In In practice moisture of wood is very important:

• Weight of logs and lumber
  
  
• Open-air drying and technical drying
  
  
• Formation of cracks / shakes during drying
  
  
• Humidity of the wood for application on the place of utilization
  
  
• Change of dimension trough absorption or dispensing of humidity
  
  
• Danger of fungal decay
  
  
• Exchange of humidity for a clean indoor climate

Water in wood

In contrary to hardwood, fresh chopped softwood contains in average 55-70 % of water - related to wood in dry state. Corn takes about 35-50 % and the sapwood 100-150 % water. Hardwood fresh from wood contains in average between 70 % and 100 % water based on dry wood.

Timber just chopped in wood is also called „green wood". It contains approximately the same moisture content like the living tree. But the moisture content of trees depends on place and type. The time of chopping trees is uninfluential to the moisture content.

The humidity content or the humidity of wood describe the water content in timber. It is indicated in per cent with the abbreviation u. Humidity of wood u specifies the proportion between amount of water mw within in wood and water free wood-substance m₀ (dry wood m₀). The amount of water in wood m_w can be calculated as follows:

Wood is firstly weighed in wet (wet weight mu) and later in dry (dry weight ) m₀. The difference between these both weights (m_u-m₀) is the existing amount of water mw in wood.

Quelle: Gesamtverband Deutscher Holzhandel / German Timber Trade Federation

Which humidity of wood for which place of utilization

For appropriate drying and usage of wood it is important to know a lot about the humidity balance of wood. Before working with the wood it should strictly dried to the humidity that corresponds with the balance of its future environment. As there is only the periodical fluctuation of the climate that acts on the wood the change in form through shrinkage and swelling can be kept quiet low. It is a big difference if you use wood for encasing outdoor or as floor indoor. Depending on the later usage you aim at different end-humidity - the so called reference humidity.

Humidity of wood for processing with different usages (valid for the middle of Europe):

If there is any default concerning reference-humidity, what means humidity of wood is adopted to further processing, there may appear consequential damages after emplacement or usage of the timber, for example: deformation in cross section, moving, slippage, cracking, mistakes with gluing, damage with lacquer and infestation of vermin.

Conclusion for practice: according to the DIN Norm wood should be dried to the adjusted humidity for the further usage, before leaving the manufacturing business, for example: carpentry or interior accessories.

Example:

Authority: Gesamtverband Deutscher Holzhandel / German Timber Trade Federation