Acclimation: WHY? Wood Equilibrium Moisture Content --Table And Calculator
Click on the link below to view the wood equilibrium moisture content calculator. It is designed to give the equilibrium moisture content of non-living wood, natural or cut, based on the data entered, at or below the fiber saturation point (about 30% moisture content) given the temperature and relative humidity. A new window will open.

Installed too dry for the geographical area of the home.

Calculator provided by

Hand-Held Moisture Meters Download PDF


  • Is the process of adjusting the wood flooring to the moisture level of its environment.
  • Wood takes moisture from the air and gives wood gives moisture to the air -- FOREVER!
  • The wood floor finish will "not" stop moisture from going in and out of the wood.
  • The wood will take on the same moisture content as the interior relative humidity.

What does that mean?

  • Let's say the basement is 60 degrees F with a relative humidity of 65%
  • The first floor is at 70 degrees F with a relative humidity of 50%
  • Our chart shows us that there would be almost a 3% moisture difference.

  • This is what a 3% difference between the top surface of the boards and the bottom of the boards can do!
  • The wood flooring should be acclimated to coincide to the normal expected interior environmental living conditions.

  • The average interior moisture content varies throughout the country. The Forest Products Laboratory moisture map provides a starting point to estimate your average yearly moisture range. The first number indicates the average interior moisture content in the month of January. The second number indicates the average interior content for the month of July. Your actual moisture contents may vary significantly from these figures.
  • Properly functioning central heating and air conditioning systems control a homes environment. But...These systems may be turned off during certain times of the year!
  • The wood flooring is then subjected to fluctuations in moisture content. Normal living conditions may vary throughout the year. During the dry seasons of the year the interior wood moisture content may be at 6%. During the humid seasons of the year the interior wood moisture content may be at 13%.

And this happens:

  • It is prudent to acclimate the wood flooring to the midpoint of the expected range of moisture changes throughout the year. The midpoint between 6% and 13% would be 9.5%.
  • Finish applied to the surface of the wood will "SLOW" changes in the wood’s moisture content. The water vapor must first diffuse through the coating. Three coats of most floor finishes will aid at excluding moisture for a few days but their effectiveness drops off dramatically over a couple of weeks.
  • A moisture retarder such as 15 pound building paper installed under the wood flooring will help "SLOW" the migration of moisture from beneath it.
  • "SHORT" fluctuations in relative humidity usually have no appreciable effect on wood moisture content. With prolonged exposure of weeks to months, the floor will eventually stabilize to the moisture content of the environment.