The Facts about Green Oak
What is Green Oak; it’s certainly nothing to do with its colour or a reference to recently cut and felled timber. Broadly speaking, and there is no official definition, Green Oak has a high moisture content and Dry Oak a low moisture content and this influences how, where and when the timber is used.
Within the oak tree, free water is retained in the cell cavities and bound water is contained within the cell walls.
Fresh oak is high in both types of water. At the point where all free water is lost but bound water is still retained, the timber is at fibre saturation point. In the case of oak this equates to a moisture content of 30%. Below the fibre saturation point the timber is losing bound water and to that extent could be said to be dry.
This is where the timber will shrink and twist and the grain open up in splits. Oak will naturally dry in air down to 18%. To get below this it would need to be kiln dried. Moisture content will vary depending upon surrounding conditions. For example it will continue to dry in a centrally heated environment and absorb moisture in damp conditions.
Green oak is used because larger section oak is either extremely expensive, often unavailable and it’s easier to work with. How the drying process is controlled is a matter of skilful selection by experienced graders; appropriate design, detailing and expert craftsmanship is needed.
What is Green Oak; it’s certainly nothing to do with its colour or a reference to recently cut and felled timber. Broadly speaking, and there is no official definition, Green Oak has a high moisture content and Dry Oak a low moisture content and this influences how, where and when the timber is used.
Within the oak tree, free water is retained in the cell cavities and bound water is contained within the cell walls.
Fresh oak is high in both types of water. At the point where all free water is lost but bound water is still retained, the timber is at fibre saturation point. In the case of oak this equates to a moisture content of 30%. Below the fibre saturation point the timber is losing bound water and to that extent could be said to be dry.
This is where the timber will shrink and twist and the grain open up in splits. Oak will naturally dry in air down to 18%. To get below this it would need to be kiln dried. Moisture content will vary depending upon surrounding conditions. For example it will continue to dry in a centrally heated environment and absorb moisture in damp conditions.
Green oak is used because larger section oak is either extremely expensive, often unavailable and it’s easier to work with. How the drying process is controlled is a matter of skilful selection by experienced graders; appropriate design, detailing and expert craftsmanship is needed.
Where to buy green oak buildings
- Welsh Oak Frame - Belmont Yard, Station Road, Caersws, Powys, SY17 5EQ, 01686 688000