(continued)
Equalizing the Moisture Content
A porous material with a natural cellular structure, wood expands and contracts depending on the amount of
moisture present in the surrounding atmosphere. Proper acclimation of flooring before installation is necessary to
avoid excessive cracks between planks, and in extreme cases, cupping and lifting of the floor.
While all wood will eventually acclimate to its environment, it is very important to determine the moisture equilibrium
point of each installation. Using the equilibrium moisture content chart below, determine the proper moisture
content for the installation. Always use a moisture meter to determine where the flooring and present job-site
conditions are in relation to the projected final equilibrium point. Finally, monitor the flooring and job-site conditions
as they acclimate.
The moisture content of wood below the fiber saturation point is a function of both relative humidity and
temperature of the surrounding air. If the wood is neither gaining nor losing moisture, an equilibrium condition has
been reached. The relationship between equilibrium moisture content, relative humidity, and temperature is shown
in the following chart.
Equilibrium Moisture Content Chart
Temp. Relative Humidity, Percent
5 101520253035 4045 50556065 7075 80859095 98
30° F 1.4 2.6 3.7 4.6 5.5 6.3 7.1 7.9 8.7 9.5 10.4 11.3 12.4 13.5 14.9 16.5 18.5 21.0 24.3 26.9
40° F 1.4 2.6 3.7 4.6 5.5 6.3 7.1 7.9 8.7 9.5 10.4 11.3 12.4 33.5 14.9 16.5 18.5 21.0 24.3 26.9
50° F 1.4 2.6 3.6 4.6 5.5 6.3 7.1 7.9 8.7 9.5 10.3 11.2 12.3 13.4 14.8 16.4 18.4 20.9 24.3 26.9
60° F 1.3 2.5 3.6 4.6 5.4 6.2 7.0 7.8 8.6 9.4 10.2 11.1 12.1 13.3 14.6 16.2 18.2 20.7 24.1 26.8
70° F 1.3 2.5 3.5 4.5 5.4 6.2 6.9 7.7 8.5 9.2 10.1 11.0 12.0 13.1 14.4 16.0 17.9 20.5 23.9 26.6
80° F 1.3 2.4 3.5 4.4 5.3 6.1 6.8 7.6 8.3 9.1 9.9 10.8 11.7 12.9 14.2 15.7 17.7 20.2 23.6 26.0
90° F 1.2 2.3 3.4 4.3 5.1 5.9 6.7 7.4 8.1 8.9 9.7 10.5 11.5 12.6 13.9 15.4 17.3 19.8 23.3 26.0
100° F 1.2 2.3 3.3 4.2 5.0 5.8 6.5 7.2 7.9 8.7 9.5 10.3 11.2 12.3 13.6 15.1 17.0 19.5 22.9 25.6
From the U.S. Dept. of Agriculture “Wood Handbook — Wood as an Engineering Material”
Wood in service usually is exposed to both long-term (seasonal) and short term (daily) changes in the relative
humidity as well as surrounding air temperature. Thus, wood virtually always is undergoing at least slight
changes in moisture content. These changes usually are gradual, and short-term fluctuations tend to influence
only the wood surface. Moisture content changes may be retarded using protective coatings, including varnish,
lacquer or paint.
52
(800) 525-BR111(2711)
•
Fax (800) 577-2711
•
www.br111.com
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Indusparquet
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8/30/04
