What is green oak timber?

Green oak timber is a natural, organic material. By its very nature, green oak wood shrinks and moves as it matures and dries. Predicting shrinkage in green oak wood is of paramount importance throughout the design, manufacture and building process. Welsh Oak Frame are highly skilled in factoring in the movement and shrinkage which occurs within the oak frames. This ensures that the structure remains structurally sound throughout its lifetime.

Why does green oak shrink and sometimes split?

When a tree is felled it has a high moisture content. In some cases up to 80%. A dry piece of oak inside a building can have a moisture content as low as 8%. Initially during the drying out process the timber loses what is known as ‘free water’ from its cell cavities. Once this has gone the timber is said to have reached it fibre saturation point, which in oak is around 30%.

What’s important to remember is that the splitting and cracking of the oak timbers is not a flaw. They are in fact becoming stronger and harder whilst this natural process occurs. When we take a client to view one of our homes, they are often naturally drawn to the imperfect features of the oak.

Most shrinkage occurs within the first twenty-four months. Generally the most drastic problem you are likely to encounter is small shrinkage cracks between the oak framework and the plastered infill panels internally. This is easily remedied when routine re-decoration takes place.

Why use green oak for construction?

Green oak timber is the only way forward when it comes to oak frames, roof trusses, beams and posts. The soft wood is easier to cut and shape to exact sizes. More importantly, as the green oak timber starts to dry, it shrinks slightly – mostly across the width of the grain – tightening the joints and hardening to improve the overall strength of the oak frame.