Home / Wood Compare / ThermoWood Birch Thermo-D vs Thermally Modified Siberian Larch
Professional Comparison · Source-attributed engineering data · Updated 19 July 2026
ThermoWood Birch Thermo-D VS Thermally Modified Siberian Larch
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 Thermo-D
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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Thermally Modified Siberian Larch
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 Thermo-DThermally Modified Siberian Larch
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 Thermo-D |
| Hardness | ThermoWood Birch Thermo-D |
| Strength (MOR) | ThermoWood Birch Thermo-D |
| Stiffness (MOE) | ThermoWood Birch Thermo-D |
| Flame spread | Tie |
| Machining ease | Thermally Modified Siberian Larch |
| Lightness | Thermally Modified Siberian Larch |
Engineering data
| Property | ThermoWood Birch Thermo-D | Thermally Modified Siberian Larch |
|---|---|---|
| Janka Hardness | 1210UNV lbf | 1100UNV 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) | Not classified | Not classified |
| 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 Thermo-D | ★★★★☆ |
| Exterior cladding | 🥇 ThermoWood Birch Thermo-D | ★★★☆☆ |
| Flooring / wear surfaces | 🥇 ThermoWood Birch Thermo-D | ★★★☆☆ |
| Furniture / interior joinery | 🥇 ThermoWood Birch Thermo-D | ★★★☆☆ |
| Structural / load-bearing | 🥇 ThermoWood Birch Thermo-D | ★★★☆☆ |
| Sauna / wet interiors | 🥇 ThermoWood Birch Thermo-D | ★★★★☆ |
Advantages & limitations
ThermoWood Birch Thermo-D
Advantages relative to Thermally Modified Siberian Larch
- MOR is 95 MPa vs 78 MPa, about 22% higher
Limitations relative to Thermally Modified Siberian Larch
Thermally Modified Siberian Larch
Advantages relative to ThermoWood Birch Thermo-D
Limitations relative to ThermoWood Birch Thermo-D
- MOR is 78 MPa vs 95 MPa, about 18% lower
Recommendation
Choose ThermoWood Birch Thermo-D if…
- Exterior cladding, interior panelling and flooring, sauna benches and interiors where the higher bending strength matters in specification and the shared Class 2 thermally modified profile is the baseline
- Furniture and joinery where the birch grain and appearance are the aesthetic preference
Choose Thermally Modified Siberian Larch if…
- Exterior cladding, rain screens, decking, flooring and interior panelling where the shared thermally modified profile matches the specification and the working properties are sufficient
- Garden structures where the softwood cost profile is acceptable and the larch grain is the aesthetic preference
Frequently asked questions
Which is more durable, ThermoWood Birch Thermo-D or Thermally Modified Siberian Larch?
Neither — both carry the same EN 350 rating (Class 2, Durable (treated)). Outdoors, movement will not separate them either — 3.0% against 2.9% tangential. The practical difference is weight: ThermoWood Birch Thermo-D runs 0.62 g/cm³ against 0.59, so Thermally Modified Siberian Larch is the easier fix overhead and the cheaper one to freight.
Which wood is better for outdoor use?
ThermoWood Birch Thermo-D — outdoor performance combines decay durability with dimensional stability, and it leads on that combination.
Is ThermoWood Birch Thermo-D harder than Thermally Modified Siberian Larch?
Yes — Janka 1210 lbf vs 1100 lbf.
How we score. Scores shown are percentile ranks within our library, weighted towards durability and dimensional stability. They shortlist; they do not decide. Full weighting and what it excludes.