sawn (vertical grain or quartersawn).  The width of a board also can also affect stability of a floor i.e.; a 3" wide board will shrink or expand half as much as a 6" wide board. 

So, the key message is not that acclimation is good, and that's all you need to know.  Rather, installers need to understand the dynamics of water and wood and make educated judgments about when and how much acclimation is required.  To do so requires knowing what the moisture content of the flooring is at the time of delivery and what its expected moisture content will be "in use."

In Alaska, with the long heating season, acclimating the flooring before installation and the use of a humidifier incorporated into your heating system will keep the home climate more consistent year around and thus help eliminate any seasonal reaction of the flooring.