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Timber Seasoning & Moisture Content of Timber

Timber seasoning is the process of removing moisture from timber to prevent it from warping or splitting when it’s used in construction. Typically, wood from a freshly cut tree contains 50% of moisture, which then begins to rapidly absorb once the wood is taken away from its source of nutrients. This can be unpredictable given there are a lot of environmental factors variations and can often result in timber either retaining too much moisture or drying too quickly. Timber seasoning allows for a controlled and predictable method of retaining the moisture content of timber, and for the wood to retain its dimensions and last longer.

There are two ways to season timber, each of which has its own pros and cons. We take a look at the different types of timber seasoning and why the moisture content of timber is so important.

Types of Timber Seasoning

Natural Seasoning of Timber

Natural seasoning of timber or ‘air seasoning’ works exactly how it sounds – the timber is left to dry naturally. Though slow to action, natural seasoning is an inexpensive way to dry wood as it relies less on machinery or heavy labour. Typically placed in a shed that has one or more sides open for airflow entry points, the timber is stacked using spacing sticks to allow the air to circulate freely. Depending on the thickness of the wood, the drying can take anywhere from three months to a whole year. Natural seasoning of timber relies heavily on weather conditions and can prove ineffective during the cold winter months. It can also be a little bit harder to precisely disperse the same amount of moisture content without, as some parts of the wood could be getting more air than others. However, some believe air dried timber retains its colour better and is easier to bend, which means it favourable for woodworkers.

Kiln Seasoning of Timber

Kiln seasoning is the most common form of timber seasoning as it’s a quick way of effectively drying wood. The timber is stacked on top of a trolley, which is then rolled into a kiln filled with steam jets and heating coils that absorb moisture from the timber. A vent and fan help circulate the air so that it’s evenly distributed throughout the timber. Kiln seasoning of timber also delivers exact moisture content, as every part of the timber receives the same drying treatment. 

Kiln seasoning of timber is usually divided into the following classes.

Progressive: The timber enters at one end and progressively moves through the building as the temperature and humidity increase.

Compartment: The timber remains in one place and the temperature and humidity is closely controlled. This method requires more skill from the operator but is good for timber that is difficult to dry or sensitive, such as refractory wood.

Why the Moisture Content of Timber Is Important

The moisture content of timber is important as the wrong amount of moisture can affect the performance and durability of the timber. Too much moisture, and timber will be unable to balance properly, and will be at increased risk of timber destroying diseases such as wood rot and fungi. Too little, and the timber is susceptible to breakage.  Of course, the acceptable moisture levels in wood vary, given the use of the timber. Fencing timber, for example, will have a higher moisture content as it’s in an environment where it’ll be exposed to wet elements.

Acceptable moisture content of timber common uses:

When it comes to choosing timber supplies, you can usually trust that fencing or hardwood timber bought from a reputable timber supply company will have the acceptable moisture content. Typically, these are the following acceptable moisture levels in wood.

Ideal moisture content for wood (uses):

Indoor wood objects:  6-8%

Wood flooring: 6-9%

Construction: 9-14%

Check out our rough sawn hardwood for the best timber for flooring, paneling and furniture.

 Moisture content for woodworking

If you’re interested in woodworking, the acceptable moisture content for woodworking ranges between 5-9%. Natural seasoning is commonly preferred in the woodworking community, as it tends to make the wood a little more pliable.

You can find out the moisture content of timber by purchasing a material moisture reader, or by asking your timber supplier.

Seasoned Timber Brisbane

We hope we’ve given you a clearer idea on timber seasoning and the ideal moisture content for wood uses. If you’d like more information on timber seasoning or need a quote on seasoned timber, contact us and a member from our wholesale timber supplies team will get in touch shortly.

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