This is an area where you will get many different answers. The reason is that there is no single true answer, only guidelines. Another reason is that there are people living by selling wood, who then will provide different answers based on what they have to sell. The major reason for the different answers is that there is a lot of dependencies:
- The history for the dryness of wood is an important part of the answer (and you will not likely get to know the history unless you are talking expensive wood)
- The current air humidity and the last months of air humidity
- The thickness of the wood
- The type of wood
- What level of air humidity that is normal where you live
- What you are going to use it for.
Common recommendations about wood moisture content depending on what it is to be used for:
- inside wood working around 10-15% moisture content
- furniture building around 6-10%
Wood strive to have a moisture content which is in equilibrium with the air. Thus, if you are in the summer with above 70% relative air humidity and find wood that is as dry as is often recommended for furnitures (around 6-10%), you have found wood which has not been in that air for a long time. On the other hand, in the winter with a relative air humidity around 30%, you can be lucky and find wood which has a moisture content slightly above 6% and which is still drying for its first time.
In order to answer the question on what moisture content your wood should have, you need to adjust above recommendations based on what moisture content your air normally has.
- In cold climates in the beginning of spring, you should be able to find wood which already in the lumber yard is at, or close to, the furniture dry range above. In the diagram above you see that the top dark blue line, depicting drying wood, is below 10% when relative humidity in air is below around 40%. Thus, where climate is cold, finding dry wood in ordinary lumber yards should be possible part of the year
- In the beginning of autumn, you should for most areas in the world expect all wood not specifically bought as furniture dry to have a moisture content above the furniture dry interval. In the diagram you see that the bottom light blue line, depicting wood absorbing humidity, is above 12%. Thus, you could use that wood if you just thought it had been drier before.