Reference Data
Durability & Fire
Natural durability class (EN 350) and indicative fire performance (ASTM E84 flame-spread class) for 60 timber species. The two factors that decide whether a wood survives outdoors and how it behaves in fire.
Revision history
- — Site-wide audit — all tabulated values re-checked against listed sources
60Species rated
15Very Durable (Class 1)
EN 350Durability standard
ASTM E84Fire test basis
Natural durability (EN 350) grades heartwood resistance to decay fungi from Class 1 (Very Durable, 25+ years in ground contact) to Class 5 (Not Durable, under 5 years). Teak, ipe and the rosewoods are Class 1; pale temperate woods like beech, ash and birch are Class 5 and need treatment outdoors. Sapwood of every species is treated as Class 5. Fire class shown is an indication from the ASTM E84 flame-spread scale — Class A (best, flame-spread index 0–25), B (26–75), C (76–200). Dense, oily woods such as ipe genuinely test at Class A; most timber falls in B–C.
| Species ↕ | Durability Class ↕ | Rating ↕ | Ground Life ↕ | Fire (E84) ↕ | Specific Gravity ↕ |
|---|---|---|---|---|---|
| Lignum VitaeGuaiacum officinale | Class 1 | Very Durable | 25+ yrs | Class A | 1.05 |
| African BlackwoodDalbergia melanoxylon | Class 1 | Very Durable | 25+ yrs | Class A | 0.98 |
| Ipe LapachoHandroanthus serratifolius | Class 1 | Very Durable | 25+ yrs | Class A | 0.92 |
| EbonyDiospyros ebenum | Class 1 | Very Durable | 25+ yrs | Class A | 0.90 |
| CumaruDipteryx odorata | Class 1 | Very Durable | 25+ yrs | Class A | 0.87 |
| MassarandubaManilkara bidentata | Class 1 | Very Durable | 25+ yrs | Class A | 0.85 |
| JarrahEucalyptus marginata | Class 1 | Very Durable | 25+ yrs | Class B | 0.82 |
| WengeMillettia laurentii | Class 1 | Very Durable | 25+ yrs | Class B | 0.80 |
| Indian RosewoodDalbergia latifolia | Class 1 | Very Durable | 25+ yrs | Class B | 0.75 |
| MerbauIntsia bijuga | Class 1 | Very Durable | 25+ yrs | Class B | 0.74 |
| Thermally Modified OakQuercus robur | Class 1 | Very Durable (treated) | 25+ yrs | Class C | 0.68 |
| Burma Teak Premium GradeTectona grandis | Class 1 | Very Durable | 25+ yrs | Class B | 0.66 |
| TeakTectona grandis | Class 1 | Very Durable | 25+ yrs | Class B | 0.55 |
| IrokoMilicia excelsa | Class 1 | Very Durable | 25+ yrs | Class B | 0.55 |
| Accoya Acetylated Radiata PinePinus radiata | Class 1 | Very Durable (treated) | 25+ yrs | Class C | 0.51 |
| BangkiraiShorea laevis | Class 2 | Durable | 15-25 yrs | Class A | 0.85 |
| Spotted GumCorymbia citriodora | Class 2 | Durable | 15-25 yrs | Class B | 0.85 |
| BalauShorea spp. | Class 2 | Durable | 15-25 yrs | Class B | 0.78 |
| Shisham SissooDalbergia sissoo | Class 2 | Durable | 15-25 yrs | Class B | 0.75 |
| SalShorea robusta | Class 2 | Durable | 15-25 yrs | Class B | 0.74 |
| GarapaApuleia leiocarpa | Class 2 | Durable | 15-25 yrs | Class B | 0.72 |
| NeemAzadirachta indica | Class 2 | Durable | 15-25 yrs | Class C | 0.68 |
| European OakQuercus robur | Class 2 | Durable | 15-25 yrs | Class B | 0.67 |
| ThermoWood Ash Thermo-DFraxinus excelsior | Class 2 | Durable (treated) | 15-25 yrs | Class C | 0.66 |
| ThermoWood Birch Thermo-DBetula pubescens | Class 2 | Durable (treated) | 15-25 yrs | Class C | 0.62 |
| Thermally Modified Siberian LarchLarix sibirica | Class 2 | Durable (treated) | 15-25 yrs | Class C | 0.59 |
| Sweet ChestnutCastanea sativa | Class 2 | Durable | 15-25 yrs | Class B | 0.56 |
| Thermally Modified LarchLarix decidua | Class 2 | Durable (treated) | 15-25 yrs | Class C | 0.55 |
| ThermoWood Radiata Pine Thermo-DPinus radiata | Class 2 | Durable (treated) | 15-25 yrs | Class C | 0.50 |
| Deodar CedarCedrus deodara | Class 2 | Durable | 15-25 yrs | Class C | 0.48 |
| ThermoWood Pine Thermo-DPinus sylvestris | Class 2 | Durable (treated) | 15-25 yrs | Class C | 0.48 |
| ThermoWood Spruce Thermo-DPicea abies | Class 2 | Durable (treated) | 15-25 yrs | Class C | 0.45 |
