by Eric Meier
How do you define wood strength?
The simplest and most common way people define if a wood is “strong” is usually hardness. I’ve written about wood hardness before—as a matter of fact, I even have an entire poster ranking the hardness of all sorts of woods worldwide. But this is a very one-dimensional way of approaching the question.
Here are some questions to consider:
- What if we want to make a ramp where heavy machinery will be wheeled across the wood? We don’t want the planks to break.
- How about a bookshelf, where a continuous load will be applied? We don’t want the wood to bow or sag.
- What if we are making chair legs which will need to support a lot of weight parallel to the grain? We don’t want the wood to be crushed and give out.
All of the above scenarios have nothing to do with wood hardness. They are real-world examples that parallel totally separate wood tests (modulus of rupture, modulus of elasticity, and crushing strength, respectively).
Strength and density: imperfectly correlated
When it comes to the relationship between wood hardness and density, the two statistics are very closely correlated—so much so that the USDA has a publication on estimating wood hardness based on a wood’s specific gravity. However, the same level of correlation cannot be claimed for most other strength properties.
Here’s an example of two woods to illustrate this point:
Average dried weight: 79 lbs/ft3 (1,260 kg/m3)
Janka hardness: 4,390 lbf (19,510 N)
Modulus of elasticity: 2,481,000 lbf/in2 (17.11 GPa)
Average dried weight: 54 lbs/ft3 (870 kg/m3)
Janka hardness: 1,930 lbf (8,600 N)
Modulus of elasticity: 2,550,000 lbf/in2 (17.59 GPa)
When comparing the two wood species above, it should be apparent that there’s somewhat of a contradiction in the data. Lignum vitae is one of the heaviest, hardest woods in the world. By comparison, while wenge is still a rather hard and heavy wood, it’s considerably lighter and softer than the lignum vitae—yet its modulus of elasticity (on average) is higher than that of lignum vitae. So what’s the explanation?
Wood strength is complicated
Think of wood as a very intricately patterned structure, composed of different components in varying lengths, thicknesses, and intertwining patterns. It’s difficult to speak in generalities with a high degree of certainty, but here are some things to consider in a wood’s grain and its influence on strength.
- An increased microfibril angle (MFA) in the wood’s cell walls may lead to a decrease in modulus of elasticity.
- Heartwood extractives may deposit substances into the wood that can reinforce and strengthen the wood fibers.
- Conversely, heartwood extractives may deposit substances that otherwise bloat wood density without positively impacting strength.
- Large groups of rays, parenchyma cells, or very large earlywood pore rows may create localized weak points in the wood on a small scale that are negated in larger pieces of timber.
- Knots and other defects are sometimes unavoidable in some species, and will effect different strength properties to varying degrees (e.g., a knot may increase a wood’s hardness in that area, but decrease its overall bending strength).
Coming up with a good definition of “strong”
It should be apparent that wood strength is so much more than simply wood hardness. But there are a nearly endless number of ways to test and measure different properties of woods. You can test for stiffness, hardness, rupture resistance, impact resistance, shear resistance, crush resistance, wear resistance, and tensile strength. Also, most of these properties will have different strengths on different axes—whether parallel or perpendicular to the grain, etc.
So what’s the best definition of strong? In an ideal world, every single wood species would have meticulous data published on every possible facet of its mechanical properties, but that’s just not practical. There are all sorts of gaps and missing data, and we have no way of reliably predicting what these values will be—this is especially true of the more obscure tests. The best definition lies somewhere between using everything (impractical) and just hardness (too simplistic).
The sweet spot: the big three
Amidst the sea of all the wood strength tests performed worldwide over the decades, there are three tests that consistently show up in nearly every evaluation. (Not surprisingly, they are also the three strength tests that I’ve chosen to include throughout the Wood Database.) The big three, listed in what I believe is their order of importance, are:
So these three terms, along with Janka hardness, will form the four ingredients that we will use to come up with an overall picture of a wood’s strength level. We need to create a multi-faceted profile to come up with a well-rounded representation of what is “strong.”
The problem is that each of these tests use completely different units of measurements, scales of magnitude, and are generally not directly comparable. Each of these facets will need to be standardized on a scale that preserves their significance, but strips them of their units of measurement.
So, let’s find the world’s strongest wood
What I’ve done is taken each of the four tests of wood strength (Janka hardness, MOE, MOR, and crushing strength) and found which species were the best and worst in that category, and then use those values as the upper and lower limits. (This is limited to the data I have on hand at the present, and could be revised or updated at a later time.) All the values in each category were then subtracted by the amount of the lower limit to serve as a baseline zero.
Next, each of the values were divided by the upper limit for each category, and then that value is multiplied by 100 to serve as a percentage, and voila! We have a straightforward ranking from 0-100 in each of the four categories. This ranking would represent, as a percentage, how strong a given wood is in comparison to the species with the top mark for that category.
Averaging across the four categories gives us an overall “strength index” from 0-100. A perfect score of 100 would be theoretically impossible unless a single wood species was the leader in all of the four tests (hint: none of them led in even two categories).
