What is Acclimation . . .

Acclimation seems to be a confusing issue for most of us, but in actual fact it is not all that complicated.

All exotic and domestic wood flooring is a hygroscopic material, which means it can gain or lose moisture. The amount that this happens is dependant on the surrounding conditions of relative humidity. In very humid conditions the wood flooring will gain moisture and swell, in dry conditions the wood flooring will lose moisture and shrink (this causes the gaps associated with the heating season). In an attempt to stabilize the wood flooring before it is installed, the thinking has been that the wood flooring should be allowed to sit in the house for a period of time and allowed to come into balance with the relative humidity of the house (acclimation).

In order to truly achieve acclimation properly and thoroughly the wood flooring must be taken out of it’s wrapping and spread out around the house or stacked with spacers between each layer and then monitored with a moisture meter until the amount of moisture in the wood flooring is stable. Generally this is not practical on a construction site, and with the large percentage of wood flooring being prefinished all the handling can lead to quite a bit of damage to the finish.

Quality wood flooring is manufactured to a moisture content in the wood, of between 6-8% (i.e. the ratio of water to woody material is 6-8%). This corresponds to the wood flooring being in a house with 40-45% relative humidity, therefore if the house is climate controlled to a 40-45% R.H. the flooring can be installed without lengthy acclimation times. As long as the conditions in the house remain at 40-45% R.H. (generally the most comfortable conditions for people also) the wood flooring will be stable and no gapping or swelling will occur.

It will be up to the installer to determine that the right conditions exist to go ahead and install, but it will be up to the home owner to maintain the proper control of humidity in the house for the long term. If in spring/summer you allow the high humidity to spike, the wood flooring will start to swell, conversely if you allow the house to get too dry in the winter heating season the wood flooring will start to shrink and gaps will appear. This cycle will eventually lead to loosening of some nails and is the main cause of squeaky boards.