When looking to the future, we hope to see a world where sustainability is at the forefront of products, businesses and general life. As a result, the demand for sustainable and eco-friendly building materials has dramatically increased over recent years. Society is becoming more aware of the impact that our go-to building materials can have on the environment, therefore seeking alternatives which remain durable and functional, whilst also reducing the environmental impact. This is where thermo-timber comes in. It’s great for those who wish to build with hardwoods that are sustainable, durable and affordable, thus quickly becoming more popular.

What is Thermo-timber?

Let’s start at the beginning. Firstly, thermo-timber is a wood material that has been modified using heat and steam to improve its durability, stability and moisture resistance. The beauty of thermo treatment is that it involves no chemicals. The process was invented by Harry Tiemann in 1915, and in 2007 the process became commercial.

What is the process of thermo-treating timber?

The process of thermo-treatment requires pre-drying wood to reduce it’s moisture content to around 8-12%. Next, it is placed in a thermal modification chamber to be heated between 190°C and 240°C for several hours, depending on the wood species and desired outcome. After, steaming then takes place during this part of the process, creating a reaction which changes the physical and chemical properties of the wood. It alters the cellulose and hemicellulose molecule structures, in turn, affecting the valency. As a result, this stops attracting water molecules binding onto the helix. After the heat treatment, the wood is allowed to cool slowly in the chamber, which helps to minimise stress and cracking.

In the UK, we have one thermo-treating plant up and running, still in its infancy, but showing good results. The remainder is currently imported from the EU.

What does thermo-treating timber do?

The heating process changes the wood’s structure by removing moisture and other volatile compounds. The result? A more stable and durable material ideal for both interior and exterior projects. It also makes the timber unpalatable to insects, as well as fungi infestation.

Why is Thermo-timber the future of British hardwoods?

It’s sustainable

At the top of our list: thermo-timber is sustainable! As the process of thermo-treating only involves heat and steam, it means that it is a green and eco-friendly option when comparing with other chemically treated timbers. In addition, thermo-timber comes from sustainably managed forests. This means the wood is harvested in a way that ensures that the forest remains healthy and productive for future use. To read more about sustainably-managed forests and timber, read our recent blog post: How does sustainable timber support climate change.

Durability is increased

Once the timber has been subject to thermo-treatment, the wood is less susceptible to decay, rot and insect damage than untreated timber, meaning it is long-lasting and can withstand extreme weather and maintain it’s structural integrity over time. This has been evident from durability accelerated testing, it has been suggested that the timber can withstand the elements for over 25 years, and in some situations, over 50 years. This makes it a better investment for homeowners and businesses who want to avoid costly repairs and replacements further down the line. As a result, it’s ideal for outdoor projects such as decking, cladding, porches and fencing.

The timber’s stability is more robust

So, we already know that thermo-timber is more durable than untreated wood, but it doesn’t stop there. It’s also more stable than other untreated woods. Once the moisture is removed from the wood, it reduces its tendency to warm, twist and split. As a result, this makes thermo-timber a much better option for construction use where stability and dimensional accuracy are crucial, such as wooden flooring and panelling.

It’s appealing

Construction materials need to be durable, and ideally sustainable. However, if they don’t look good, then they won’t be fit for the job! Thermo-timber is often favoured as it has an attractive appearance. In the thermo-process, the wood darkens to reveal a rich, warm, tobacco-brown colour. Uniformity is also evident in the final product, as well as a natural, textured look. This is because the wood grain becomes more pronounced, making it ideal for interior projects such as flooring and panelling.

It doesn’t break the bank

You’d have thought a material with so many advantages comes with a hefty price tag, but that couldn’t be further from the truth as it’s actually an affordable option. Naturally, the capital cost put into a commercial plant is very expensive, as well as the energy required to get the steam heated to such a high temperature, the outcome allows wood that isn’t usually suitable for outdoor use, appropriate for external projects. It may cost more than the original product, but it is more durable than untreated wood. Therefore, it requires less maintenance over time, resulting in significant cost savings. Additionally, because it comes from sustainably managed forests, it is a cost-effective and ethical choice.

What timbers can be thermo-modified?

Thermo-treatment can be applied to a variety of wood species, but the degree of modification can vary depending on the species and the specific thermo-treatment process used. Some of the most commonly thermo-treated timbers include: Douglas Fir, Ash, Oak Radiata Pine poplar, Alder beech (although less easy to process) and Spruce. Density plays a big part in the outcome.

Ayous, for example, has been thermo treated to 80mm thick! To explore some of the timbers we stock and a description of them, please head to Timber Supplies.

The UK has only two durable hardwoods commercially available, Oak and Chestnut. The latter is becoming more difficult and rarer to source in ideal diameters and continuity of stock. These two timbers lend themselves to external applications due to the tannin in the timber which is a natural preservative.

To conclude, thermo-timber is becoming increasingly popular for those who want to build with sustainable, durable, and affordable hardwoods. Its eco-friendly production process, durability, stability, attractive appearance, and affordability make it an ideal choice for a variety of construction applications. As people become more aware of the impact that traditional building materials have on the environment, thermo-timber is likely to become a more popular choice for those who want to build sustainably. If you want to explore thermo-modified timber, don’t hesitate to contact us and one of our expert team will be in touch.

WL West Timber is a family-owned sawmill & timber merchant in West Sussex with over 155 years’ industry experience. We provide a wide range of air-dried oak and kiln-dried oak timber products and supplies. We also build and install custom projects for our customers.

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