Section Contents

 Service Classes and their  Corresponding Use Classes

 Service Class according to Eurocode 5  Possible corresponding Use Class according to EN 335:2013

Service Class 1

Is characterised by a moisture content in the material corresponding to a temperature of 20°C and the relative humidity of the surrounding air only exceeding 65% for a few weeks per year.

 

NB The average moisture content in most softwoods will not exceed 12%

Use Class 1

Situations in which the wood or wood-based product is inside a construction, not exposed to the weather and wetting. Attack by disfiguring fungi or wood-destroying fungi is insignificant and always accidental. Attack by wood-boring insects, including termites, is possible although the frequency and importance of the insect occurrence depends on the geographical region.

 

Service Class 2

Is characterised by a moisture content in the material corresponding to a temperature of 20°C and the relative humidity of the surrounding air only exceeding 85% for a few weeks per year.

 

NB The average moisture content in most softwoods will not exceed 20%.

Use Class 1

As above.

 

Use Class 2 – if the component is in a situation where it could be subject to occasional wetting caused by e.g. condensation.

Situations in which the wood or wood-based product is under cover and not exposed to the weather, particularly rain and driven rain, but where occasional, but not persistent, wetting can occur. Condensation of water on the surface of wood and wood-based products may occur. Attack by disfiguring fungi and wood-destroying fungi is possible. Attack by wood-boring insects, including termites, is possible although the frequency and importance of the insect risk depends on the geographical region.

 

 

Service Class 3

Is characterised by climatic conditions leading to higher moisture content than in Service Class 2.

 

Use Class 2

As above.

 

Use Class 3 or higher if used externally

Situations in which wood or wood-based product is above ground and exposed to the weather, particularly rain. Attack by disfiguring fungi and wood-destroying fungi is possible. Attack by wood-boring insects, including termites, is possible although the frequency and importance of the insect risk depends on the geographical region. A large variety of in-use situations exists and, when relevant, Use Class 3 may be divided into two sub-classes – Use Class 3.1 and Use Class 3.2.

 

Use Class 31

In this situation the wood and wood-based products will not remain wet for long periods. Water will not accumulate.

 

Use Class 3.2

In this situation the wood and wood-based products will remain wet for long periods. Water may accumulate.

 

Notes:

For plywood and LVL, guidance on some factors affecting durability can be found in DD CEN/TS 1099.

In Use Class, the performance the performance of most plywood may be compromised if suitable preservative treatment and/or relevant surface and edge coating is not applied and if the panels are not properly maintained and installed.