National quality regimes and industry standards

Nordic Wood Preservation Council, NTR-mark

The NTR-system started in The Norden countries – Denmark, Finland, Norway and Sweden in 1960’s. It is now in use in The Baltics and Poland. The Nordic Wood Preservation Council’s classification, approval, and third party control scheme is guided by three main Documents.

108 companies from 9 countries hold certificates and a right to mark the products with the NTR mark. NTR-system is open to all producers in Europe and all types of preservatives or modifications methods as long as the wood product is durable and is possible to produce with robust quality.

Wood protection classes NTR A (UC4) and NTR AB (UC3.2) are most used following the EN 350 use class and other CEN standards.

You can find more information from


The three systems in Switzerland operate under “Lignum Gutezeichen”:

  • Poles only: Empa (Lignum-Gutezeichen ).
  • Other vacuum-pressure treated timber: (Lignum-Gutezeichen ).
  • Timber cladding: (Gutezeichen fur Fassadenschalungen in Holz), including surface treatment.

You can find more info by Lignum: Link (German and French)

United Kingdom

In the UK the Wood Protection Organisation (WPA) is a technical and advisory organisation specialising in the development and promotion of wood protection technology. The WPA acts as a principal technical advisor to the British Standards Institution in setting British standards relating to wood preservation, wood modification and fire protection.

The WPA operates the WPA Benchmark quality assurance and product approval scheme to help build buyer confidence in treated wood performance. For more information, please go to


The German quality scheme is operated by RAL quality assurance association (RAL-Gutegemeinschaft impragnierte Holzbauelemente c.V.) For more information, please go to


The dutch quality scheme is KOMO. It’s an accredited scheme and SKH is the Certifying Body. Part of the requirements is the declaration of appropriateness of the preservative meaning that on top of the legal approval by the Competent Authority a judgement is made on the effectiveness of the preservative.

  • KOMO (KOMO is a well-recognized quality mark in the building sector, but even in the DIY sector it is used.)
  • SKH (In the timber sector the most recognised CB.) The requirements for certification of treated timber, Requirements for preservatives, Requirements for modified timber.
  • The competent authority:
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