The Nordic Wood Preservation Council (NWPC) publishes an industry standard for wood protection classes that is in line with the European standard for ranking and assessing the durability of wood products and its treatment or modification.

Over the years, the Nordic Wood Preservation Council and the Swedish Wood Preserving Institute, together with research institutes and universities have had a significant influence on the development of standards in the field of wood preservation in Europe as well as globally.

The wood protection classes according to the NTR-system are coordinated with the European standards EN 351-1 and EN 599 which is an established industry standard. However, the NTR-system goes several steps further by specifying User Class and Penetration as well as a number of very concrete rules to achieve good durability and high, consistent quality.

Responsible specifiers and buyers

The customer / buyer must take their responsibility as they have a key role and must be familiar with wood grades and durability classification in order to be able to independently verify product documents and test reports if you intend to choose something other than NTR-classified wood. Many non-NTR approved products present test certificates that are irrelevant to assess durability and economic life. Demand relevant documentation! The NTR system helps the buyer make fact-based decisions.

TFor a producer of durability modified wood, it is easy to connect a new product or process to the NTR wood quality system and the cost of participating is relatively small in comparison to the producers other costs for development and marketing. The real challenge is to prove the new wood product is durable and has a robust quality in industrial manufacturing. The rigorous approval tests take up to 5 years to carry out in field tests and trials to assess a wood products resistance to rot and more. Products that have passed the test have the right to label the product with NTR-mark.

The NTR wood quality system

The requirements for durability and quality are strict in the EN standard and even more strict in the NTR system, which means that only products with improved durability pass the tests and receive labelling rights in accordance with the NTR system. The wood protection classes in NTR wood quality system and the European standard are designed to provide a significantly improved durability compared to untreated wood.

The customer / buyer must take their responsibility as they have a key role and must be familiar with wood grades and durability classification in order to be able to independently verify product documents and test reports if you intend to choose something other than NTR-classified wood. Many non-NTR approved products present test certificates that are irrelevant to assess durability and economic life. Demand relevant documentation! The NTR system helps the buyer make fact-based decisions.

The most common wood protection classes for consumers and construction are NTR A, NTR AB and NTR Gran.

The NTR wood quality system

The requirements for durability and quality are strict in the EN standard and even more strict in the NTR system, which means that only products with improved durability pass the tests and receive labelling rights in accordance with the NTR system. The wood protection classes in NTR wood quality system and the European standard are designed to provide a significantly improved durability compared to untreated wood.

The customer / buyer must take their responsibility as they have a key role and must be familiar with wood grades and durability classification in order to be able to independently verify product documents and test reports if you intend to choose something other than NTR-classified wood. Many non-NTR approved products present test certificates that are irrelevant to assess durability and economic life. Demand relevant documentation! The NTR system helps the buyer make fact-based decisions.

The most common wood protection classes for consumers and construction are NTR A, NTR AB and NTR Gran.