Why thermowood is the best material for decking?

What makes thermowood so special?

Thermally modified wood stands out from traditional decking materials because it undergoes a specialized heat and steam treatment. This process changes the wood at a cellular level by removing sugars and moisture that typically attract decay, fungi, and insects. As a result, thermally modified wood becomes significantly more durable and stable, with improved resistance to rot, moisture, and warping.

Unlike pressure-treated wood, thermally modified wood is produced without chemicals making it a safe and environmentally friendly choice. The process also deepens the wood’s natural color, giving it a rich, attractive appearance that can serve as an alternative to tropical hardwoods. With these enhancements, thermowood offers a unique combination of long-lasting performance, natural beauty, and sustainability for decking projects.

Read more about thermowood decking.

Types of wood for decking

Our decking boards undergo intense thermal modification, giving them unrivaled durability and stability running all the way through to the core. Each board is naturally beautiful, expertly modified and highly functional – the perfect blend of art and science.

Thermo-ash

Thermally modified ash is the most popular choice for decking. This premium hardwood is made even more durable thanks to thermal modification and is tested to have Class 1 durability, meaning 25+ years of resistance to decay. Thermal modification gives ash a rich, deep brown color which makes it the perfect alternative to tropical woods like ipe and cumaru. Ash has the same look and feel, but is a more sustainable choice.

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Thermo-pine

The Nordic favourite has a very good price and quality ratio. It is more affordable than ash and has a durability of Class 2 – 15+ years of resistance to decay. When thermally modified, pine has a light, golden brown hue and is characterized by its knotty look. We source only Nordic pine, which is highly valued for its mechanical properties. This makes thermo-pine is a great substitute for Siberian larch.

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Thermo-spruce

Spruce is also a solid softwood option for decking. Thermo-spruce has a color and knotty look similar to pine, but better durability. It is tested for durability Class 1 – same resistance to decay as the thermo-ash. Thermo-spruce is an affordable decking material that’s perfect for demanding climatic conditions.

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Deck design and installation tips

Wood gives plenty of options for unique deck design. In addition to each species having a different visual look, the timber deck boards itself can be installed in different ways to achieve a desired architectural outcome. 

As thermowood decking boards as lightweight and come with straightforward installation guidelines, the wood is great to work with regardless of the size or shape of the deck. 

Key considerations for building a wood deck

• When designing a wood deck, focus on thoughtful layout planning to ensure both functionality and visual appeal. Consider how the deck will be used (entertaining, relaxing, dining), the flow between indoor and outdoor spaces, sun exposure, privacy, and how the deck integrates with the existing landscape. Here are some beautiful decking projects to inspire you!

• You can decide whether you want a traditional straight layout, diagonal, or a more intricate pattern. Patterns can add architectural interest and help visually define different zones on the deck. You can also opt for decking modules that are easy to snap into place – perfect for small balconies. 

• A solid, well-prepared subframe is essential for a long-lasting deck. We recommend building the subframe in thermowood as well, so it lasts as long as the decking boards themselves.

• Proper ventilation beneath the deck is crucial to prevent moisture buildup, which can lead to rot and structural issues. Ensure there is adequate clearance between the ground and the deck, and that air can circulate freely around and under the decking boards. 

• When it comes to fastening and fixing techniques, choose high-quality, stainless steel screws to securely fasten boards and prevent staining or corrosion.

See more installation tips from Thermory decking guidelines.

Deck building essentials – hidden fixing

If you want the decking to have a clean look, we recommend using decking boards that have hidden fixing.

Thermory PaCS® Strip is an innovative fastening solution with pre-grooved boards that enable a quick and easy deck installation with no visible screw heads and automatic alignment with a gap of 5 mm between the boards and substructure beams to ensure good ventilation. The strips, which fit together end to end, each consist of six clips that allow three boards to be attached sideways onto a single joist by simply securing the strips and then clicking the boards into place.

Installation systems for Thermory decking

Deck maintenance and longevity

The essence of why thermowood is the best material for decking isn’t just about the looks. Thermally modified wood has a long lifespan and, in addition, needs little maintenance besides regular cleaning. 

• No chemicals are used in the thermal modification process, only heat and steam. That also means that during the lifespan of the decking, no chemical treatments are needed. 

• Adding UV protection oil is optional. As with all wood, thermowood’s surface also naturally weathers to grey when exposed to sun, rain, snow and other elements. The more exposure, the quicker the change in color. If you are okay with the visual look of grey decking, you don’t need to oil the deck. The durability of the wood hasn’t declined. Decking oils can be used to keep the initial color of the thermowood. 

• Thermally modified boards can be simply washed with a wood cleaning product and warm water – if it’s particularly dirty you may also require a brush. Then, rinse with a garden hose on the spray setting. Use a low water pressure and test it on a small area beforehand to ensure it doesn’t cause damage – a strong jet of water can make the surface of the wood visibly uneven.

Sustainability and environmental impact of thermowood

As the construction industry faces urgent challenges around deforestation and carbon emissions, choosing a sustainable decking material has never been more important. Thermowood stands out for its performance and beauty, but also for its commitment to environmental responsibility throughout its entire lifecycle.

At Thermory, all timber is sourced from responsibly managed forests, prioritizing wood that is FSC® or PEFC™ certified. These certifications ensure that forests are replanted, biodiversity is protected, and local communities are supported.

Unlike many alternatives, thermowood is produced using only heat and steam — no chemicals, plastics, or harmful additives. This thermal modification process not only enhances durability and weather resistance but also minimizes environmental impact. Thermowood is safe for families, pets, and local ecosystems, both during installation and at the end of its long life.

Another key aspect of sustainability is product lifespan. Thermowood’s enhanced durability means decks last  longer than untreated wood or many composite options. Fewer replacements over time mean fewer trees harvested, less energy consumed, and less waste sent to landfill, maximizing the positive impact of your decking choice.

At the end of its service, thermowood is fully biodegradable. Unlike composite decking, which can persist in landfills for generations, thermowood naturally returns to the earth without leaving behind microplastics or chemical residues. This ensures your environmental impact remains positive from start to finish. Better yet, once the wood is not redeemed presentable enough for decking, we recommend reusing the material as flowerpots, fencing, garden shed cladding or other creative applications.