Lumber, or sawn timber, is often the material of choice for construction because of its diversity of properties, and, if sustainably managed, is environmentally friendly. But international trade of lumber has its difficulties due to a lack of classification systems that are universal to all. And so the ISO technical committee on timber structures (ISO/TC 165), drawing on the input of experts from over 60 countries, for the most part in timber-producing and -consuming regions, developed a suite of International Standards that help reduce these barriers to trade by producing standardized frameworks and ways of working that can be used by everyone.

Why have an international lumber classification system?

“One of the challenges within the industry is that there are hundreds, if not thousands, of timber species-grade designations, each with unique engineering properties, so choosing the most appropriate for a construction project is not easy,” said Erol Karacabeyli, Chair of ISO/TC 165.

“To address this ever increasing problem, Europe introduced a lumber classification system that required all lumber species-grade combinations to be categorized into about ten classes. The European system, however, was not acceptable to the North American industry. But after years of work and negotiations, the committee was able to develop the framework for an international lumber classification system that is acceptable to all.”

What standards?

The standards developed by ISO/TC 165 are designed, therefore, to address grading and testing of both visually and mechanically graded lumber and provide a framework for an international strength classification system for both softwood and hardwood lumber. These include:

  • ISO 9709, Structural timber – Visual strength grading – Basic principles
  • ISO 12122-1, Timber structures – Determination of characteristic values – Part 1: Basic requirements
  • ISO 12122-2, Timber structures – Determination of characteristic values – Part 2: Sawn timber
  • ISO 13912, Structural timber – Machine strength grading – Basic principles
  • ISO 13910, Timber structures – Strength graded timber – Test methods for structural properties
  • ISO 16598, Timber structures – Structural classification for sawn timber
  • ISO 18100, Timber structures – Finger-jointed timber – Manufacturing and production requirements*

*Under development

Towards international adoption

The real benefit of the standards will be realized when all countries adopt them nationally, and it is anticipated that ISO 16598 for the structural classification of sawn timber will eventually be adopted globally, facilitating the trade of thousands of types of softwood and hardwood lumber.

Looking forward

ISO/TC 165 also has a number of projects in the pipeline, including International Standards and related documents for:

  • Cross-laminated timber (CLT)
  • Vibration design method for timber floors
  • Shear connections for timber-concrete slabs, a hybrid system that gives designers new choice
  • A framework for self-drilling screws
  • Long-term structural performance of wood-based products
  • Yield point for connections in timber structures  
  • Bamboo