Thermally treated wood is one that has undergone a heat treatment that alters some of its qualities. In essence, it consists of increase the temperature of the wood almost to the point of combustion, above 200 degrees. This process, which can take approximately 8 hours, not only requires total absence of oxygen, no chemicals are added.

Although this treatment can be applied to any wood species, the normal and logical thing is to do it in abundant wood to obtain some of the properties that the heat treatment provides and that the species in question does not have. Some of these species are: pine, spruce, poplar, birch, ash, beech, maple …

It is not a recently discovered process, it has been known for millennia that burning the surface of wood increases its durability. However, many wood professionals are unaware of this treatment, its advantages and possible disadvantages.

After burning the wood, the surface of the wood is prepared with a bristle brush and vegetable oil is applied. Wood treated in this way can reach a durability of 80 years. This technique in Japan, where it is common, is called Shou-sugi-ban.

Characteristics of heat treated wood

The heat treatment process causes changes in the internal structure of the wood. Many of these changes are desired, others are simply a side effect and some imply certain limitations in the use of wood.

  • The wood darkens and at the same time the color is homogenized, both in the sapwood and in the heartwood.
  • Resistance to fungi, insects and humidity increases exponentially. What improves its durability.
  • The new chemical composition of wood has some inferior mechanical properties. That is, it is less elastic and will break sooner if you flex it.
  • It loses density.
  • Harder surface.
  • Increase stability of wood and internal stresses are reduced. The swelling and shrinkage of the wood decrease (between 50% and 90%).
  • Drastic reduction of wood moisture.
  • Improves its thermal insulation properties.
  • It is lighter due to the change in its composition and the loss of moisture.
  • The wood resin itself is eliminated.
  • Thermal conductivity improves.
  • It does not require the application of additional chemicals for protection.
  • As for the price of heat-treated wood, it doesn’t have to be significantly higher.

The result is so different from untreated wood that we can speak of a new type of wood.

Main Uses

This treatment, among other things, improves the behavior of the wood against the weather, which is why most of these uses of heat-treated wood are external or subjected to humid environments.

  • Carpentry: doors, windows, friezes …
  • Outdoor furniture.
  • Outdoor floors or floors: gardens, swimming pools …
  • Wall or fa├žade coverings, both interior and exterior.
  • Saunas and bathrooms

Note: It is not advisable to use heat-treated wood as a structural element due to its mechanical deterioration.

Heat-treated wooden pallet

One of the uses where heat treated wood stands out is the manufacture of outdoor floors. The treatment, as already mentioned, improves the stability and durability of the wood, even without the application of chemicals.

In other words, the wood swells and contracts much less in the face of environmental changes, resistance to wood-eating insects and fungi, and there is also the possibility to change the tone, which is very interesting from an aesthetic point of view.

We can also say that it is a responsible and economical option. The manufacture of heat-treated wooden pallets does not generate waste and does not pollute beyond the energy used in the manufacturing process, the amount of energy being even less than that used in other processes or treatments.

In addition, it allows the use of abundant wood species (although initially not suitable for outdoors) at a lower price and to a certain extent avoiding overexploitation of tropical species.