Home / Wood Compare / Thermowood Birch ThermoD vs Thermowood Siberian Larch ThermoD
Professional Comparison · Verified Engineering Data · Updated 19 July 2026
Thermowood Birch ThermoD VS Thermowood Siberian Larch ThermoD
Which wood is better for your project? Scores are computed from the verified figures on each species page — how we score.
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Thermowood Birch ThermoD
62/100 Library Score
🪵Hardwood🌧Outdoor💧Moisture Stable
- Better dimensional stability (Good vs Moderate)
- Stronger in bending (MOR 95.0 vs 78.0 MPa)
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Thermowood Siberian Larch ThermoD
38/100 Library Score
🌲Softwood🌧Outdoor
- Easier to machine and fasten
- Lighter (0.59 vs 0.62 g/cm³)
- Solid choice where its profile fits the project
Visual comparison
Thermowood Birch ThermoDThermowood Siberian Larch ThermoD
Winner by category
There isn't one universally best wood — there's a best wood for each purpose.
| Category | Winner |
|---|---|
| Durability | Tie |
| Stability | Thermowood Birch ThermoD |
| Hardness | Thermowood Birch ThermoD |
| Strength (MOR) | Thermowood Birch ThermoD |
| Stiffness (MOE) | Thermowood Birch ThermoD |
| Flame spread | Tie |
| Machining ease | Thermowood Siberian Larch ThermoD |
| Lightness | Thermowood Siberian Larch ThermoD |
Engineering data
| Property | Thermowood Birch ThermoD | Thermowood Siberian Larch ThermoD |
|---|---|---|
| Janka Hardness | 1210ITWA lbf | 1100ITWA lbf |
| Density | 0.62ITWA g/cm³ | 0.59ITWA g/cm³ |
| MOE | 12.0ITWA GPa | 11.5ITWA GPa |
| MOR | 95.0ITWA MPa | 78.0ITWA MPa |
| Durability | Class 2 Durable (treated) | Class 2 Durable (treated) |
| Stability | Good | Moderate |
| Fire (E84) | Class C indicative | Class C indicative |
| Radial Shrink | 1.6ITWA % | 1.4ITWA % |
| Tangential Shrink | 3ITWA % | 2.9ITWA % |
| T/R Ratio | 1.88 | 2.07 |
Figures carry the same source status as the species pages they come from — verified where cited, indicative where marked.
Best for
| Application | Recommended | Suitability |
|---|---|---|
| Outdoor decking / pergola | 🥇 Thermowood Birch ThermoD | ★★★★☆ |
| Exterior cladding | 🥇 Thermowood Birch ThermoD | ★★★☆☆ |
| Flooring / wear surfaces | 🥇 Thermowood Birch ThermoD | ★★★☆☆ |
| Furniture / interior joinery | 🥇 Thermowood Birch ThermoD | ★★★☆☆ |
| Structural / load-bearing | 🥇 Thermowood Birch ThermoD | ★★★☆☆ |
| Sauna / wet interiors | 🥇 Thermowood Birch ThermoD | ★★★★☆ |
Advantages & limitations
Thermowood Birch ThermoD
Advantages
- Rated for exterior exposure (EN 350 Class 2)
Limitations
- Few practical drawbacks within its intended uses
Thermowood Siberian Larch ThermoD
Advantages
- Rated for exterior exposure (EN 350 Class 2)
Limitations
- Noticeable seasonal movement — allow for it in design
Recommendation
Choose Thermowood Birch ThermoD if…
- You need minimal movement (doors, decking, panelling)
Choose Thermowood Siberian Larch ThermoD if…
- Ease of working and fastening matters
- Weight matters — ceilings, wall panels, transport
- Its profile matches the application better than a single overall score
Frequently asked questions
Which is more durable, Thermowood Birch ThermoD or Thermowood Siberian Larch ThermoD?
Neither — both carry the same EN 350 rating (Class 2, Durable (treated)). For outdoor decisions between them, weigh dimensional stability and hardness instead.
Which wood is better for outdoor use?
Thermowood Birch ThermoD — outdoor performance combines decay durability with dimensional stability, and it leads on that combination.
Is Thermowood Birch ThermoD harder than Thermowood Siberian Larch ThermoD?
Yes — Janka 1210 lbf vs 1100 lbf.
How we score. Each wood gets a weighted composite of the verified figures shown above: durability 22%, stability 18%, hardness 12%, bending strength 12%, machining ease 12%, stiffness 8%, flame spread 8%, lightness 8%. The Library Score is that composite's percentile rank within our 60-species library — 50 means the library median, 90 means it outperforms nine of every ten species we cover. No price data is scored — cost guidance is qualitative. The score summarises the data; it does not replace judgement about your specific application.