Thermally modified timber

What are the disadvantages of thermally modified timber?

Depending on the duration and temperature of the heat treatment, the timber becomes less elastic and has a lower bending strength. It becomes increasingly brittle and can only be employed to a very limited extent in load-bearing structural usage. If you wish to use thermally modified timber in situations where structural performance is necessary, the suitability of the timber must first be tested on a case-by-case basis by a structural engineer.

Are there any other factors I need to consider?

Thermally modified timber tends to lighten in colour or become grey on exposure to sunlight faster than wood in its natural state. If you wish the wood to take on a grey, weathered appearance or do not mind this happening, the surface of the wood does not have to be treated in any way. Usually, the colour of the wood changes relatively evenly. However, to prevent dirt from permeating wooden floors, we recommend that you treat the surface, for example, with oil. If you wish to retain the colour of the thermally modified timber, you will need to treat the surface with a UV-protective preservative, and repeat the procedure at regular intervals.

Uses of thermally modified timber

As a rule, all species of European wood can be thermally modified.

In practice, however, the following species are generally used:

Species Examples of use
Birch Flooring/parquet, furniture, stairs
Beech Flooring/parquet, patio, decking, furniture, stairs, glulam products
Oak Flooring/parquet, furniture, stairs, patio decking, exterior cladding
Alder Planed wood for sauna construction, furniture
Ash Flooring/parquet, patio decking, furniture, stairs, exterior cladding, garden furniture
Spruce, pine Exterior cladding, patio decking, garden furniture, fencing, flooring/parquet, and more


Working with thermally modified timber

As a rule, thermally modified timber can be processed very well. However, its increased brittleness must be taken into consideration, because the wood can split or crack if it is not handled correctly. Furthermore, a very good dust extraction system is required because the dust particles generated from sanding and sawing are very small.

If you want to use screws in thermally modified timber, the you must always pre-drill the holes (due to the danger of cracking) and ensure that the screws are placed a sufficient distance from the ends to prevent splitting.

Thermally modified timber can also be glued. For precise instructions about how to glue it, you should contact the relevant adhesive manufacturer.