Thermowood Siding & Decking

Genuine Wood Sourced from Renewable,
Certified Nordic Forests.

100% Chemical-Free Modification Process.

Thermowood is a Finnish innovation and a global phenomenon, a testament to its versatility and potential. Thermowood’s siding and decking represent an innovative approach to traditional wood cladding by enhancing wood’s durability and dimensional stability through a heat treatment process. This environmentally friendly process involves heating wood to high temperatures in a controlled environment, which fundamentally alters the wood’s chemical and physical properties. The result is a highly resistant material to decay, moisture, and fungal growth without chemical preservatives. Thermowood retains the natural beauty and grain of wood with increased longevity and lower maintenance requirements. Its rich, dark tone and smooth finish add a sophisticated aesthetic to any building’s exterior, making it a popular choice for those seeking sustainability and style in their construction projects. 

Thermowood decking and siding products are versatile and suitable for facades, interiors, and landscaping across diverse climatic conditions.

Heat & Steam Process

Thermowood is a unique wood material renowned for its exceptional properties, achieved through a meticulous heat and steaming process. This innovative technique involves subjecting the wood to high temperatures and steam in a controlled environment, altering its cellular structure, and enhancing its physical characteristics. As a result, Thermowood exhibits remarkable dimensional stability, increased resistance to weather elements, and improved durability without the need for chemical treatments. The process effectively removes moisture from the wood, reducing its propensity to shrink, warp, or crack, even under challenging environmental conditions. Thermowood’s thermal modification also imparts a beautiful, rich color to the wood, adding to its aesthetic appeal. Overall, the heat and steaming process behind Thermowood exemplifies a harmonious fusion of science and craftsmanship, producing a material that excels in functionality and beauty, instilling confidence in its performance.

More on the Thermal Modification process:

The Thermal Modification process enhances wood’s properties thoroughly. Within the thermal modification chamber, the temperature gradually rises to 212°C, a process that can extend up to 110 hours. Water plays a crucial role in two ways: it prevents the wood from burning during treatment due to high temperatures and ensures the final product’s high quality. Towards the end of the process, moisture is reintroduced into the chamber to prevent cracking and promote the product’s longevity. Upon completion, the wood’s moisture content typically ranges from 4 to 7%, resulting in Thermowood products that are exceptionally stable and durable.

Environmental Responsibility

Thermowood is not just about beauty and functionality. It’s about responsibility, and by choosing it, you’re making a sustainable choice. This material embodies VANTIA’s commitment to environmental stewardship. Thermowood’s dedication to sustainable forestry ensures that wood is sourced from responsibly managed forests, promoting biodiversity and long-term forest health. And the thermal modification process? It enhances the wood’s durability and weather resistance and extends its lifespan, contributing to a more circular economy by reducing waste. Thermowood’s transparent approach to sustainability, as evidenced by its adherence to various certifications and standards, underscores its unwavering dedication to creating products that are not only beautiful and functional but also environmentally sound.


Product quality begins in the Nordic forest, where Thermowood sources renewable pine and spruce. These trees thrive in challenging climates, growing slowly and developing strength ideal for our purposes. We ensure the integrity of our raw materials through certified chain-of-custody management, independently assessed and monitored.

A proprietary method patented for crafting Thermowood ensures non-toxic production. An independent third party oversees rigorous quality checks, guaranteeing an extended lifespan.

Dimensional Stability

Thermowood planks offer significantly enhanced dimensional stability compared to untreated wood, maintaining the original shape more effectively over time.
Thermowood’s lower equilibrium moisture content makes it dimensionally stable, and the material retains its shape far better than untreated wood. This outstanding stability allows Thermowood to be successfully used in all climates, including hot and humid weather conditions indoors and outdoors.

Natural Color Change

One of the many benefits of using Thermowood is its low maintenance. Over time, it naturally develops a beautiful silver color, a unique characteristic that sets it apart from other materials. This natural color change adds to its aesthetic appeal and eliminates the need for surface treatment, making it a cost-effective and time-saving choice for any climate.

Thermowood Siding and DeckingFAQs:

What surface coatings can I use with Thermowood?
Thermowood welcomes a wide range of high-quality proprietary surface coatings compatible with untreated wood. Tinted or pigmented wood oil, wax, wood-preserving stain, varnish, or paint containing a UV filter are suitable for treating Thermowood to maintain its surface color. This treatment can be applied thinly either before or directly after installation.
What is Thermowood maintenance like?
Thermowood boasts durability, needing no maintenance to endure the test of time. However, regular maintenance is advisable to preserve its original appearance and prevent minor cracks and splits. Renewing the surface treatment when needed is crucial. The frequency of re-treatment depends on factors like climate, usage, and UV exposure. To rejuvenate the surface entirely, washing discolored timber, ensuring thorough drying, and recoating are possible. Careful application of water pressure is necessary to remove discoloration without raising the timber grain.
What is Thermowood’s fire rating?
Thermowood boasts a D4 rating, equivalent to natural timber. Like unmodified timber, it readily accommodates standard fire retardant treatments.

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