ThermoWood Spruce Thermo-D VS Thermally Modified Western Red Cedar
- Stronger in bending (MOR 60.0 vs 45.0 MPa)
- Lighter (0.38 vs 0.42 g/cm³)
- Solid choice where its profile fits the project
Visual comparison
Winner by category
There isn't one universally best wood — there's a best wood for each purpose.
| Category | Winner |
|---|---|
| Durability | Tie |
| Stability | Tie |
| Hardness | ThermoWood Spruce Thermo-D |
| Strength (MOR) | ThermoWood Spruce Thermo-D |
| Stiffness (MOE) | ThermoWood Spruce Thermo-D |
| Flame spread | Tie |
| Machining ease | Thermally Modified Western Red Cedar |
| Lightness | Thermally Modified Western Red Cedar |
Engineering data
| Property | ThermoWood Spruce Thermo-D | Thermally Modified Western Red Cedar |
|---|---|---|
| Janka Hardness | 380UNV lbf | 350UNV lbf |
| Density | 0.42ITWA g/cm³ | 0.38ITWA g/cm³ |
| MOE | 10.1ITWA GPa | 7.5ITWA GPa |
| MOR | 47.5ITWA MPa | 45.0ITWA MPa |
| Durability | Class 2 Durable (treated) | Class 2 Durable (treated) |
| Stability | Moderate | Moderate |
| Fire (E84) | Not classified | Not classified |
| Radial Shrink | 1ITWA % | 1ITWA % |
| Tangential Shrink | 2.2ITWA % | 2ITWA % |
| T/R Ratio | 2.2 | 2.0 |
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 Spruce Thermo-D | ★★★☆☆ |
| Exterior cladding | 🥇 Thermally Modified Western Red Cedar | ★★★★☆ |
| Flooring / wear surfaces | 🥇 ThermoWood Spruce Thermo-D | ★☆☆☆☆ |
| Furniture / interior joinery | 🥇 Thermally Modified Western Red Cedar | ★★★★☆ |
| Structural / load-bearing | 🥇 ThermoWood Spruce Thermo-D | ★☆☆☆☆ |
Advantages & limitations
ThermoWood Spruce Thermo-D
Advantages relative to Thermally Modified Western Red Cedar
- MOE is 10.1 GPa vs 7.5 GPa, about 35% higher
Limitations relative to Thermally Modified Western Red Cedar
Thermally Modified Western Red Cedar
Advantages relative to ThermoWood Spruce Thermo-D
Limitations relative to ThermoWood Spruce Thermo-D
- MOE is 7.5 GPa vs 10.1 GPa, about 26% lower
Recommendation
Choose ThermoWood Spruce Thermo-D if…
- Exterior cladding and rain screens, decking, sauna interiors, garden structures where the higher stiffness matters in specification and the shared Class 2 thermally modified profile is the baseline
- Interior panelling and ceilings where the stiffer modified softwood is what the piece needs
Choose Thermally Modified Western Red Cedar if…
- Exterior cladding and rain screens where the modified western red cedar profile is what the project is specifying and the working properties are sufficient
- Interior panelling where the lighter softwood working profile is acceptable and the piece will not see high span or loading
Frequently asked questions
Which is more durable, ThermoWood Spruce Thermo-D or Thermally Modified Western Red Cedar?
Neither — both carry the same EN 350 rating (Class 2, Durable (treated)). Outdoors, movement will not separate them either — 2.2% against 2.0% tangential. The practical difference is weight: ThermoWood Spruce Thermo-D runs 0.42 g/cm³ against 0.38, so Thermally Modified Western Red Cedar is the easier fix overhead and the cheaper one to freight.
Which wood is better for outdoor use?
Both are EN 350 Class 2, and tangential movement runs 2.2% for ThermoWood Spruce Thermo-D against 2.0% for Thermally Modified Western Red Cedar — close enough that decay resistance will not choose between them, and Thermally Modified Western Red Cedar holds its dimension marginally better. Hardness is effectively level (380 vs 350 lbf), so choose on weight.
Is ThermoWood Spruce Thermo-D harder than Thermally Modified Western Red Cedar?
Yes — Janka 380 lbf vs 350 lbf.