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Understanding Acclimation for Wood Block Flooring

The purpose for acclimating block is to allow the moisture content of the wood to adjust to normal conditions...that is the temperature and humidity that will be typical once the facility is opened...and the permanent Heating, Ventilating and Air Conditioning (HVAC) system is up and running.

Acclimation must include de-palletization or removal of all blocks from cartons or boxes, making a loose pile of the blocks. The lower the pile...the more spread out, the faster the acclimation. The higher the pile, the less spread out, the slower.

If conditions are not "normal", acclimation may be harmful. For example, if the humidity were too low, acclimation might artificially dry the block too low. In so doing, you might install the block too dry during the heating season, and have problems during the more humid months.

If you know the EMC or Equilibrium Moisture Content of wood in your region, it might be that the wood (block) brought to a jobsite might already be at the proper moisture content, and therefore acclimation for any length of time may not be necessary. Therefore, the determination of the length of acclimation time should be made by an installer who understands the dynamics of water and wood. To do so requires knowing and recording the moisture content at time of delivery, and what the expected moisture content will be.

At equilibrium moisture content wood neither gains nor loses water because it has reached equilibrium with the vapor pressure of the surrounding atmosphere. Changes in relative humidity and temperature of surrounding air cause both seasonal, long term and daily, short-term changes in the moisture content of wood. Long-term changes are gradual as moisture slowly penetrates the wood, while short-term fluctuations influence only the wood surface. Protective coatings slow the changes in moisture content, but ultimately the wood will be in equilibrium.

However, we always recommend at least 2 days of acclimation prior to installation. We never deliver and install block flooring on the same day. Please call us and we'll explain further.

Before wood blocks are delivered, the jobsite must be checked to determine if it is ready. The structure should be fully enclosed, with doors and windows in place, and interior climate controls operational for at least 48 hours to stabilize the moisture conditions of the interior. Wood flooring should not be delivered until plastering and painting are completed and dried.

We are questioned about the humidity or relative humidity being too high or too low.

Relative humidity maintained above 60-70% at normal residential temperatures can adversely affect wood components.
Humidity sustained at or above this level can result in an Equilibrium Moisture Content of 12% or more with associated expansion. Relative Humidity maintained at or below 25% to 30% can adversely affect wood components and result in an Equilibrium Moisture Content below 6%. This condition can cause greater than normal shrinkage with associated cracks.
(Wood Handbook U. S. Department of Agriculture, Forest Products Laboratory).

Ideal conditions for the installation of All Wood Flooring would be to acclimate and install at the average of the high end and the low end of the humidity spectrum, which we hope would be in the 35-50% range. We would be pleased to discuss with you length of acclimation for your particular installation. Don't hesitate to call us. Phone: 508-879-1500, Email: 

Shrinkage Cracks in Wood Block Flooring

There is no official "standard" for determining contraction tolerances for Wood Block installations. Kaswell Flooring Systems has established a standard of 3% as the amount of contraction that could be expected for most Wood Block installations, and should be considered normal. To determine percentage shrinkage, measure all voids, add them, and take them as a percentage of the flooring, 10 feet in two directions. If our block flooring is properly installed, shrinkage after installation should appear uniformly, and can provide a natural space for future expansion. Only re-filling and re-sealing should restore the flooring to a like new condition.