Thermal modification

Thermo modification is a computer-controlled process which is carried out in special kilns at high temperatures. Only steam and heat are used with no chemicals added.

The advantages of thermally modified wood are:

  • 100 % natural treatment – only high temperature and steam is used in process.
  • Wood is treated fully, not only near surface like with chemicals impregnated wood
  • Resin free
  • For all climates
  • Increased wood dimensional stability and durability
  • Decreased water absorption
  • Less deformations and tensions caused by humidity changes
  • Environmentally friendly and fully recyclable
  • Beautiful wood, rich in color.

According to the European Standard EN350: 2016, wood species are classified into five durability classes:

DurabilityDurability class 1
Very durable
Durability class 2
Durability class 3
Moderately Durable
Durability class 4
Slightly durable
Durability class 5
Not durable
Durability periodOver 25 years15 – 25 years10-15 years5-10 yearsUp to 5 years
Wood speciesThermo Ash
Thermo Pine
Thermo Ayous
Thermo Spruce
European Oak
Thermo Pine
Thermo Ayous
Scots Pine
Red Oak

Wood thermal modification involves heating wood material to a temperature of 180–220 °C while at the same time protecting it with steam.

The steam protects the wood, but it also influences the chemical changes taking place in wood.

100% natural and non toxic – only heat and steam are used in the manufacturing process and no chemicals are added.

Thermally modified wood is an environmentally friendly and fully recyclable product, the manufacture of which does not include any harmful chemicals.

Unlike chemical impregnation, thermal modification enhances the wood through and through, not just the outer surface. The result is boards that are durable and stable in every sense.

Lowered equilibrium moisture content of thermally modified wood makes it dimensionally stable and the material retains its shape far better than untreated wood. After thermal modification, the moisture content of the wood decreases to around 4-6 percent. As a result of this lowered equilibrium moisture content, thermally modified wood does not react to changes in humidity as drastically as untreated wood.

The dimensional stability of wood due to varying air humidity clearly decreases in thermally modified products.

This is due to the reduction of wood shrinkage, lower equilibrium moisture content and slower absorption of humidity because of heat treatment.
The seasons change – better than corresponding untreated or chemically treated wood. It can be used inside or outdoors, in any climate.

Thermally modified wood is a good sustainable alternative to tropical hardwoods.