Developed in Finland during the 1990s, the ThermoWood® process is a patented method that subjects timber to high temperatures ranging from 180°C to 230°C in a controlled steam environment. This treatment modifies the wood’s chemical and physical structure, enhancing its durability, stability, and resistance to decay. The process is meticulously standardised, ensuring consistent quality across all batches.
With a Durability Class 2, it is comparable to Oak, and has a 15+ year lifespan when used externally above ground level.
Through exposure to heat and steam in an oxygen-free environment, the chemical composition of the wood changes.
During the process, the hemicellulose, a complex branched structure composed of sugar monomers found in cell walls, breaks down. The process alters the lignin and cellulose structures, improving the timber’s resistance to decay, enhancing durability, and increasing dimensional stability.
Thermowood is pine that has been carefully heat treated using only high temperatures and steam. No chemical preservatives. No artificial stabilisers. Just a controlled process that changes the cellular structure of the wood itself.
Thermal modification reduces the timber’s tendency to expand and contract with changes in temperature and humidity, helping it stay straight and true over time.
By removing excess moisture and altering the wood’s internal structure, the boards are far less likely to bow, cup or distort after installation.
The heat treatment makes the timber less absorbent, which limits fungal growth and significantly improves its durability outdoors.
The process uses only heat and steam, meaning there are no chemical preservatives, making it a reassuring choice for family gardens, schools and spaces used by children and pets.
Pressure treated timber is infused with chemical preservatives to slow down rot and insect attack. It is widely used because it is affordable and readily available, but it can be prone to movement, twisting and surface cracking over time.
Thermowood, on the other hand, is modified using only heat and steam. The process alters the wood’s cellular structure, reducing moisture absorption and improving stability without introducing chemicals. The result is a more dimensionally stable, natural timber that ages more gracefully and is better suited to premium applications.
For fencing, the difference is often seen in how straight and consistent the boards remain over the years.
When properly installed and well ventilated, Thermowood can last several decades outdoors. The exact lifespan will depend on exposure levels and maintenance, but it is significantly more durable than untreated softwood and more stable than many standard treated timbers.
Like all timber, good installation matters. Keeping boards clear of standing water and ensuring proper airflow will maximise longevity. At Taiga, we also pair our panels with Accoya posts and gravel boards to ensure the structure beneath the fence is just as durable as the panels themselves.
Yes, provided it is designed and built correctly.
Although Thermowood is often used for cladding, its stability and reduced moisture movement make it particularly well suited to fencing. A fence is constantly exposed to changing weather conditions, and timber that resists swelling and twisting will maintain a cleaner, straighter appearance for longer.
For those seeking a natural, sustainable and chemical free fencing option, Thermowood offers a balance of performance and aesthetic quality that traditional treated timber cannot easily match.
Yes. Like most untreated timber, Thermowood will gradually weather to a soft silver-grey if left untreated. This is purely cosmetic and does not affect its durability. If you prefer to retain the original warm tone, it can be maintained with UV-protective oils.
Yes! Although Thermowood fences are generally more expensive upfront, the increased stability, durability and reduced need for replacement often make it more cost effective over the long term. It is definitely a premium solution rather than a budget one.
It depends what you value most, but in many cases Thermowood offers a more stable and consistent solution for modern fencing.
Western red cedar has long been used for fencing because it contains natural oils that help resist decay and insect attack. It is lightweight, attractive and relatively durable. However, cedar can still move with changes in moisture, and quality can vary depending on grade and sourcing. It is also typically imported, which has environmental implications.
Thermowood begins as sustainably sourced pine that is heat treated using only steam and high temperatures. The process reduces the timber’s ability to absorb moisture, making it more dimensionally stable and less prone to twisting or cupping. The colour is rich and even throughout, and it weathers to a soft silver tone if left untreated.
