ThermoWood Radiata Pine Thermo-D
Also known as thermo radiata, thermally modified radiata pine · Botanical Pinus radiata
Revision history
- — Data re-verified in site-wide audit (formulas, sources, durability classes)
- — Working properties and comparable-species data cross-checked against listed sources
About ThermoWood Radiata Pine Thermo-D
ThermoWood Radiata Pine Thermo-D is plantation radiata pine (Pinus radiata) modified at about 212°C. At 710 lbf (3,158 N) and 0.50 g/cm³ it is a little harder and heavier than Thermo Scots Pine, and it comes from a completely different supply chain: New Zealand and Chile rather than the Nordics.
Note: this is a modified product, and the panel above is modelled rather than measured. The hardness figure is the base species, because thermal modification changes hardness very little. For movement, the shrinkage and the fibre saturation point both fall after treatment, and that is why modified timber moves less across the same change in moisture. Published strength reductions vary by source; the table above uses our library figures for this pair. Modification also lowers bending strength and toughness relative to the untreated timber. Use this panel to size and to compare species, and take structural, fire, durability or movement figures from your supplier's declaration for the product you are actually buying.
The plantation origin is the point. Radiata is grown fast on a short rotation and milled young, which means clear, knot-free boards in long lengths are routinely available in a way Nordic pine never manages. Radial shrinkage of 1.2% and tangential of 2.6% after treatment are about a third of the natural figures.
At 440 kg/m³ a cubic metre of ThermoWood Radiata Pine Thermo-D weighs about 440 kg air-dry — that figure, the 2.6% tangential and 1.2% radial movement and the 710 lbf hardness are the three inputs the calculators below actually consume. Select ThermoWood Radiata Pine Thermo-D in any of them to get species-specific results for weight, moisture, shrinkage and hardness.
Working properties
Radiata is the blandest timber in the range and that is meant as a compliment. Fast, uniform, plantation growth gives even density and no surprises. How the board behaves once it is out of the kiln is set by the process itself, which is described in full in our guide to how ThermoWood is made. What follows is specific to this timber, drawn from the International ThermoWood Association, VTT Technical Research Centre of Finland and published thermal-modification research.
Durability & use classification
Radiata pine is in Table 1 of the ITWA ThermoWood Handbook, listed for Thermo-D only, not Thermo-S. Treated at around 212°C it is classified as durable, Class 2 under EN 113. There is a detail here that catches people out. A young radiata log is mostly sapwood, and its heartwood is not durable either, so untreated radiata outdoors is a non-starter without chemical treatment. Thermal modification is what makes it a cladding timber, and because the treatment works through the whole board rather than on a heartwood zone, that sapwood is not the problem it would be in a natural durable species. ITWA states ThermoWood is not intended for load-bearing structures, and the generic term under CEN/TS 15679 is Thermally Modified Timber. See our guide to how ThermoWood is made.
Against Nordic Thermo Pine the choice usually comes down to appearance and freight. Radiata gives you clear boards and a more even colour; Scots pine gives you knots, a shorter supply chain into Europe, and normally a lower price. Neither is technically better.
Typical applications & suitability
Indoor Outdoor — Plantation radiata pine is fast-grown, abundant and entirely non-durable in its natural state — making it an obvious modification candidate. The result is a certifiable, chemical-free exterior timber from a renewable plantation crop.
Documented end-uses: exterior cladding and rain screens, decking, garden structures, interior panelling and joinery.
Comparable species
Species closest to ThermoWood Radiata Pine Thermo-D by density, hardness, stiffness and bending strength, computed directly from the Vriksai species dataset rather than hand-picked.
Trade alternatives. Note the useful contrast: Accoya is the same species (Pinus radiata) modified a different way — acetylated to Class 1 with strength retained, versus thermally modified to Class 2 with some strength given up. Also compare ThermoWood Pine.
