Natural durability of wood

There is a European standard that defines durability of wood and how to test, classify wood and wood products according their natural durability to biological agents.

The European standard EN 350 evaluates and lists the durability properties of all types of wood. The standard applies to solid wood and only heartwood 100%. Sapwood is never durable for any species. This is very important to know and it is also equal important how much or the wood is sapwood and heartwood. Some species is made up of only heartwood and some is only sapwood. This will make a huge impact on the durability of the woodproduct in use.   

The durability is stated on a scale from 1 to 5 where 1 is very durable and 5 is non-durable. Furthermore, there is information on variability and how much of it normally consists of heartwood and sapwood, respectively.


Wood spies type
Durability class
 Type of wood
Larch (origin Europe and Japan) 4 Conifers
Pine (European origin) (sylvestris) 3-4 Conifers
Douglas fir (native to North America) 3 Conifers
Douglas fir (grown in Europe) 3-4 Conifers
Yew (origin Europe) 2 Broadleaf
Birch (origin Europe) 5 Broadleaf
Ash (origin Europe) 5 Broadleaf
Oak (origin Europe) 2-4 Broadleaf
Teak (origin Asia) 1 Broadleaf
Teak (grown Asia etc.) 1-3 Broadleaf


When intervals are stated, such as on Pine and on Oak, it means that there are large deviations depending on, for example, plant location etc.

The standard is available for purchase from where standards is published and sold.

good reasons for NTR certified wood

Leave the forest be!



Safe and effective!

Circular construction material!

Four times longer!