Wood moves and warps making it the ultimate active construction material. It contracts when dry and expands when wet.
When used outdoors, wood moves according to the balance between the ambient humidity and its own level of humidity.
There are two wood board drying methods:
AD or air-dried::Residual moisture content is generally above 18%.
During dry periods or in summer, AD wood boards contract and lose part of their moisture to match the ambient humidity. Spacing between deck boards would then increase.
To avoid abnormally large gaps between boards, we recommend hardWood Clip™ Extreme™ fasteners when installing AD wood boards.
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Conversely, during wet periods or in winter, KD wood boards will swell and expand due to their higher moisture content until they reach the ambient humidity. Spacing between the deck boards will then decrease. Under the same conditions, AD wood boards are closer to the ambient humidity and may only move slightly due to their higher moisture content.
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The moisture content of deck boards should always be tested prior to installation using a properly calibrated probe moisture meter. It will determine the board spacing required during installation to allow for expansion and contraction between wet and dry periods.
KD wood boards |
AD wood boards |
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*For narrow boards and unstable wood only
