Pros and Cons of Thermally Modified Wood

Thermally modified wood is a relatively new wood product, with modern thermal modification methods emerging in the 1990s. In just a few decades, thermally modified wood has made a substantial impact on all types of building and architectural projects. The advantages of working with thermally modified wood are numerous. But many people are still unfamiliar with the product and are unaware of what it has to offer. This is understandable, as it has been around for such a short period of time.

Thermally modified wood has several unique properties compared to other wood products. With that said, anybody who works with lumber should be careful in their consideration of what types of wood they use. 

To provide a better understanding of how and when to use thermally modified wood, here are some of its pros and cons.

Thermally Modified Wood vs. Pressure Treated Wood

First, it would help to briefly explain what sets thermally modified wood apart from other types of wood. Treating wood is not a new concept at all, nor is the idea of using heat to modify wood. Another common type of treated wood is pressure treated lumber. It can be easy to mix these two types of wood up, as they share many qualities. However, the treatment process is different.

As the name implies, pressure treated wood uses pressure induced by a vacuum to insert chemical preservatives into the wood. Thermally modified wood, on the other hand, uses heat to alter the wood’s composition.

The modern thermal modification process uses a specialized low-oxygen kiln to prevent combustion at high temperatures. This process removes certain natural compounds from the wood which attract insects and fungi. As a result, thermally modified wood is better protected against these common threats. The thermal modification process also makes wood less absorbent, meaning it has more protection against water damage.

Pros of Thermally Modified Wood over Pressure Treated Lumber

Dimensional Stability

When wood is described as “dimensionally stable,” it means that it’s not prone to warping or cupping. These phenomena are especially common in wooden boards that have suffered water damage.

Due to the unique thermal modification treatment, thermally modified wood has a lower moisture content than most wood materials. As a result, thermally modified wood absorbs less water when exposed to moisture. This means it is less susceptible to water damage over time, making it a very dimensionally stable wood material.


In addition to its dimensional stability, thermally modified wood is also resistant to the most common sources of wood deterioration. As mentioned, the thermal modification process removes natural compounds that are common food sources for termites, mold, and fungus. Each of these organisms can cause significant damage to wood, very quickly.  When lumber undergoes thermal modification, its expected lifespan increases by several years simply because it is protected from these threats.


By becoming more durable, thermally modified wood is also more sustainable than other wood products. Most thermally modified wood products are expected to last at least 25 years, and often longer. This means fewer resources are needed to replenish homes and buildings that use thermally modified wood. Wood on its own is already a highly sustainable building material. So, enhancing its sustainability is adding to what is already a notable strength for wood products in general.


One of the biggest advantages that thermally modified wood has over pressure treated lumber is that it does not rely on chemicals. The chemicals used in other forms of wood treatment can be potentially harmful in some cases. Thermally modified wood, on the other hand, uses no chemicals at all. The wood’s composition is modified using high temperatures and nothing else. This means there is no adverse environmental impact when thermally modified wood is created or used in building projects.

Unique Color

In addition to its practical benefits, thermally modified wood also offers aesthetic advantages according to prominent builders and architects. The thermal modification process gives the wood a darker hue. This can create a very distinct and rich look for thermally modified wood siding, decking, and other fixtures. When choosing wood products, functionality is not always the only factor under consideration. Design elements are also a priority for many builders and homeowners. Thermally modified wood adds an intriguing visual element, in addition to its functional advantages.

Cons of Thermally Modified Wood

More Expensive Than Untreated Wood

The most notable drawback of using thermally modified wood is that it costs more than untreated wood. This is because the thermal modification process requires time and resources. However, considering thermally modified wood should last longer, the increased price often evens out in the long run. It may cost more, but thermally modified wood is a premium lumber product, and is still available at affordable rates.

Can Become Brittle Over Time

The heat treatment which thermally modified wood undergoes changes the texture of the wood. While this process makes it more resistant to some types of damage, it also leaves it more prone to chipping or splintering. It usually takes several years for these effects to be seen. However, this is the most common complaint that people have about thermally modified wood.

More Flammable

The low moisture content of thermally modified wood unfortunately means it will burn more quickly if exposed to fire. This does not mean that it should catch fire more easily than other types of wood. But, in the event that a fire does occur, thermally modified wood will struggle to withstand the flames.

Where to Use Thermally Modified Wood

Last, you may be wondering what the best uses for thermally modified wood are. Thermally modified wood is versatile and can be used for any type of wood project. However, its ability to resist water, mold, and insect damage makes it particularly well-suited for outdoor projects. Thermally modified wood siding and thermally modified wood decking, for instance, are two extremely popular options for builders and homeowners.

To explore a wide range of world-class lumber products for your next wood project, browse Lumber Plus’ range of hardwood and composite decking materials.

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