About Co2 Thermo Timber

Co2 Thermo Timber
Co2 Thermo Timber (Thermowood®, heat treated timber) is produced by heating and mist spraying softwood in kilns of 200 degrees Celsius plus for up to 4 days.

This causes chemical and structural changes to occur within the timber. All the moisture and resin are effectively removed from the timber decreasing the likelihood of swelling and cracking compared to non heat treated timber making it a more stable product and longer lasting.

The heating process breaks down hemicellulose so the wood doesn’t contain the nutrients which allow rot and fungi to grow and develop. The process does not involve injecting or spraying any chemical on to the wood.

It is an environmentally friendly product and all our timber originates from well-managed FSC certified forests.

The colour of Thermowood is affected by the temperature the wood is subject to and the length of time it is exposed to the heat. There will be a slight variance in colour due to different softwood densities, but generally, the higher the temperature the wood is exposed to, the darker the Thermotimber.

Thermotimber Maintenance & Treatment

Thermotimber has a 30yr guarantee, because of its high durability it does not need a surface treatment applied to it. You may choose to add a finish, stain or paint to the timber to enrich its colour see our accessories page, but if it’s left untreated, the wood will naturally change to a silvery grey.

Excellent products for outdoor cladding


When selecting your timber type for your project it is worth taking in to consideration BS EN 350 timber durability class.

Durability is the ability of a species to resist decay either naturally or through preservatives. The Class is based on the ability of the heartwood (inner part of the tree) to resist fungal decay. The sapwood (the living outermost portion of the tree)is considered not durable and should not be used for external projects without preservative.

BS EN 350 has 5 classes of durability they are:-

Class 1 to 3 can be left as untreated timber, a natural ageing process will accrue e.g. Larch will turn a grey colour. Class 4 and 5 will need to be treated with preservatives.

For further information see www.greenspec.co.uk/building-design/cladding-durability-quality