An Introduction to the Air Seasoning of Timber

(Note, much of the following relates to the industrial drying of sawn, square-edged timber, but the principles involved are also appropriate to the drying of wood in other forms).

At its simplest air seasoning of timber involves constructing stacks of sawn wood and leaving the stock to dry making use of the wind and the sun.

We have only limited control over the effects of the wind and the sun and this is effected via the correct placement and construction of the stack to be dried.

In Europe (though not in all countries in the world) we generally try to accelerate the drying process.

In Europe drying times are long. Approximate drying times are:-

Softwoods (spring start – softwoods can tolerate “rapid” drying)

· 1 inch: 30 - 100 days

· 2 inch: 100 - 120 days

Hardwoods (autumn start – hardwoods cannot tolerate “rapid” drying)

· 1 inch: 270 days

· 2 inch: 360 days

A serious limitation of air seasoning of timber in UK (and similar climates) is the minimum moisture content attainable, due to the prevailing climate. In winter only as low as 23% can be attained, whilst even in summer 17% is the lowest moisture content that can be obtained. These values are NOT LOW ENOUGH FOR MOST INDOOR APPLICATIONS. So in Europe we must also kiln dry for indoor applications.

Now Read about the Best Practices when Drying Timber in the Drying Yard.