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SESK: Stuff Everyone Should Know · sesk.info/wood-equilibrium-moisture

What is equilibrium moisture content (EMC) of wood?

The moisture level where wood is neither gaining nor losing moisture.

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  1. The level where it neither gains nor loses moisture ✔
  2. The level where the board is fully dry
  3. The level where cell walls just fill with water

Why: Wood slowly trades moisture with the air until it matches the humidity and temperature around it. At that balance point it stops changing. Let boards sit in your shop to reach it before milling.

Huh, didn't know that: The handbook ties a board's moisture content to both relative humidity and air temperature.

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References

Answer: The level where it neither gains nor loses moisture. Wood slowly trades moisture with the air until it matches the humidity and temperature around it. At that balance point it stops changing. Let boards sit in your shop to reach it before milling.

  1. Wood Handbook: Wood as an Engineering Material, FPL-GTR-282 (USDA Forest Products Laboratory, 2021) research.fs.usda.gov/treesearch/62200
    Equilibrium moisture content (EMC) is defined as that moisture content at which the wood is neither gaining nor losing moisture.
    Checked 2026-10-10.

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