Five Use Classes for Different Moisture Environments

This guide explains the specific moisture environments for all five Use Classes in EN 335:2013. These refer to the the panel’s suitability for different moisture exposure,  Service Classes refer to its moisture content, see more.

APA plywood panels appropriate for Use Classes  1, 2 and 3. This is also currently applicable to LVL.  APA OSB is suitable for Use Classes 1  and 2.

Use Class	Impact of Specific Moisture Environments
1	Little risk of attack by surface moulds, staining moulds or wood-destroying fungi. Attack by wood-destroying insects, including white ants or termites is possible although the likelihood depends on location.
2	Moisture content can occasionally increase allowing wood destroying fungi to grow. Disfigurement can also occur due to the growth of surface moulds and staining fungi. There is a possibility of attack by wood-boring insects, including termites, depending on geographical location.
3	Moisture content can frequently be above 20% making the product vulnerable to attack by wood-destroying fungi. Disfigurement is possible due to the growth of surface moulds and staining fungi. There is a possibility of attack by beetles and termites.
4	Moisture content will be permanently above 20% leading to attack by wood-destroying fungi and disfiguring fungi. Attack by wood-boring insects, including termites is possible although the likelihood depends on geographical location.
5	Where material is permanently above 20% moisture content and wholly or partially submerged in salt water, attack by marine organisms is the main problem. Attack by wood-destroying fungi and growth of surface moulds and staining is also possible particularly for those parts above water.