Thermowood by Stora Enso


Warm, safe and sound wood for decking, cladding and sauna interiors

Thermowood is thermo-treated wood produced using completely natural methods—heat and steam. The thermal treatment improves the wood’s properties, opening it up to a wide range of applications. Produced from premium quality, sustainable pine, or spruce with no harmful chemicals, Thermowood delivers high performance in any weather and ages with grace. 

Thermowood – the sign of genuine quality

Thermowood uses a patented production process and is a registered trademark that may only be used by licensed company members of the International ThermoWood Association (ITWA). An independent third party monitors its production so when you buy Thermowood from Stora Enso, you know that you’re getting a genuine quality product.

Great durability, dimensional stability and thermal performance

Thermowood is an environmentally sound alternative to pressure-impregnated wood and is resistant to demanding weather conditions, fungi and rot. Because of its decay resistance, low moisture content and thermal conductivity, Thermowood is a dimensionally stable and durable wood product with improved insulation properties. Thermowood keeps its shape and stands up to challenging climate conditions with recommended care and maintenance.

A versatile product, a variety of exterior and interior uses

Thermowood is a very popular choice for exterior cladding, decking, and facades. We provide standard and custom profiles as well as thermally modified raw material for further processing. Because Thermowood is resin and pith free, you can easily apply glue, paint, oil finishing or surface treatments like a fire-retardant coating or simply leave it natural. Thermowood is also an ideal material for interior panelling, flooring, furniture, and other building components. Due to its excellent properties, Thermowood is also a popular choice for sauna interiors.

Stora Enso’s Thermowood is available in two standard thermal treatment classes, Thermo-S and Thermo-D, to ensure the best technical performance. Thermo-S has improved stability, an attractive light golden-brown tone, and is mainly suitable for interiors. Thermo-D has improved durability, a darker brown tone, and is used in interior and exterior applications.

End use

  • External cladding and decking
  • Interior paneling
  • Industrial productions like joineries
  • Window and door manufacturers
  • Spa and sauna interiors

Key benefits

Key benefits of Thermowood

  • 100% natural processing with no chemical additives, biodegradable and recyclable

  • Third-party certification under FSC®, PEFC™ chain or custody or both ensures full traceability of the raw material from sustainably managed forests

  • Superior performance outdoors, indoors or in different weather conditions thanks to special thermal treatment

  • Possesses high dimensional stability, durability and decay resistance, has colour uniformity and reduced thermal conductivity 

  • No resin leakage, easy to paint or apply surface treatments

  • Stora Enso’s mills uphold ISO based management systems to ensure responsible, efficient, clean, and safe working environments (ISO 9001 quality, ISO 45001 safety and ISO 50001 energy efficiency).

Technical product data

Thermowood tech specs at a glance

Applications External and internal cladding and decking, industrial productions like joineries, window and door manufactures
Heat treatment classes Two standard thermal modification classes – Thermo-D and Thermo-S.
Standard dimensions Rough Thermowood out of pine and spruce is available as standard: 25x125 / x150; 32x125 / x150; 50x125 / x150
Planed sizes are often 19, 26, 42 mm thick and 117 and 140 mm wide.
Other sizes available on request
Use class Stora Enso Thermowood with Thermo-D treatment is suitable for use class 3 (EN 335).
Durability/resistance to rot Thermo-D is falling into durability class 2 (EN 350).
Without additional treatments Thermowood by Stora Enso is not resistant to termites.
Dimensional stability The thermal treatment process greatly reduces wood’s tendencies to warp, swell or shrink in different humidity conditions. The wood’s equilibrium moisture balance may be decreased to less than 40–50 % compared to untreated timber.
Thermal properties 0,09 W/(m K) according EN ISO 13787 + EN 12667
Leaching As no substances are added during the Thermowood process, no chemical leaching will occur. In addition, as the resin is removed during the process, the problem of resin leakage through the knots or pitch pockets is removed.
Ecological and safe Thermowood is produced using high temperature and steam. Since no chemicals are added during the process Thermowood contains only renewable substances. Disposal of offcuts can be burned or given into the normal waste system.
Certification PEFC, FSC, CE, KOMO, International Thermowood Association member


Sustainability is integral in Stora Enso’s business strategy—it is at the core of what we do. From our forest to your next project, we ensure environmental best practices in multiple ways.

All our wood supply chains are covered by a wood traceability system that is third-party verified according to PEFC, FSC®, ISO 14001 and are CE marked as they meet all European health, safety, and environmental protection standards. We ensure that the forests we harvest are duly regenerated.

Sustainability at Stora Enso

Documents and certificates

Image gallery

Thermowood by Stora Enso
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Thermowood by Stora Enso
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Business centre decking, Thermowood by Stora Enso
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Business Center decking in Paupys, Vilnius, Lithuania (Photographers:Ieva Saudargaitė, Darius Gumbrevičius) Architects: Plazma Architecture, Studio Developer: Darnu Group, Year: 2020
Thermowood by Stora Enso
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Thermowood by Stora Enso
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