Thermo Wood

ThermoWood is timber modified through a controlled thermal process at temperatures of approximately 160–215 °C in an oxygen-free environment, without the use of chemicals. The treatment reduces moisture content and breaks down part of the hemicelluloses, which substantially improves the material’s dimensional stability. The wood becomes more resistant to rot, mould and biological pests. It also gains a darker, even tone throughout the entire profile, not only on the surface. In saunas, hot tubs and outdoor pergolas, it is used for its ability to withstand moisture and temperature fluctuations. This is not an impregnation — the properties change structurally.

Advantages of Thermo Wood

• High dimensional stability: Lower water absorption means less warping, cracking and deformation in high-humidity environments.
• Longer service life without chemical impregnation: The material is naturally more resistant to biological decay, which is essential for outdoor wellness projects.
• Lower maintenance costs: No need for regular chemical pest protection. Routine surface maintenance is sufficient, depending on the desired appearance.
• Aesthetic value without additional staining: The darker tone results from the thermal process, not from a coating, so the colour stays consistent even if scratched.

ThermoWood and ordinary timber: what the difference is

In Slovak, ThermoWood is commonly called termodrevo. It is the same material – timber whose properties have been changed by heat, not by chemical impregnation. The table below summarises how ThermoWood differs from untreated and from pressure-impregnated timber in outdoor use.

ThermoWood cladding and decking: where it is used

In outdoor wellness setups, ThermoWood is used for three distinct jobs. As ThermoWood cladding on the facade of a sauna or of the technical housing, where dimensional stability matters as rain and sun alternate. As the shell of a bathing tub, where the timber is in permanent contact with moisture. And as the structural beams of a pergola, where a strength requirement is added.

Inside a sauna, ThermoWood has a different role from the timbers used for benches. It suits wall and ceiling cladding thanks to its low moisture absorption, while for contact surfaces the timbers chosen are those with the lowest thermal conductivity.

Related terms: Siberian larch, Pine cladding, Abachi, Western Red Cedar.