What is thermowood - Johnsons 12 April 2019

You may have heard of heat-treated timber its proper name is called thermowood. Thermowood is a sustainable material under the timber category, which is produced by the use of heat treatment that is also chemical-free

How is it produced?

It is made with the use of Scandinavian Softwood. The softwood is heated in a chamber kilns for up to 96 hours, with the temperature anywhere between 180 to 230 degrees. By using steam as a protective gas, it is a key part in helping stop the wood from splitting or getting damaged.

Thermowood’s Characteristics & Qualities

When the above process is happening, it causes the chemicals and the structural features to change within the timber. This then causes some of the qualities and characteristics to change. Most of the qualities and characteristics that help make thermowood cladding comes from the Scandinavian Softwood timber that has been heat treated. When Thermowood is made it is put through pressure and heat, also nitrogen and water vapour to control the drying process. Whilst all this treatment is happening it is carefully watched and can take from 24 hours to 96 hours. The timber is subjected to temperatures from 180 to anything up to 230 degrees. It all depends on the species.

When the wood is made to go through intensive heat, it dries out all the way into the core and all moisture is removed. Lower moisture means higher weather resistance, that means that thermally treated would can be used for exterior cladding, facades and other outdoor purposes

Dimensionally Stable

Because of the heat that the wood is exposed to during the production, it dries out deep into the core. This makes all the moisture and resin to remove from the timber. Therefore, thermowood doesn’t response to change of humidity as bad as untreated wood, which allows it to retain it shape better and the risk of cracking, shrinkage and the risk of swelling is lowered. Also, the wood doesn’t ooze resin or sap in high temperatures.

Environmentally Friendly

The wood which is used to make thermowood comes from well looked after, PEFC certified forest. Also, no foreign substances are used and no chemicals are used in any of the production. Thermowood is eco friendly material made by natural ways. The way thermowood is created by using heat and water vapour. This way is great for the environment, compared to other chemically treated wood.

Resistance to rot and fungi

Because of the heating process the wood goes through It breaks down hemicellulose, the wood therefore doesn’t contain any nutrients that let rotting and fungi to grow.

Increased longevity

All, if not most wood has and average life span, but when wood is treated with wood its average life span is made longer. However, it will depend on how high of a temperature is open to. Generally, it the higher the temperature, the longer the life spam.

Improved insulation

When wood is treated by heat is becomes more porous than what wood that hasn’t been treated, this then improves the insulating factors.


Thermowood can be thrown away or recycled when its not longer wanted or needed. If it is recycled it is recycled as untreated wood.

What can thermowood be used for?

When wood is put through the heat treatment, it makes the wood better. Because of this it extends what the wood can be used for. It enables the wood to be used for inside and out.

External uses

With its high resistance to decay it is great for exterior things. Some which include: decking, louvre blade and brise soleil

Get in touch...

If you would like to get a quote or find out more about our timber products that we offer please get in touch with us through our contact form, by phone or by email - we will be more than happy to help you in whatever way we can.

Call us: 0121 706 0404