Reading a wood moisture table
Wood keeps trading moisture with the air until the two reach a balance. That balance is the equilibrium moisture content, and it depends mostly on relative humidity and, to a lesser degree, on temperature.
The numbers below are approximate, for air at about 20 °C.
| Relative humidity, % | Moisture content, % | Typical place |
|---|---|---|
| 30 | 6 | Heated room in winter |
| 40 | 8 | Dry living space |
| 50 | 9 | Average living space |
| 60 | 11 | Humid summer day |
| 70 | 13 | Unheated workshop |
| 80 | 16 | Damp shed or cellar |
What to do with it
Furniture that will live indoors does best when the wood is brought to about 6 to 9 percent. If the lumber comes from a yard at 14 percent, expect it to shrink once it moves into a heated house, and expect joints to open with it.
- Stack new boards with thin sticks between them for a couple of weeks in the room where the piece will live.
- Check with a pin meter, and test the middle of the board, not the end.
- Cut and glue only when the readings stop changing.
Moisture meters read differently on different species, so treat a single number as a hint and the trend as the answer.