Let’s first review the leaders in each category:
Common Name: Waddywood
Scientific Name: Acacia peuce
Best-in-class Janka hardness: 4,630 lbf (20,600 N)
Notes: Despite its colossal hardness value (as well as its extreme density), waddywood has absolutely no available strength test data available. And so unfortunately, it has to be disqualified from the strength rankings due to lack of data. There simply isn’t a strong enough correlation between density and various strength properties to make an accurate estimate that would do justice to this unique wood (as the comparison between lignum vitae and wenge listed above illustrates).
Modulus of elasticity
Common Name: Coracao de negro
Scientific Name: Swartzia panacoco
Best-in-class MOE: 4,517,000 lbf/in2 (31.15 GPa)
Notes: This South American native is a very close relative to the better-known exotic katalox—but with a slight bump-up in nearly every category. A serious contender for the title of world’s strongest wood—which is a pattern to note across the entire Swartzia genus and the slightly broader Swartzieae tribe. The only caveat is that I could not find any published data on hardness for this particular species, so an estimated value (presumably slightly under-estimated, especially when compared with other Swartzia species) had to be used.
Modulus of rupture
Common Name: Pintobortri
Scientific Name: Pouteria eugenifolia
Best-in-class MOR: 37,560 lbf/in2 (259.0 MPa)
Notes: An extremely obscure species, the associated wood picture here is technically from a related species in the same genus, P. sapota. At the moment, the only confirmed images of this wood I could find online were a pair of black and white photos taken from the Samuel J Record wood collection—a collection of samples that was acquired by the USDA’s Forest Products Laboratory back in 1969, and whose specimens probably date to decades earlier. A few caveats: first, the data comes from only a single source; secondly, the hardness is estimated from density. (In this case, with its extremely high reported specific gravity, the estimated hardness may be over-estimated—theoretically it exceeds even the class-leading waddywood listed above.) Any record-holding will be with an asterisk.
Common Name: Suriname ironwood
Scientific Name: Bocoa prouacensis
Best-in-class Crushing Strength: 19,000 lbf/in2 131.1 MPa)
Notes: Another South American native, this species is a close relative to katalox, with both species being included in the tribe Swartzieae (though in separate genera). But along with the other top contenders listed above, Suriname ironwood comes with the caveat that there is no known hardness value published, so an estimated value was used based on specific gravity. So along with the other leaders, this puts any would-be record-holding in asterisk territory.
Bottom of the heap
Common Name: Quipo
Scientific Name: Cavanillesia platanifolia
Notes: While each of the four titles for strength categories were awarded to different wood species, when it came to the lowest values, it was a sweep across the board—earning quipo a perfect strength index score of 0. Quipo wood was the subject of a 1955 USDA study that evaluated its suitability as a replacement for balsa, and while it was found that the wood had a similar light weight, it was also equal or slightly weaker in nearly all metrics. (Note, the wood pictured is actually that of Tilia cordata, a species of basswood or linden that’s in the botanically-related Malvaceae family.)
And with all of the groundwork, rationale, and explanations out of the way, let’s finally take a look at the all the data and see where all of the woods rank!
Wood power rankings chart
|91.3||Suriname ironwood||Bocoa prouacensis||93.9||84.9||86.3||100.0|
