Spruce-Pine-Fir SPF VS Paulownia
- Harder wear surface (Janka 510 vs 300 lbf)
- Stronger in bending (MOR 63.0 vs 38.0 MPa)
- Easier to machine and fasten
- Lighter (0.28 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 | Spruce-Pine-Fir SPF |
| Strength (MOR) | Spruce-Pine-Fir SPF |
| Stiffness (MOE) | Spruce-Pine-Fir SPF |
| Flame spread | Tie |
| Machining ease | Paulownia |
| Lightness | Paulownia |
Engineering data
| Property | Spruce-Pine-Fir SPF | Paulownia |
|---|---|---|
| Janka Hardness | 510grade lbf | 300WD lbf |
| Density | 0.42grade g/cm³ | 0.28WD g/cm³ |
| MOE | 9.5grade GPa | 4.38WD GPa |
| MOR | 63.0grade MPa | 38.0WD MPa |
| Durability | Class 4 Slightly Durable | Class 4 Slightly Durable |
| Stability | Excellent | Excellent |
| Fire (E84) | Class C indicative | Class C indicative |
| Radial Shrink | 4.4grade % | 2.4WD % |
| Tangential Shrink | 7.4grade % | 3.9WD % |
| T/R Ratio | 1.68 | 1.62 |
Figures carry the same source status as the species pages they come from — verified where cited, indicative where marked.
Best for
| Application | Recommended | Suitability |
|---|---|---|
| Exterior cladding | 🥇 Paulownia | ★★★☆☆ |
| Flooring / wear surfaces | 🥇 Spruce-Pine-Fir SPF | ★★☆☆☆ |
| Furniture / interior joinery | 🥇 Paulownia | ★★★★★ |
| Structural / load-bearing | 🥇 Spruce-Pine-Fir SPF | ★☆☆☆☆ |
Advantages & limitations
Spruce-Pine-Fir SPF
Advantages relative to Paulownia
- Janka is 510 lbf vs 300 lbf, about 70% harder
- MOR is 63 MPa vs 38 MPa, about 66% higher
- MOE is 9.5 GPa vs 4.4 GPa, about 116% higher
Limitations relative to Paulownia
Paulownia
Advantages relative to Spruce-Pine-Fir SPF
- Density is 0.28 g/cm³ vs 0.42, about 33% lower — supporting the documented lightweight applications where low mass matters more than bending strength
Limitations relative to Spruce-Pine-Fir SPF
- Janka is 300 lbf vs 510 lbf, about 41% lower
- MOR is 38 MPa vs 63 MPa, about 40% lower
- MOE is 4.4 GPa vs 9.5 GPa, about 54% lower
Recommendation
Choose Spruce-Pine-Fir SPF if…
- House construction and wall framing, trusses, joists and rafters, general framing and carcassing where the higher strength and stiffness are the specification and Class 4 durability with treatment is acceptable
- Panelling, mouldings and remanufacture where the harder softwood surface is what the piece needs
Choose Paulownia if…
- Lighter work — surfboard and model cores, veneer and panel cores, tansu chests and light joinery, panels and mouldings — where the low weight is the working advantage, matching the timber's documented sweet spot
- Musical instrument soundboards (documented for the koto) and cabinet interiors where the low weight and stable interior behaviour are the deciding factors
Frequently asked questions
Which is more durable, Spruce-Pine-Fir SPF or Paulownia?
Neither — both carry the same EN 350 rating (Class 4, Slightly Durable). For outdoor work the separation is movement, not decay: Paulownia moves 3.9% tangentially against 7.4%, which decides board width and fixing spacing more than the durability class does.
Which wood is better for outdoor use?
Both are EN 350 Class 4, and tangential movement runs 7.4% for Spruce-Pine-Fir SPF against 3.9% for Paulownia — close enough that decay resistance will not choose between them, and Paulownia holds its dimension marginally better. Spruce-Pine-Fir SPF gives the harder wearing surface at 510 lbf; Paulownia is the lighter section at 0.28 g/cm³ — traffic favours the first, cladding and handling the second.
Is Spruce-Pine-Fir SPF harder than Paulownia?
Yes — Janka 510 lbf vs 300 lbf.