Structural timber testing

Test strength, stiffness & performance of structural timber to BS EN 408 and BS EN 338.


Independent testing for structural timber products to BS EN 408 and BS EN 338 for strength, stiffness, shear and bending for strength and performance.

We offer independent and UKAS-accredited testing to EN 408 for structural timber products. We also provide testing for the classification of structural performance in relation to EN 338 for strength graded timber, including:

  • bending strength
  • bending stiffness (modulus of elasticity)
  • shear strength
  • bearing strength
  • compression strength
  • moisture content and density

As with all established structural products, the performance characteristics of strength graded timber are verified on the basis of existing test standards. Strength graded timber is considered as a structural product as it can be CE marked.

The structural performance of strength graded timber is a measure of how the timber will contribute to the mechanical stability of a building typically as part of a floor, wall or roof system.

Strength graded timber is assigned to a strength class which contains a range of characteristics that are required by structural engineers. The most commonly available strength classes in the UK are C16 and C24 while TR26 is used for trussed rafters. Strength graded timber is used as framing and carcassing for floor joists, wall studs, columns, cut roofs and trussed rafters.

Initial type testing (ITT)
Initial type testing (ITT) to assign a timber species to a strength class for the first time requires a sizeable test programme. It is more common to commission a smaller test programme to verify that a strength grading machine has been installed and set up correctly as part of a certification process. We can also develop bespoke testing programmes for new and innovative products.

The tests for structural timber use specimens that are similar in size to timbers used in practice. The tests are carried out on representative samples of graded timber as manufactured for end use. The results obtained from such tests are analysed to determine the characteristic capacities required to design in accordance with the European Design Code for timber (EC5). In the past, permissible safe values were derived, appropriate for designing in accordance with the UK structural design code BS 5268 (now withdrawn).
European structural timber testing
European structural timber testing includes the following:
  • BS EN 408 - Timber structures. Structural timber and glued laminated timber. Determination of some physical and mechanical properties
  • BS EN 384 - Determination of characteristic values of mechanical properties and density
  • ISO 3131 - Determination of density for physical and mechanical tests
  • BS EN ISO 12750 - Determination of moisture content by drying at elevated temperature
  • BS EN 13183 - Moisture content of a piece of sawn timber. Determination by oven dry method
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