What modification did to Southern Yellow Pine
ThermoWood Radiata Pine Thermo-D is not a species — it is Southern Yellow Pine after heat treatment. Both sets of figures are in our library, so the effect of the process on this timber can be stated exactly rather than described in general terms.
| Property | Southern Yellow Pine | ThermoWood Radiata Pine Thermo-D | Change |
|---|---|---|---|
| Tangential movement | 7.7% | 2.6% | -66% |
| Radial movement | 5.4% | 1.2% | -78% |
| EN 350 durability | Class 4 | Class 2 | 2 class better |
| Bending strength (MOR) | 100 MPa | 62 MPa | -38% |
| Stiffness (MOE) | 12.3 GPa | 9.0 GPa | -27% |
| Janka hardness | 870 lbf | 710 lbf | -18% |
| Density | 0.51 g/cm³ | 0.50 g/cm³ | -2% |
On this species the process buys a 66% cut in tangential movement and a 2-class gain in durability, paid for with 38% of its bending strength and 18% of its surface hardness. That is a heavy strength penalty — specify it for cladding, screening and joinery, not for structural members.
The mechanism — hemicellulose breakdown, why durability is through-section rather than surface-deep, and why the strength loss happens — is set out once in our guide to thermal modification and the ThermoWood species reference, rather than repeated on each treated species page. Untreated figures: Southern Yellow Pine.
Alternatives to ThermoWood Radiata Pine Thermo-D
ThermoWood Radiata Pine Thermo-D measures 710 lbf Janka at 0.50 g/cm³, EN 350 durability Class 2, movement rated Moderate. ThermoWood Radiata Pine Thermo-D is a modified timber: its durability comes from process, its strength from the base species. Substitutes are matched on both, not on the treated figure alone. Read the numbers against the Janka scale and EN 350 durability classes.
Thermal modification lowers hardness slightly, so if the treated figure is short of what the job needs, these are the harder options at comparable service durability.
Lower-hardness options at similar treated durability — usually cheaper per m³ and faster through the shop.
Modification is already doing the stability work here. These achieve equal or lower movement by species or by deeper treatment. Size the gaps with the shrinkage predictor and EMC calculator.
If ThermoWood Radiata Pine Thermo-D is unavailable and the specification cannot change, these are the nearest substitutes across hardness, density, movement, stiffness, bending strength and durability class together — not on any single property. Lower distance means a closer match.
Computed from measured properties only — hardness, density, movement, stiffness, bending strength and EN 350 class. Price, availability and appearance are never inputs. Figures are representative values, not consignment absolutes: two species within a few percent are equivalent until verified on the material. Full method and the rules the engine cannot break.
Comparing modified timber to unmodified is a comparison of process as much as species — treatment class sets the durability, the base species sets the strength. Compare directly before substituting.
Compare ThermoWood Radiata Pine Thermo-D side by side
Modified against unmodified, and modification class against class — the comparisons that matter for treated timber. Every pairing shows the measured figures side by side; full matrix in the comparison index.
Calculators relevant to ThermoWood Radiata Pine Thermo-D
Includes the thermal-modification tools, since ThermoWood Radiata Pine Thermo-D behaves by treatment class as much as by species. Full set in the tool index.
Understand the figures
Moisture content — EMC, FSP and service conditions · Strength properties — MOR, MOE and what they govern · Durability & fire — EN 350 classes and E84 ratings · Thermal conductivity — k-value and insulation behaviour.
Further reading. What is ThermoWood? · ThermoWood vs Teak · Wood moisture content explained.
Common questions about ThermoWood Radiata Pine Thermo-D
A note on the strength figures. MOR and MOE above are the ITWA ThermoWood Handbook 2025 figures for the thermally modified board, measured to EN 408 — not the untreated base species. Hardness is a different matter: ITWA publishes Brinell hardness, not Janka, and the two Brinell figures we hold (ITWA and a licensed producer) disagree under the same cited standard, so both hardness rows are marked unverified until that is resolved. ThermoWood is not available as strength-graded timber and must not be used for load-bearing structures. If you are designing to a strength value, take it from your supplier's declaration for the actual product.
Brinell hardness not shown: the two authoritative sources we hold report figures that differ by a factor of about ten under the same cited standard (EN 1534). The disagreement is under investigation and no figure is published until it is resolved.
unverified no published source for this figure · ITWA International ThermoWood Association / VTT · calc derived from the figures above