|83.3||Coracao de negro||Swartzia panacoco||73.2||100.0||76.9||83.1|
|75.5||Endra endra||Humbertia madagascariensis||94.1||64.5||68.2||75.2|
|67.3||African Blackwood||Dalbergia melanoxylon||79.0||55.2||81.6||53.3|
|66.6||Grey Ironbark||Eucalyptus paniculata||64.5||68.3||66.9||66.7|
|65.7||Iron birch||Betula schmidtii||51.2||55.0||89.6||66.9|
|65.3||Red Mangrove||Rhizophora mangle||59.2||77.1||62.8||62.3|
|65.2||Chico Zapote||Manilkara zapota||63.8||63.6||69.8||63.6|
|63.9||Lignum Vitae||Guaiacum officinale||94.7||52.4||45.4||63.3|
|63.7||Siamese Rosewood||Dalbergia cochinchinensis||51.9||49.9||64.4||88.7|
|62.5||Angelim vermelho||Dinizia excelsa||67.9||60.1||58.1||63.7|
|61.8||Pau Rosa||Bobgunnia fistuloides||63.1||52.4||62.5||69.2|
|61.2||Horsetail Casuarina||Casuarina equisetifolia||68.8||58.7||58.6||58.7|
|60.2||Grey Box||Eucalyptus moluccana||71.1||55.5||56.6||57.5|
|60.1||Macassar Ebony||Diospyros celebica||69.2||53.2||58.8||59.1|
|59.6||Black Ironwood||Krugiodendron ferreum||78.8||63.7||46.0||49.8|
|59.1||Rose sheoak||Allocasuarina torulosa||67.6||62.2||53.9||52.6|
|58.4||Hormigo Negro||Platymiscium dimorphandrum||57.9||60.7||55.3||59.5|
|58.3||Gaboon Ebony||Diospyros crassiflora||66.2||51.6||59.2||56.0|
|56.8||East African Olive||Olea capensis||57.8||54.6||58.1||56.7|
|56.3||Pink Ivory||Berchemia zeyheri||69.4||45.7||51.1||59.2|
|55.5||Texas Ebony||Ebenopsis ebano||60.5||50.5||56.9||54.2|
|54.5||Gum Arabic||Vachellia nilotica||67.0||49.6||49.6||51.8|
|54.0||Santos Mahogany||Myroxylon balsamum||51.3||50.0||55.4||59.4|
|54.0||Spotted Gum||Corymbia maculata||49.7||61.4||52.6||52.4|
|53.7||Blue Gum||Eucalyptus globulus||50.7||58.0||49.7||56.5|
|53.0||Madagascar Rosewood||Dalbergia baronii||58.2||35.1||62.3||56.2|
|51.6||Ceylon Satinwood||Chloroxylon swietenia||56.1||43.7||54.0||52.4|
|51.3||Argentine Osage Orange||Maclura tinctoria||50.9||44.9||49.8||59.6|
|50.0||Brazilian Rosewood||Dalbergia nigra||59.8||41.6||49.8||48.7|
|49.8||Red ash||Alphitonia excelsa*||40.1||58.8||49.4||51.0|
|49.6||Yellow Box||Eucalyptus melliodora||62.7||41.9||44.6||49.3|
|48.4||Goncalo Alves||Astronium graveolens||46.2||50.5||42.6||54.4|
|48.1||Black Palm||Borassus flabellifer||43.1||47.3||50.9||51.2|
|47.5||Pignut Hickory||Carya glabra||45.6||47.2||51.3||45.6|
|47.3||Lemon-Scented Gum||Corymbia citriodora||40.7||50.9||49.6||47.9|
|47.0||River Sheoak||Casuarina cunninghamiana||42.4||35.2||48.7||61.7|
|46.8||Live Oak||Quercus virginiana||57.4||40.2||46.1||43.5|
|46.7||Ceylon Ebony||Diospyros ebenum||51.9||42.1||47.3||45.7|
|46.5||Panga Panga||Millettia stuhlmannii||34.8||47.7||48.3||55.0|
|46.1||Burma Padauk||Pterocarpus macrocarpus||45.8||42.3||51.4||44.8|
|46.0||Osage Orange||Maclura pomifera||56.1||33.9||47.3||46.7|
|45.6||Prosopis juliflora||Prosopis juliflora||56.1||35.5||42.0||48.8|
|45.6||Shagbark Hickory||Carya ovata||40.0||44.9||51.6||45.7|
|45.3||Mockernut Hickory||Carya tomentosa||41.9||46.3||48.8||44.3|
|45.1||Lebombo ironwood||Androstachys johnsonii||55.9||31.8||47.0||45.7|
|44.9||Amazon Rosewood||Dalbergia spruceana||57.8||38.1||42.5||41.3|
|44.7||Black Locust||Robinia pseudoacacia||36.0||42.3||49.4||51.2|
|44.6||Timborana||Pseudopiptadenia suaveolens (= Piptadenia spp.)||32.7||50.0||43.8||51.8|
|44.2||Yellow Gum||Eucalyptus leucoxylon||52.9||35.1||40.1||48.5|
|43.8||Afzelia xylay||Afzelia xylocarpa||42.2||39.7||43.3||49.9|
|42.5||East Indian Rosewood||Dalbergia latifolia||52.2||33.4||41.5||42.7|
|42.2||Black wattle||Acacia mearnsii||36.1||43.9||44.5||44.4|
|42.2||Tropical black sage||Cordia curassavica||47.0||31.3||44.4||46.1|
|42.0||Cherrybark Oak||Quercus pagoda||31.2||47.7||45.7||43.1|
|41.8||Red Bloodwood||Corymbia gummifera||52.4||37.9||35.3||41.7|
