Finnforest UK


appendix 1   


hazard classifications
European Standard for the assessment of Hazard classes: Application to solid wood (source EN 335-1, EN 335-2)

Hazard class 1
Where wood is under cover, fully protected from weather and not exposed to wetting.

In this environment the moisture content of solid wood is such that the risk of attack by surface moulds or by staining or wood destroying fungi is insignificant, that is the wood shall have a moisture content of maximum 20% in any part for practically the whole of its service life.  However, attack by wood boring insects, including termites, is possible although the frequency and importance of the insect risk depends on the geographic region.

Hazard class 2
Where wood is under cover and fully protected from the weather but where high environmental humidity can lead to occasional but not persistent wetting.

In this environment the moisture content of solid wood occasionally exceeds 20% either in the whole or only in part of the component and thus allows attack by wood destroying fungi.  For timber whose use includes a decorative function, discolouration can also occur as a result of the growth of surface moulds and staining fungi.

Hazard class 3
Where wood is not covered and is not in contact with the ground.  It is either continually exposed to the weather or is protected from the weather but subject to frequent wetting.

In this environment solid wood can be expected to have a moisture content above 20% frequently, and thus it will often be liable to attack by wood destroying fungi.  For timber whose use includes a decorative function, discolouration can occur as a result of the growth of surface moulds and staining fungi.

Hazard class 4
Where wood or wood-based product is in contact with the ground or fresh water and is permanently exposed to wetting.

In this environment solid wood can have a moisture content above 20% permanently and is liable to attack by wood destroying fungi.  Termite can be a problem in certain geographic regions.  Additionally, the above ground (or above water) portion of certain components, for example fence posts, may be attacked by wood-boring beetles.

Hazard class 5
Where wood is permanently exposed to salt water.

In normal conditions external cladding is exposed to hazard class 2 or 3.