The MOISTURE CONTENT MAP shows average moisture contents in Winter and Summer by geographic areas.

(i.e.) If flooring is installed in buildings along the Gulf Coast it can be expected to eventually acclimate between 11% and 13% moisture content.

(i.e.) Flooring installed in the Western Rockies can be expected to eventually acclimate between 4% and 8% moisture content.

These moisture contents are based on the average seasonal conditions. Excessively dry or excessively wet conditions can further influence the changing moisture content of flooring.

Interior environmental controls which continually provide stable temperature and relative humidity, will also effect the final moisture content of flooring.

The RELATIVE HUMIDITY & EMC TABLES can help predict the influence of the immediate environment.

Other influencing factors can be excessively wet or excessively dry materials and/or areas, during distribution and at the job site.

SHRINKAGE EXPANSION

-WOOD           is a hygroscopic material. This means when wood is exposed to air, it will dry or pick up                          moisture until it is in equilibrium with the humidity and temperature of the air.
-MOISTURE  bsorption causes wood to swell.

-MOISTURE    loss causes wood to shrink.

-SHRINKAGE begins at 25-30% moisture content, the fiber saturation point. Shrinkage continues to                           0%  moisture content, an oven dry state.

-SWELLING   occurs as wood gains moisture. Swelling occurs from 0% to 25-30% moisture content,                           the fiber saturation point.

-WOOD      does not shrink or swell equally in all directions.
-WOOD      changes approximately:
                         0.1%- Along the grain (longitudinally)
                         2% to 8%- Across the grain & across the annular rings (radially) Quarter sawn
                         5% to 15%- Across the grain & parallel to the annular rings (tangentially) Plain Sawn

The DIMENSION CHANGE CHART shows the average change, in inches, or ¾" x 2 ¼" Oak Strip Flooring in the tangential, Plain Sawn, direction, as the moisture content changes.

If a ¾" x 2 ¼" Oak Strip is exposed to an environment which changes the moisture content by 4% (i.e. from 7% to 11%) the strip may SWELL as much as 1/32 of an inch.

The opposite is also true, if a 2 ¼" Strip begins at 11% moisture content and loses moisture to 7% moisture content, the strip may shrink as much as 1/32".

Remember, NOFMA Members' Hardwood Flooring is manufactured at 6%-9% moisture content with a 5% allowance outside this range. If the job site conditions change this range, or the geographic area is expected to change this range, it is the responsibility of those who handle and use the product to provide for and be informed of the eventual changes which can be expected.

Generally, flooring is expected to SHRINK in dry climates and EXPAND in the wetter climates.

HOW MUCH depends on your particular area and individual construction practices.

EQUILIBRIUM MOISTURE CONTENT HERE