|41.7||River Red Gum||Eucalyptus camaldulensis||46.0||34.4||45.3||41.1|
|41.1||Rhodesian Teak||Baikiaea plurijuga||64.2||23.1||29.3||47.9|
|40.8||Indian Laurel||Terminalia elliptica||49.9||36.6||36.3||40.3|
|40.6||Canadian Serviceberry||Amelanchier canadensis||38.2||38.3||42.4||43.3|
|40.5||Shellbark Hickory||Carya laciniosa||38.4||38.6||45.7||39.0|
|40.4||Water Hickory||Carya aquatica||32.8||41.6||44.9||42.4|
|40.4||Field maple||Acer campestre||24.0||34.4||45.0||58.2|
|40.3||Pau Ferro||Machaerium spp.||41.7||31.2||44.8||43.7|
|40.2||Peroba Rosa||Aspidosperma polyneuron||35.5||41.2||38.9||45.3|
|40.2||Swamp White Oak||Quercus bicolor||33.9||41.8||43.8||41.2|
|40.1||Sweet Birch||Betula lenta||31.0||45.1||42.4||42.0|
|39.5||African Padauk||Pterocarpus soyauxii||41.9||34.1||42.2||39.7|
|38.9||Bitternut Hickory||Carya cordiformis||31.7||36.2||43.0||44.8|
|38.6||Swamp Mahogany||Eucalyptus robusta||26.1||42.3||44.0||42.0|
|38.5||Burmese Blackwood||Dalbergia cultrata||72.1||31.8||27.2||23.0|
|38.5||Queensland Walnut||Endiandra palmerstonii||35.1||33.1||35.9||49.8|
|38.5||European Beech||Fagus sylvatica||30.6||42.9||39.8||40.5|
|38.2||Red Palm||Cocos nucifera||40.3||33.1||31.4||47.9|
|37.9||Hard milkwood||Alstonia spectabilis||30.8||40.2||29.6||50.9|
|37.5||Andaman Padauk||Pterocarpus dalbergioides||34.5||35.4||36.5||43.6|
|37.3||Yellow Birch||Betula alleghaniensis||26.4||41.4||41.6||40.0|
|37.1||Rengas||Gluta spp. Melanorrhoea spp.||36.5||39.2||31.8||41.2|
|36.7||Rose Gum||Eucalyptus grandis||26.4||42.4||38.9||39.1|
|36.7||Pear Hawthorn||Crataegus calpodendron||35.5||26.4||43.4||41.4|
|36.5||Eastern Hophornbeam||Ostrya virginiana||39.5||34.1||34.6||37.7|
|36.4||Scarlet Oak||Quercus coccinea||29.5||35.7||40.1||40.4|
|36.3||Hard maple||Acer saccharum||30.6||37.2||39.3||38.1|
|36.3||European Hornbeam||Carpinus betulus||34.5||35.4||39.9||35.3|
|36.0||Australian blackwood||Acacia melanoxylon||24.3||44.6||37.2||37.8|
|35.9||Mountain Ash||Eucalyptus regnans||25.4||41.9||34.3||42.0|
|35.8||American Hornbeam||Carpinus caroliniana||37.8||34.0||40.7||30.7|
|35.7||Black siris||Albizia odoratissima||34.6||34.3||34.2||39.8|
|35.2||Water Oak||Quercus nigra||24.9||41.9||41.6||32.2|
|35.0||European Ash||Fraxinus excelsior||31.2||36.1||37.1||35.7|
|34.6||Honey Locust||Gleditsia triacanthos||33.4||32.5||36.3||36.3|
|34.4||Willow Oak||Quercus phellos||30.8||36.6||36.7||33.7|
|34.4||Turkey Oak||Quercus cerris||25.1||31.1||41.5||40.0|
|34.3||Pacific Yew||Taxus brevifolia||33.9||26.0||37.7||39.6|
|34.2||Slash Pine||Pinus elliottii||15.5||40.7||40.7||39.8|
|34.0||White Oak||Quercus alba||28.3||35.6||36.6||35.5|
|34.0||Longleaf Pine||Pinus palustris||17.9||40.7||35.7||41.7|
|33.9||Nutmeg Hickory||Carya myristiciformis||27.1||34.1||41.6||33.0|
|33.9||White Ash||Fraxinus americana||27.7||35.1||37.1||35.8|
|33.8||Norway maple||Acer platanoides||21.1||30.3||41.8||42.1|
|33.6||Winged Elm||Ulmus alata||32.5||33.0||36.5||32.3|
|33.5||Tasmanian Myrtle||Lophozonia cunninghamii||27.6||37.2||35.0||34.4|
|33.5||American Beech||Fagus grandifolia||27.3||34.6||36.8||35.2|
|33.2||Sumatran Pine||Pinus merkusii||19.7||44.9||34.3||34.1|
|33.1||Ocote Pine||Pinus oocarpa||19.7||46.0||36.3||30.2|
|33.0||Pin Oak||Quercus palustris||31.6||34.4||33.9||32.1|
|33.0||English Walnut||Juglans regia||25.5||31.1||40.3||35.1|
|32.6||Indian Silver Greywood||Terminalia bialata||28.6||39.2||31.1||31.4|
|32.6||Laurel Oak||Quercus laurifolia||25.3||36.3||35.2||33.4|
|32.5||Black Mesquite||Prosopis nigra||41.3||20.5||26.5||41.8|
|32.3||Swamp Chestnut Oak||Quercus michauxii||25.7||35.4||33.6||34.6|
|32.3||Caribbean Pine||Pinus caribaea||23.1||35.2||32.5||38.4|
|32.3||Western sheoak||Allocasuarina fraseriana||40.4||26.1||34.9||27.7|
