Thermally Modified Timber
Timber made durable through heat treatment.
Thermally modified timber is produced by treating wood with hot steam at up to 250 °C under controlled conditions. The swelling and shrinking behaviour is reduced by up to 70 %, the wood becomes more dimensionally stable, more durable (class 1–2) and acquires a uniformly dark colour. Thermo-oak and thermo-ash are popular variants for stair treads — as a sustainable alternative to tropical hardwoods, without chemical additives.