NTR means trust

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

NTR means wood you can trust

The Nordic Wood Preservation Council, the Swedish Wood Preserving Institute and research institutes and universities have all had a significant influence on the development of wood preservation standards in Europe and around the globe.

The wood protection classes according to the NTR-system are coordinated with the European standards EN 351-1 and EN 599, the established industry standard. However, the NTR system goes further by also specifying User Class and Penetration as well as several rules for achieving good durability and consistently good quality.

The NTR wood quality system also covers all wood materials and new technologies. With this, modified wood products such as chemical modified wood, heat-treated wood, silica-impregnated wood and linseed oil-impregnated wood can compete on equal terms. Customers and wood specifiers receive correct, factual and comparable documentation on the durability of wood products.

Wood that’s certified to last

For a producer of longer-lasting wood, it is easy to connect a new product or process to the NTR wood quality system. The cost of participating in NTR is a fraction of producers’ other development and marketing costs. The real challenge is to prove the new wood product is durable and is of robust quality for industrial manufacturing. The rigorous approval process consists of field tests lasting five years or more, which among other things assess the wood product’s resistance to rot. Products that pass the test earn the right to have the NTR label, which serves as a guarantee of a long service life, durability and quality.

The requirements for durability and quality are strict in The European EN standard’s, but the standard is even more exact in the NTR system. There, only products with improved durability pass the tests and receive the quality labelling rights. The wood protection classes in NTR’s wood quality system and the European standard are designed to provide a much better durability than untreated wood.

Responsible specifiers and buyers

The specifier / buyer has a key role in the quality process. They must be familiar with wood grades and durability classification in order to be able to independently verify product documents and test reports, especially if intending to buy something other than NTR-classified wood. Many non-NTR approved products present test certificates that don’t assess durability and service life. Demand relevant documentation! The NTR system helps the buyer make informed decisions.

“Products that pass the test earn the right to have the NTR label, which serves as a guarantee of a long service life, durability and quality.”

good reasons for NTR certified wood

Leave the forest be!



Safe and effective!

Circular construction material!

Four times longer!