|32.2||Red Oak||Quercus rubra||25.6||35.6||35.4||32.3|
|32.1||Rock Elm||Ulmus thomasii||27.7||30.4||36.5||33.8|
|31.8||Black Walnut||Juglans nigra||21.0||33.7||36.0||36.7|
|31.7||Green Ash||Fraxinus pennsylvanica||25.1||33.2||34.6||34.0|
|31.6||Nigerian pearwood||Guarea cedrata||19.5||31.4||37.0||38.5|
|31.6||Black Oak||Quercus velutina||25.3||35.0||35.5||30.5|
|31.5||Sweet Cherry||Prunus avium||24.0||30.1||37.0||34.9|
|31.5||Blackheart Sassafras||Atherosperma moschatum||22.8||37.1||35.9||30.2|
|31.3||Pacific maple||Aglaia cucullata||21.0||35.4||32.1||36.7|
|31.3||Alaska Paper Birch||Betula neoalaskana||17.0||38.8||33.2||36.0|
|31.2||White Seraya||Parashorea spp. (lucida, stellata)||18.3||37.4||31.9||37.2|
|30.9||Sycamore maple||Acer pseudoplatanus||21.9||28.0||34.9||38.9|
|30.9||Western Larch||Larix occidentalis||17.0||38.1||31.5||36.9|
|30.7||Red Mulberry||Morus rubra||35.6||26.0||27.8||33.5|
|30.4||Chakte Kok||Simira salvadorensis||25.3||29.4||35.2||31.8|
|30.3||Blue Ash||Fraxinus quadrangulata||27.1||27.1||33.7||33.4|
|30.3||Black maple||Acer nigrum||24.7||32.3||32.4||31.7|
|30.1||Sessile Oak||Quercus petraea||23.4||29.9||34.5||32.7|
|30.1||English Oak||Quercus robur||23.4||30.5||34.5||31.9|
|30.1||Post Oak||Quercus stellata||28.3||29.3||31.7||30.9|
|30.0||Chestnut Oak||Quercus prinus||23.6||31.6||32.4||32.6|
|30.0||Tree of Heaven||Ailanthus altissima||29.9||32.3||26.1||31.7|
|30.0||Crab apple||Malus sylvestris||36.7||24.1||31.0||28.1|
|29.9||Wych Elm||Ulmus glabra||20.5||32.2||35.0||31.9|
|29.7||Parana Pine||Araucaria angustifolia||16.6||32.9||32.6||36.7|
|29.7||African Mahogany||Khaya senegalensis||22.3||30.3||32.0||34.1|
|29.5||White Cypress Pine||Callitris columellaris||28.7||26.0||27.5||36.1|
|29.4||Cedar Elm||Ulmus crassifolia||27.7||29.0||32.9||28.1|
|29.4||European Larch||Larix decidua||15.1||34.4||31.7||36.5|
|29.1||Dark Red Meranti||Shorea spp.||16.5||35.1||30.7||33.9|
|29.0||Shortleaf Pine||Pinus echinata||14.0||35.3||31.8||35.0|
|29.0||Red maple||Acer rubrum||19.7||32.7||32.6||31.0|
|28.9||West African albizia||Albizia ferruginea||21.2||31.4||28.7||34.4|
|28.9||Loblolly Pine||Pinus taeda||14.0||36.2||31.0||34.2|
|28.8||Khasi Pine||Pinus kesiya||13.6||35.9||30.4||35.4|
|28.7||New Guinea Walnut||Dracontomelon mangiferum||18.7||33.5||30.4||32.0|
|28.6||White Meranti||Shorea hypochra||21.8||29.1||30.9||32.7|
|28.6||Pond Pine||Pinus serotina||15.1||35.3||27.6||36.5|
|28.4||Algarrobo Blanco||Prosopis alba||36.0||15.0||20.8||41.9|
|28.4||Oregon White Oak||Quercus garryana||34.8||19.9||23.7||35.3|
|28.1||Black Cherry||Prunus serotina||19.7||29.2||29.6||34.1|
|28.0||Overcup Oak||Quercus lyrata||24.9||27.6||30.4||29.1|
|27.9||Hoop Pine||Araucaria cunninghamii||15.2||34.3||29.6||32.4|
|27.3||Oregon Ash||Fraxinus latifolia||24.3||26.2||30.7||28.2|
|27.3||African Juniper||Juniperus procera||18.4||28.6||27.8||34.4|
|27.2||Common Lime||Tilia x europaea||14.1||34.1||29.8||30.7|
|27.1||Virginia Pine||Pinus virginiana||15.1||29.9||31.5||31.9|
|27.1||Red Elm||Ulmus rubra||17.7||29.2||31.5||30.0|
|27.1||New Zealand kauri||Agathis australis||14.8||34.6||30.3||28.7|
|27.1||Southern Red Oak||Quercus falcata||22.1||29.0||28.8||28.5|
|27.1||Queensland Maple||Flindersia brayleyana||16.7||31.1||28.0||32.5|
|26.9||Black Ash||Fraxinus nigra||17.5||31.8||30.4||27.8|
|26.8||Honduran Mahogany||Swietenia macrophylla||18.6||28.5||27.9||32.2|
|26.6||African Walnut||Lovoa trichilioides||19.4||25.7||29.4||31.8|
|26.5||Paper Birch||Betula papyrifera||18.8||31.6||29.6||26.3|
|26.5||Norfolk Island Pine||Araucaria heterophylla||13.1||34.7||28.0||30.3|
|26.2||Monkey Puzzle||Araucaria araucana||7.7||33.6||34.2||29.4|
|26.2||Western Hemlock||Tsuga heterophylla||10.7||32.5||26.8||34.6|
