ThermoWood is produced by heat treating Finnish grown European Redwood/Whitewood (Scandinavian Pine/Spruce) to temperatures in excess of 200 degrees Centigrade. During heat treatment, chemical and structural changes occur within the timber which alter and improve some of its basic characteristics.

As a result of the treatment, the resulting environmentally-friendly ThermoWood is created. Its colour darkens, it is more stable than normal wood in conditions of changing humidity and its thermal insulation properties are improved, ideal for use in exposed areas such as External Timber Cladding.

The heat treatment process enables the use of Scandinavian Redwood in areas requiring a service life of up to 30 years without the need for any further preservative or coating to be applied. The process removes resin from timber. As a result there is no resin leakage or “bleed” through the surface coatings. The combined effect of this together with the improved stability can lead to a lower maintenance requirement.

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Detailed Information

Wood Type
Sourced from well managed forests – PEFC® certified
Sawn and planed products in a wide range of thicknesses, widths and profiled patterns.
Medium/ Dark brown.
NORclad typically offer Thermowood D.
Typical end uses
External Joinery and Cladding.
350 – 480kg/m3 when moisture content is 6%.
Dimensional stability
Thermal modification increases stability.
Stainless steel fixings are always recommended.
Strength & working properties
With the lower moisture content after Thermal Modification the timber can be more brittle than unmodified Redwood/ Whitewood.
Typical section sizes
Ex 25, 32mm x 50, 75, 100, 125, 150mm.
Typical Lengths
2.4m +


All grading information is given as general guidance, to meet the criteria set through CE marking, quality and grading requirements.

All grading information is given as general guidance, to meet the criteria set through CE marking, quality and grading requirements.

NORclad offer Thermowood D;

  • PEFC Certified, sustainably sourced Timber
  • Imported from Scandinavia
  • All timber is sourced and machined to CE Quality Grading Requirements
  • Thermally Modified to 6% Moisture content
  • Typically 2.4m+ lengths
  • Frequent knots, creating character and variation from one board to the next.

Treatments & Coatings


Treatments can be applied to various cladding species to enhance or alter their colour or give them long term protection against the elements.

The treatment process impregnates wood cladding with a blend of preservative and Brunnea pigment.

From experience to date, exposure trials and commercial practice, you can expect the appearance of Brunnea treated wood to enrich after initial exposure.

NORclad Lite provides a 30 year warranty against rot & fungal decay.

The treatment process impregnates wood cladding with preservative and copper.
Without any pigment in the treatment, your timber cladding will naturally weather to a silver grey over time.


Thermowood is a great product to apply coatings too, due to its increased dimensional stability, at NORclad we are able to offer a quality controlled environment to coat timber, ensuring consistent quality throughout the order, offering significant saving in time, labour, and money VS on site application.

  • A quality controlled environment which is quick and efficient, ensuring consistent quality throughout the order from the first board, to the last.
  • Significant saving in time, labour, and money.

For coated options on Thermowood we primarily work with Sansin Paint Systems, and their SDF system. The coatings will protect the outside of wood, along with protecting the inside by allowing it to ‘breath’ – helping to prevent moisture from getting trapped in the wood and causing rot. Benefits of the SDF System include;

  • UV resistant
  • 130+ Finishes in the range
  • Highly water-repellent
  • Low in VOC content

Further information on coated Thermowood here

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Get in touch for other requirements, including bespoke profiles, halflap profiles, various sized PSE boards and Window reveals/cill.


If you have decided that Timber Cladding is going to be one of the materials on your project the next step is to create a specification that will meet the criteria and expectations you, and your client have.

NORclad will be happy to talk through what is available and enable you to select, amongst others: species, profile, size, treatment, requirement for Euro Class B, service life.

We offer installation guidance, detailing guidance based on TRADA documentation, with a wealth of knowledge and information on how different timbers will perform over the life span of your project.

Considerations that should be made when it comes to weather, along with how elevation and design variations can impact timber cladding.

Please get in contact if you would like NORclad to create an H21 specification for you, or download direct via NBS here.

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