Moisture in timber

Date Published

17 August 2022

Document Type

Category

Author

TRADA
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.

Case studies

To the architect, Maggie’s Oldham is a deliberate exemplar of how to create a fresh, uplifting and caring environment while eliminating the use of harmful materials.

The new visitor centre replaces facilities – community room, shop, restaurant and exhibition areas – formerly housed in buildings which have now been redeveloped to provide a cycle centre; the centre also aims to improve and develop the forest as a regional centre of excellence for sustainable economic activity.