|26.0||Table Mountain Pine||Pinus pungens||13.3||30.6||27.6||32.6|
|25.9||European alder||Alnus glutinosa||13.1||31.7||32.2||26.7|
|25.8||Yellow Meranti||Shorea spp.||14.2||30.6||27.9||30.5|
|25.7||Sand Pine||Pinus clausa||14.9||27.4||27.6||33.1|
|25.7||Port Orford Cedar||Chamaecyparis lawsoniana||11.8||32.9||29.5||28.4|
|25.6||Cedar of Lebanon||Cedrus libani||16.9||28.6||28.4||28.5|
|25.4||Cape Holly||Ilex mitis||22.8||25.1||25.7||28.1|
|25.2||Abura||Mitragyna ciliata (=Fleroya)||16.9||26.8||28.1||29.2|
|25.2||Huon Pine||Lagarostrobos franklinii||19.1||25.7||26.1||29.8|
|25.1||Bur Oak||Quercus macrocarpa||28.5||18.7||25.7||27.4|
|25.0||Cuban Mahogany||Swietenia mahogani||19.2||26.0||25.3||29.5|
|24.9||Southern Magnolia||Magnolia grandiflora||21.2||27.1||26.5||25.0|
|24.8||Light Red Meranti||Shorea contorta||11.0||33.0||26.5||28.7|
|24.6||Bigleaf maple||Acer macrophyllum||17.5||28.3||25.1||27.7|
|24.6||Radiata Pine||Pinus radiata||14.4||28.5||27.3||28.1|
|24.5||Siberian Elm||Ulmus pumila||20.4||21.4||26.6||29.8|
|24.5||Peruvian Walnut||Juglans neotropica||19.8||20.9||26.4||31.0|
|24.5||Red Pine||Pinus resinosa||11.2||32.5||25.9||28.4|
|24.3||Pumpkin Ash||Fraxinus profunda||20.5||24.1||26.2||26.3|
|24.3||Mountain Hemlock||Tsuga mertensiana||13.8||25.5||27.3||30.4|
|24.2||London plane||Platanus x acerifolia||19.4||24.6||25.5||27.5|
|24.2||Yellow silverballi||Aniba hypoglauca||22.3||25.2||22.4||26.9|
|24.1||Scots Pine||Pinus sylvestris||10.8||28.5||28.9||28.1|
|24.1||American Elm||Ulmus americana||17.0||25.7||28.2||25.3|
|24.0||Grey alder||Alnus incana||15.7||30.4||28.0||21.9|
|23.8||Yellow Cedar||Cupressus nootkatensis||11.6||27.6||26.2||29.7|
|23.5||Pacific silver fir||Abies amabilis||8.3||33.7||23.8||28.3|
|23.4||Yucatan Rosewood||Dalbergia tucurensis||25.4||20.7||23.6||23.8|
|23.3||Pitch Pine||Pinus rigida||12.5||27.8||25.4||27.6|
|23.0||Noble fir||Abies procera||7.9||32.2||25.3||26.5|
|22.9||Japanese Larch||Larix kaempferi||12.0||24.1||27.6||28.0|
|22.9||Spruce Pine||Pinus glabra||14.2||27.2||24.0||26.1|
|22.8||Sweet Chestnut||Castanea sativa||13.7||23.6||24.1||29.9|
|22.8||Austrian Pine||Pinus nigra||13.3||31.1||21.3||25.6|
|22.8||Water Tupelo||Nyssa aquatica||17.9||23.6||22.2||27.5|
|22.7||Yellow poplar||Liriodendron tulipifera||10.7||31.3||23.4||25.4|
|22.7||Sitka Spruce||Picea sitchensis||10.1||31.8||23.6||25.5|
|22.7||Alder-leaf Birch||Betula alnoides||17.0||23.3||20.3||30.2|
|22.5||Patula Pine||Pinus patula||10.9||28.6||27.3||23.3|
|22.5||Fijian kauri||Agathis macrophylla||17.3||27.6||19.5||25.7|
|22.5||Northern Silky Oak||Cardwellia sublimis||17.3||24.6||21.8||26.2|
|22.4||East Indian Kauri||Agathis dammara||12.2||25.9||22.4||29.3|
|22.1||Spanish Cedar||Cedrela odorata||12.0||25.3||23.9||27.2|
|22.1||Black Spruce||Picea mariana||10.3||30.0||23.4||24.7|
|22.0||Red alder||Alnus rubra||11.8||26.7||22.6||27.0|
|22.0||Australian Red Cedar||Toona ciliata||14.3||25.6||24.2||23.8|
|21.9||California red fir||Abies magnifica||9.8||29.1||24.2||24.7|
|21.9||Monterey Cypress||Cupressus macrocarpa||12.4||20.9||28.1||26.4|
|21.9||Southern Silky Oak||Grevillea robusta||18.2||21.3||25.3||22.8|
|21.8||White fir||Abies concolor||9.4||29.1||22.3||26.5|
|21.8||Staghorn Sumac||Rhus typhina||13.8||22.2||23.7||27.6|
|21.6||Southern Redcedar||Juniperus silicicola||12.2||21.7||21.5||31.1|
|21.6||Cascara Buckthorn||Rhamnus purshiana||21.6||16.8||19.5||28.4|
|21.6||Jack Pine||Pinus banksiana||11.4||26.0||22.9||26.1|
|21.5||Mexican Cypress||Cupressus lusitanica||9.9||23.9||26.2||26.0|
|21.5||Pinyon Pine||Pinus edulis||17.7||21.0||17.0||30.2|
|21.3||Black Tupelo||Nyssa sylvatica||16.4||22.2||21.8||25.0|
|21.3||California Black Oak||Quercus kelloggii||22.7||17.3||19.3||26.0|
