Ever since it was introduced in Eastern Canada, thermally-modified wood (also called thermo-treated, thermally-treated and thermo-modified wood) has aroused a lot of interest, with its rich, warm stains. But beyond its attractive colouring, TMW has both advantages and limitations that must be taken into consideration from the very design stages. The main advantages of TMW may be summarized as follows: improved dimensional stability, increased resistance to fungal degradation and new, attractive colours. However, just like natural wood, untreated TMW tends to go gray when subject to inclement weather. And since it is slightly more breakable, its use for building structures is not recommended.
Canadian TMW producers use various technologies to treat the wood of a variety of species, both hardwood and softwood. However, since no standards have yet to be approved for the industry as a whole, the properties of tree species treated at high temperatures may differ from one manufacturer to another. In Eastern Canada, the manufacturers are collaborating with FPInnovations, cecobois and the Quebec Forest Industry Council (QFIQ) in order to set up a TMW classification standard based on four major categories according to their resistance to fungal degradation, their dimensional stability and the various colour grades. As a rule, the higher the temperature during treatment, the better the resistance to fungal degradation of a tree species, the greater the dimensional stability and the darker the colour. Thanks to this classification standard, consumers will be able to make a well-informed choice based on the use they want to make of the product (interior or exterior application).
Along with setting the classification standard, a quality control program will be implemented with an external audit in order, for example, to guarantee the repetition of in-plant treatments. FPInnovations is directly involved in this work as well, in cooperation with the QFIQ. The work on the classification standard and the quality control program is being carried out with the financial support of the National Research Council Canada and Formabois.
For more information on the research being conducted on thermally-modified wood, please contact Carl Tremblay, Scientist, Appearance Wood Products.