Summary

One of the most important factors affecting the performance and properties of wood is its moisture content. The amount of water present in wood can affect its weight, strength, workability, susceptibility to biological attack and dimensional stability in a particular end use.

We estimate that over 80% of the in-service problems associated with wood are in some way related to its moisture content. The importance of the interaction between water and wood cannot be understated and, if not properly understood and taken into consideration, can result in the need for expensive remedial measures.

This Wood Information Sheet provides basic information for the specifier and user on the facts and importance of the moisture content of wood. It considers drying, shrinkage and movement, including movement values for some common species, and also looks at measuring moisture content, particularly the use of moisture meters.

Key Information

The amount of water contained in a piece of timber is known as its ‘moisture content’ (MC).

In constant conditions of temperature and relative humidity, timber will eventually reach a constant moisture content – the ‘equilibrium moisture content’ (EMC).

As it loses water below the 25%-30% fibre saturation point it will shrink laterally. Timber does not shrink or swell lengthwise along the grain.

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