|21.0||Red Spruce||Picea rubens||9.6||30.9||22.0||21.7|
|20.7||Grand fir||Abies grandis||9.6||30.2||19.6||23.6|
|20.7||Horse chestnut||Aesculus hippocastanum||16.7||18.6||22.5||25.0|
|20.4||Maritime Pine||Pinus pinaster||7.4||23.3||24.8||26.1|
|20.4||Western White Pine||Pinus monticola||8.1||28.5||22.3||22.7|
|20.4||Eastern Red Cedar||Juniperus virginiana||18.6||15.0||19.8||28.1|
|20.3||Gray Birch||Betula populifolia||15.5||21.3||22.6||21.7|
|20.3||Lodgepole Pine||Pinus contorta||9.4||25.7||21.5||24.5|
|20.3||Giant Chinkapin||Chrysolepis chrysophylla||14.9||23.4||25.1||17.7|
|20.2||Dutch Elm||Ulmus x hollandica||17.6||19.9||23.0||20.4|
|20.2||Bigtooth Aspen||Populus grandidentata||8.1||27.8||20.6||24.1|
|20.0||Okoume / Gaboon||Aucoumea klaineana||7.7||23.1||25.6||23.8|
|19.9||Jeffrey Pine||Pinus jeffreyi||9.8||23.4||21.2||25.4|
|19.9||Leyland Cypress||Cupressus x leylandii||8.2||17.5||28.7||25.3|
|19.8||Ponderosa Pine||Pinus ponderosa||9.0||24.6||21.5||24.2|
|19.7||Silver maple||Acer saccharinum||14.2||21.0||20.1||23.6|
|19.6||Queensland kauri||Agathis robusta||11.2||20.8||21.1||25.3|
|19.6||Norway Spruce||Picea abies||7.2||27.3||20.7||23.3|
|19.5||European silver fir||Abies alba||5.9||22.4||22.0||27.7|
|19.5||European Aspen||Populus tremula||7.2||27.4||20.3||22.8|
|19.4||English Elm||Ulmus procera||16.7||18.5||21.5||21.0|
|19.3||American Chestnut||Castanea dentata||10.7||23.1||19.2||24.2|
|19.3||Eastern Hemlock||Tsuga canadensis||9.8||22.4||20.1||24.7|
|19.2||Balsam fir||Abies balsamea||7.7||26.8||19.8||22.4|
|18.9||Eastern Cottonwood||Populus deltoides||8.3||26.4||19.0||21.9|
|18.7||White Spruce||Picea glauca||9.4||25.1||19.4||20.9|
|18.7||Limber Pine||Pinus flexilis||8.3||21.7||20.6||24.0|
|18.6||Engelmann Spruce||Picea engelmannii||7.4||26.4||20.4||20.0|
|18.4||Pin Cherry||Prunus pensylvanica||10.1||24.1||19.0||20.3|
|18.2||Subalpine fir||Abies lasiocarpa||6.6||25.3||18.7||22.0|
|18.1||Black Poplar||Populus nigra||8.9||18.8||21.0||23.6|
|17.9||Mexican alder||Alnus jorullensis||12.8||20.9||18.5||19.2|
|17.8||Eastern White Pine||Pinus strobus||7.2||23.4||19.2||21.3|
|17.5||Crack Willow||Salix fragilis||12.8||21.3||21.5||14.3|
|17.3||Black Cottonwood||Populus trichocarpa||6.6||24.1||19.0||19.7|
|17.3||Incense Cedar||Calocedrus decurrens||9.2||18.7||17.6||23.5|
|16.9||Nepalese alder||Alnus nepalensis||7.2||22.4||15.9||21.9|
|16.8||Indian pulai||Alstonia scholaris*||8.1||22.9||17.7||18.4|
|16.8||Sugar Pine||Pinus lambertiana||7.2||22.2||18.1||19.4|
|16.6||White Willow||Salix alba||11.3||20.7||18.0||16.3|
|16.4||Quaking Aspen||Populus tremuloides||6.6||22.0||18.7||18.3|
|16.3||Alligator Juniper||Juniperus deppeana||24.3||9.6||13.9||17.6|
|16.3||Northern Catalpa||Catalpa speciosa||10.9||22.7||21.5||9.9|
|16.0||Cheesewood, emien||Alstonia congensis (and A. boonei)||7.9||19.9||17.1||19.1|
|15.8||Andean alder||Alnus acuminata||8.3||20.9||16.0||18.0|
|15.8||Western Red Cedar||Thuja plicata||6.6||20.3||16.2||20.0|
|15.7||Siam balsa||Alstonia spatulata||8.8||18.7||15.7||19.5|
|15.6||Yellow buckeye||Aesculus flava (octandra)||6.6||21.7||16.2||17.8|
|15.2||Black Willow||Salix nigra||8.3||18.0||17.0||17.4|
|14.4||Atlantic White Cedar||Chamaecyparis thyoides||6.6||16.1||14.2||20.8|
|14.2||Balsam Poplar||Populus balsamifera||5.5||20.1||14.2||17.0|
|13.6||Gowen Cypress||Cupressus goveniana||11.3||9.7||18.3||15.1|
|12.3||Northern White Cedar||Thuja occidentalis||5.9||13.1||13.4||16.7|
My interpretation of the data
95.3*—The World’s Strongest Wood (with a great big asterisk)
With an astounding strength index of 95.3, pintobortri (Pouteria eugenifolia) earns the top spot among all woods. But I am not quite ready to hand over the top spot to this species without reservation.
