When wood is to be used as a construction element, three choices have to be made, based on the location of the wood and its climatic exposure, to preserve its integrity and beauty over time. The first choice is the type of timber to use, the second is giving it adequate protection at the time of construction and, if the first two are not enough, the correct chemical treatment must be selected.
All wood is not the same.
The most commonly used material in carpentry is conifer wood from such trees as pine, fir and larch, used mainly for covering features. Without proper protection, these types of wood are subject to attack from fungus and organisms that may cause discolouration and rot. It is therefore essential to use protective products containing active ingredients preventing attack by biological agents.
Hardwood from such broad-leaved trees as oak, chestnut and beech are by nature more resistant to parasite attack, but they too, if exposed to a great deal of damp, can be ruined by fungus and insects. This makes it advisable to apply a protective treatment against fungus and wood-boring insects.
Tropical woods are the most resistant of all, such as teak, ipê, massaranduba, bangkirai and meranti, which are immune to fungus attack. These woods just need surface protection against dirt, stains and dust.
The standard EN 350 lays out a table showing the classification of the various types of timber according to their natural durability on a scale of 1 to 5. For example, we find teak, used for high quality garden furniture and decking, in Class 1 (high durability), while pine is Class 4 (poor durability). Moreover, the hardest part of the trunk of a tree is the central part, known appropriately as heartwood, while toward the outside is the less durable sapwood. Knowledge of the properties of the wood can determine the lifetime of the construction.