Why wood is dried
Drying largely removes defects associated with moisture in wood and improves its properties in use. Dried wood is stronger and more resistant to the action of destructive fungi.
Moisture content for joinery and construction products
Technical conditions list the following moisture values for joinery and construction products:
| Product or element | Moisture content |
|---|---|
| Window boxes, window sashes, door frames and window boards | 10% |
| Boxes of interior doors and windows | 10% |
| Boxes of exterior doors and windows | 10% |
| Door leaves made of panels and boards | 10% |
| Frame elements | 10% |
| Floor battens and boards, perimeter floor strips and thin strips | 10–13% |
| Exterior cladding and profiled strips | 13–15% |
Consequences of increased moisture
Joinery and construction products made from wood with increased moisture content will inevitably dry out, warp and crack, while the product itself will lose its strength.
For this reason, wood used in construction must be dried to the moisture content prescribed by the technical conditions.
How the drying process works
Drying consists of air, heated to a specified temperature, flowing around all sides of the wood being dried and removing moisture from it.
During drying, the outer part of the material dries faster than the inner part. Moisture therefore moves from the wetter zone towards the drier outer zone of the material.
Drying is consequently a process in which moisture moves from the centre of material with higher moisture content towards its periphery with lower moisture content.
Natural and artificial drying
Wood drying is divided into natural and artificial drying.