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 class | Service conditions | Example | Recommended wood protection class |
|---|---|---|---|
| UC 1 | Interior timbers in dry conditions | Furniture, interior cladding | Not specified in NTR |
| UC 2 | Wood 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 cover | Not specified in NTR |
| UC 3 | Wood 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 4 | Wood 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 5 | Wood 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, piles | NTR M |