| Hinoki CypressChamaecyparis obtusa | Class 2 | Durable | 15-25 yrs | Class C | 0.42 |
| Thermally Modified Western Red CedarThuja plicata | Class 2 | Durable (treated) | 15-25 yrs | Class C | 0.38 |
| Western Red CedarThuja plicata | Class 2 | Durable | 15-25 yrs | Class C | 0.32 |
| KeruingDipterocarpus spp. | Class 3 | Moderately Durable | 10-15 yrs | Class C | 0.69 |
| SapeleEntandrophragma cylindricum | Class 3 | Moderately Durable | 10-15 yrs | Class B | 0.62 |
| Black WalnutJuglans nigra | Class 3 | Moderately Durable | 10-15 yrs | Class B | 0.55 |
| European LarchLarix decidua | Class 3 | Moderately Durable | 10-15 yrs | Class C | 0.55 |
| Meranti Red LauanShorea spp. | Class 3 | Moderately Durable | 10-15 yrs | Class C | 0.52 |
| African MahoganyKhaya ivorensis | Class 3 | Moderately Durable | 10-15 yrs | Class B | 0.52 |
| American CherryPrunus serotina | Class 3 | Moderately Durable | 10-15 yrs | Class B | 0.50 |
| Douglas FirPseudotsuga menziesii | Class 3 | Moderately Durable | 10-15 yrs | Class C | 0.48 |
| Sugi Japanese CedarCryptomeria japonica | Class 3 | Moderately Durable | 10-15 yrs | Class C | 0.38 |
| Bamboo Structural EngineeredBambusa / Dendrocalamus spp. | Class 4 | Slightly Durable | 5-10 yrs | Class C | 0.60 |
| Southern Yellow PinePinus spp. (P. palustris, P. taeda) | Class 4 | Slightly Durable | 5-10 yrs | Class C | 0.51 |
| Scots PinePinus sylvestris | Class 4 | Slightly Durable | 5-10 yrs | Class C | 0.49 |
| Kail Blue PinePinus wallichiana | Class 4 | Slightly Durable | 5-10 yrs | Class C | 0.45 |
| Hem-FirTsuga / Abies spp. | Class 4 | Slightly Durable | 5-10 yrs | Class C | 0.45 |
| Western HemlockTsuga heterophylla | Class 4 | Slightly Durable | 5-10 yrs | Class C | 0.45 |
| Norway SprucePicea abies | Class 4 | Slightly Durable | 5-10 yrs | Class C | 0.43 |
| Spruce-Pine-Fir SPFPicea / Pinus / Abies spp. | Class 4 | Slightly Durable | 5-10 yrs | Class C | 0.42 |
| PaulowniaPaulownia tomentosa | Class 4 | Slightly Durable | 5-10 yrs | Class C | 0.28 |
| European BeechFagus sylvatica | Class 5 | Not Durable | <5 yrs | Class B | 0.68 |
| Hard MapleAcer saccharum | Class 5 | Not Durable | <5 yrs | Class B | 0.63 |
| Yellow BirchBetula alleghaniensis | Class 5 | Not Durable | <5 yrs | Class B | 0.62 |
| Silver BirchBetula pendula | Class 5 | Not Durable | <5 yrs | Class B | 0.61 |
| White AshFraxinus americana | Class 5 | Not Durable | <5 yrs | Class B | 0.60 |
| Rubber WoodHevea brasiliensis | Class 5 | Not Durable | <5 yrs | Class C | 0.55 |
| Mango WoodMangifera indica | Class 5 | Not Durable | <5 yrs | Class C | 0.51 |
Important: Durability classes apply to heartwood only — sapwood is non-durable for every species. Fire-class figures are indicative, based on density and published test data; real fire performance depends on the actual product, its thickness, any coating, and how it is installed, so a building specification needs a certified ASTM E84 (or EN 13501 Euroclass) test report for that specific product — fire performance is a tested property, not a fixed species constant. Durability also varies with origin, tree age and exposure — treat these as guidance, not a guarantee.
Related tools
Sources
- EN 350:2016 — durability of wood
- USDA FPL Wood Handbook GTR-190 — www.fpl.fs.usda.gov/documnts/fplgtr/fplgtr190
Common questions
What do durability classes 1 to 5 mean?
Class 1 means the wood can sit in wet, tough conditions for decades — teak is a classic example. Class 5 means it rots quickly outdoors. The scale comes from the European EN 350 standard.
Can a non-durable wood still be used outside?
Yes, if you protect it. Keep it off the ground, let water drain, use a good coating, or choose treated wood. Design does as much work as the species.
Is hardwood always more durable than softwood?
No. Some softwoods like western red cedar last very well outdoors, and some hardwoods rot fast. Durability depends on the natural oils and extractives in the wood, not on the hardwood/softwood label.