Green Oak beams are cut from wet round wood, and directly off a saw. Green Oak is what has been used for buildings in this country for many centuries. This includes some of the greatest monuments such as Windsor Castle, the Palaces of Westminster, Canterbury Cathedral along with many others, were all constructed using what is known as Green Structural Oak.
The freshly sawn oak beams initially offer a golden-honey and warm colour. When the timber is un-oiled when used in the external applications, the wood will start to weather where it reaches a grey silver colour, while for applications internally, the colours will start to mellow. Oiling will however, alter the natural aging colours.
The structural Oak beams will be the straightest at the stage that they are freshly sawn. Oak is regarded as a highly durable material, which means even when it is anchored or weighted into position, it will attempt to twist and move. Gaining an understanding on how Oak behaves and the best way to work with these materials is essential when it comes to choosing the orientation of the beams, which also impacts on the overall performance of each beam.
The green Oak beams will never fully dry out, with the freshly sawn beams usually featuring a moisture-content of around 80%. This moisture content is still present in beams which have been in sue for over 300 years with a 25 to 35% moisture content in their centres. After a number of years in use, the outer 75mm of a square-section of 200mm green Oak beam may reach equilibrium.
What this means is that when the green Oak beams are first milled they look close to perfect. When the outer-faces begin to dry, the timber’s character starts to show up as splits open and knots start to show which is linked to shrinkage that is commonly associated with drying.