Wood - Durability

Wood is a rigid plant tissue whose exceptional mechanical properties have enabled trees to become the world's largest and longest-lived living creatures.

Like all natural organic matter, wood is biodegradable, and when the tree dies, it is decomposed by fungi and forest microfauna, allowing elements to be recycled. Building sustainably with wood means taking advantage of wood's technological qualities by preventing it from decomposing as much as possible.

A good understanding of the biology of decomposing organisms is essential for effective, targeted control of agents that could mechanically weaken the material. Few living beings are capable of digesting wood. These include fungi, beetles, termites, molluscs and crustaceans.

Depending on the conditions under which the wood is used, and in particular the risk of wetting, the biological risks are not the same. To guarantee the longevity of our structures and products, we must first and foremost limit the risk of humidification by careful design. These measures are part of a constructive prevention approach that has proved its worth over the centuries, and whose effectiveness can still be seen in some older buildings.

There's no such thing as rot-proof wood. All woods are biodegradable, but biodegradation takes varying degrees of time depending on the species. The natural durability of certain woods against fungi and insects is mainly due to the presence of extractable chemical compounds. The judicious choice of the right wood species according to biological risks and the expected service life of the structure is one of the first steps in the wood preservation process.

Chemical treatment should be considered as a last resort, to give the material greater durability if necessary. For sheltered woods, a surface treatment is often sufficient, and in the case of non-durable woods such as spruce and fir, obligatory in the case of structural wood. For wood exposed to the elements, in-depth treatment is required, and can only be carried out on wood that is sufficiently impregnable, since impregnability is a property closely linked to anatomy.

The aim of preservation is to maintain the structural integrity of the material. Preservation of appearance is the task of wood finishing. Preservation and finishing have different objectives and should not be confused, even though they influence each other.