The base timber species commonly used for thermal modification (Thermowood), with the treatment class, typical mass loss, durability achieved and ideal applications for each.
Thermowood is not a species — it is a chemical-free heat treatment (typically 180–215°C under controlled steam) that permanently changes the wood's cell structure. The result: greatly reduced moisture movement, improved decay resistance, and a darker through-colour. ThermoS (~190°C) targets stability for interior and shaded use; ThermoD (~212°C+) targets durability for exterior cladding and decking. Mass loss during treatment is the key indicator of how far the modification has gone.
| Base Species ↕ | Treatment Class ↕ | Typical Mass Loss ↕ | Durability Achieved ↕ | EMC Reduction ↕ | Best For ↕ |
|---|---|---|---|---|---|
| Scots PinePinus sylvestris | ThermoD | 8-12% | Class 2 (Durable) | ~50% | Cladding, decking, sauna |
| Norway SprucePicea abies | ThermoD | 8-12% | Class 2-3 | ~45% | Cladding, garden structures |
| Radiata PinePinus radiata | ThermoD | 9-12% | Class 2 | ~50% | Decking, cladding |
| AshFraxinus excelsior | ThermoD | 7-10% | Class 1-2 | ~50% | Decking, flooring, furniture |
| PoplarPopulus spp. | ThermoS / ThermoD | 8-12% | Class 2-3 | ~45% | Cladding, lightweight panels |
| BirchBetula spp. | ThermoD | 8-11% | Class 2 | ~48% | Furniture, interior, panels |
| OakQuercus spp. | ThermoD | 6-9% | Class 1 | ~45% | Flooring, exterior furniture |
| MapleAcer spp. | ThermoD | 7-10% | Class 2 | ~48% | Flooring, joinery |
| AspenPopulus tremula | ThermoS | 8-11% | Class 2-3 | ~45% | Sauna interiors, cladding |
| EucalyptusEucalyptus spp. | ThermoD | 7-10% | Class 1-2 | ~48% | Decking, cladding |
