By Kim Murray

Builders, renovators, architects and interior designers are always looking for unique ways to stand out from the crowd.
Thermally Modified Wood (TMW) is one way to do that. It adds a unique and warm touch to wood. People love it for the way it looks, acts, and behaves as an environmentally friendly product.

But what is it, exactly?

Thermal modification is a process of drying, heating, cooling, and re-humidifying wood. It’s a technology carried out in a controlled atmosphere without adding any chemicals. The resulting change gives the wood better durability and performance.

The heating process improves the resistance to fungi degradation and improves stability. Since the colour of the wood deepens, any scratches can be eliminated with a quick sanding.

When thermally modified wood is exposed to UV rays, the “greying” of the wood is accelerated, and its mechanical resistance is reduced. So if it is to be used outside, it needs to be properly prepared (by sanding and cleaning) and then protected with oil, dye or varnish every two to three years. (Some TMW manufacturers offer pre-stained products.)

Because of its reduced mechanical resistance under UV rays, TMW shouldn’t be used for structural projects such as building framework.

But other than structural use, Thermally Modified Wood can be used in the same way as any other wood. It’s excellent for interior and exterior siding, flooring, and furniture. It’s also a good choice for moulding and door framing because of its greater dimensional stability.

TMW enhances the beauty and the value of natural wood. The heating process gives darker shades that are impregnated into the whole piece of wood. The higher the temperature, the darker the shade — just like coffee grains.

Though the heat treatment process can be done on all species of wood, the most common ones are softwoods such as pine and poplar, and hardwoods such as oak, maple and birch. At the moment, ash is the most popular species for TMW.

TMW adjusts itself to its environment, so precautions with installation are important. If you’re using TMW floorboards, for instance, make sure the wood acclimates to the room at least 24 hours before installation.

If you’re using TMW boards for exterior siding, you will need to keep a minimal clearance of 12 inches from ground level to avoid direct contact with water and snow, and to leave three quarters of an inch air space between the boards and the wall to keep good air circulation. It is also important to leave an eighth of an inch between rows to allow some expansion as the wood regains humidity.