By Grete Heimerdinger, Lignomat
Nobody would worry about moisture and humidity if absorption and loss of moisture were not accompanied by serious wood floor problems. Changes in moisture content bring with it dimensional changes. Floor planks shrink, warp, cup, crown, show cracks, etc., which make the homeowner call the installer or the manufacturer asking for remediation.
The first step in preventing any moisture problems is to know, what cause changes in moisture content.
Below is the EMC chart, which ties moisture content and humidity together. Values of humidity and moisture shown below are conditions, when the moisture content will not change. The italicized area marks the permissible range for floors: If the relative humidity stays between 30-50%, and the wood moisture stays between 6-9%, only minor dimensional changes are expected. Special precautions are necessary for floor installations if those values cannot be kept. For instance, in the high desert climate of Colorado low relative humidity can cause problems. In the moist and warm climate of Florida, high relative humidity must be kept in check.
At the start of the floor project, the floor installer on-site is responsible to find out if the right conditions for a successful installation are met. Moisture content and relative humidity should be measured. Next, compare the values with the EMC chart below. The building owner should be advised if the relative humidity conditions are not within the permissible range. If the moisture content of the wood is not within the desired range, the company providing the wood floor has to be contacted.
If all is ok, the installation can proceed. After completing the installation, document the condition of the floor (using the moisture meter and thermo-hygrometer again) in the final report and advise the customer to keep the relative humidity within the recommended range. If moisture problems occur later, the values in the final report can help the inspector to find the source of the problems.
| Relative Humidity EMC Table | |||||||||||||||||||
| T °F | 5 | 10 | 15 | 20 | 25 | 30 | 35 | 40 | 45 | 50 | 55 | 60 | 65 | 70 | 75 | 80 | 85 | 90 | 95 |
| 30 | 1.4 | 2.6 | 3.7 | 4.6 | 5.5 | 6.3 | 7.1 | 7.8 | 8.7 | 9.5 | 10.4 | 11.3 | 12.4 | 13.5 | 14.9 | 16.5 | 18.5 | 21.0 | 24.3 |
| 40 | 1.4 | 2.6 | 3.7 | 4.6 | 5.5 | 6.3 | 7.1 | 7.8 | 8.7 | 9.5 | 10.4 | 11.3 | 12.4 | 13.5 | 14.9 | 16.5 | 18.5 | 21.0 | 24.3 |
| 50 | 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 |
| 60 | 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 |
| 70 | 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 |
| 80 | 1.3 | 2.4 | 3.5 | 4.4 | 5.3 | 6.1 | 6.8 | 7.6 | 8.3 | 9.1 | 9.6 | 10.8 | 11.7 | 12.9 | 14.2 | 15.7 | 17.7 | 20.2 | 23.6 |
| 90 | 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 |
| 100 | 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 |
