End uses

The NTR wood quality system makes it easy to select the right product for the intended use, which supports an economical and sustainable use of wood in the construction project.

The table below describes the use class according to European standard EN 335 and how this relates to the NTR wood protection classes.

Use class EN 335

European standard EN 335 describes how durable wood products can be used, and relates this to the NTR wood protection classes..

Use class EN 335

Use classService conditionsExampleRecommended wood protection class
UC 1Interior timbers in dry conditionsFurniture, interior claddingNot specified in NTR
UC 2Wood above ground and under cover and fully protected from the weather but where high environmental humidity can lead to occasional but not persistent wetting.Roof trusses, exterior timbers under coverNot specified in NTR
UC 3Wood above ground and either continually exposed to the weather or subject to frequent wetting; where there is relatively easy to replace damaged components and where the consequences of failure will be moderate.3.1 Windows and doors etc.

3.2 External cladding, decking, garden timbers
3.1 NTR B

3.2 NTR AB
UC 4Wood in contact with the ground or fresh water or severely exposed to the weather; or if wood component is inaccessible or where the consequences of failure will be particularly serious.4.1 Transmission poles

4.2 Railway sleepers, fence posts, bridges
4.1 NTR A pole

4.2 NTR A
UC 5Wood constructions in sea water and constructions subject to extreme conditions or where there are special durability and strength requirements. (Sea water. Salinity > 0,6%)Wharf timbers, jetties, pilesNTR M

good reasons for NTR certified wood

Leave the forest be!



Safe and effective!

Circular construction material!

Four times longer!