While the estimated hardness is one caveat, the biggest issue I have with this wood is simply that it’s so obscure and not thoroughly studied. All the data is based upon a single source, so there’s no averaging or balancing to serve as a moderating force. You may be wondering, in practice, how often does one set of data on a wood species come in stark contrast to another dataset? All the time.
Let me present one such instance. Pintobortri’s best-in-class measurement of MOR at 37,560 lbf/in2 (259.0 MPa) is nearly identical to an African hardwood named congotali (Letestua durissima), which, according to one source, measures in at an impressive 37,270 lbf/in2 (257.0 MPa). The only difference is that congotali has more data points available (with lower values), which serves to paint a more reasonable, less extreme version of its strength properties. This is a phenomenon that I discuss at length in the video, Quest for the Hardest Wood in the World.
Honorable mention: There are a few other Pouteria species, most of which are probably just as obscure and unobtainable as P. eugenifolia, which have a very high strength index. Not wanting to clutter the list with completely unknown woods that are more-or-less repeats, I’ve only listed the highest-scoring member of the group. Notable runner-ups include asepoko (P. guianensis) with a strength index of 79.2, and P. egregia at 71.0.
80.3—The World’s Strongest Wood (without an asterisk)
With a scarcity of data in the top positions (especially Janka hardness data) we have to move a few notches down the list before landing on a wood without any sort of footnote or caveat attached to it. There, free from any dark clouds of doubt, we find kaneelhart (Licaria canella), with a very respectable strength index of 80.3. Each of its values are documented and accounted for, and come from multiple sources.
It’s worth noting that kaneelhart’s strength index is pulled down significantly by its somewhat subpar Janka hardness, so if it’s simply raw structural strength and rigidity that’s in question, kaneelhart certainly ranks very near the very top of the heap, even when other lesser-documented and asterisk-laden woods are included in the mix.
But another pertinent note to all the realists out there is that all of the wood species in the top three or four spots aren’t generally exported on a regular basis, and can be (very) hard to come by. However, the IUCN reports that each of the species in these top spots are listed as being of “least concern” with regards to extinction, with stable population trends.
Honorable mention: Greenheart, sitting at a strength index of 68.8, is another wood with outstanding structural strength properties that’s brought down somewhat by it’s disproportionately low (yet still very good!) Janka hardness value.
79.8—The World’s Strongest Wood (you can actually buy)
Heretofore, nearly all woods at the top of this strength list have ranged in availability from challenging (kaneelhart) to nearly impossible (pintobortri). Yet still very high on the list is snakewood, sitting at a strength index of 79.8. Snakewood is an exotic hardwood that can still be found with a simple ebay search or a trip to a local specialty hardwood supplier (especially if they feature turning blanks or knife scales for hobbyist-oriented woodworkers).
Like all the woods listed above, there are caveats. The biggest in my mind is that the tree that yields snakewood is typically very small, and usually full of defects. So while snakewood is one of the strongest woods you’ll probably ever have in your possession, chances are that any pieces will be so small (not to mention expensive), the point will be moot. This is definitely not a structural timber—it’s far more often admired for it’s striking grain patterns and colors.
Honorable mention: With a strength index of 78.1, katalox is another wood with decent commercial availability. It’s certainly available in larger sizes than snakewood, though there tends to be large amounts of sapwood, so wastage can be high.
70.4—The World’s Strongest Wood (you can actually use for its strength)
After filtering out woods for lack of availability, the next sieve that contenders must pass through is that of usable size. This is where our previous entrant, snakewood, falls short. When it comes to woods that are both commercially available and also found in respectable sizes, what rises to the top of the heap is ipe, with a strength index of 70.4. And closely allied to size is also affordability. It’s simple math: if a tree is large enough to be commercially viable, the wood is usually also less expensive when compared to other smaller, more specialty-oriented hardwoods such as snakewood.
Ipe is commonly used for decking and other exterior applications where durability and good weathering characteristics are required. The only caveat when using this wood for its strength is to use mechanical fasteners—especially when joining pieces of the wood that are intended to be outside in the elements. Ipe is notoriously difficult to glue (or at least, to remain glued together) in exterior applications.
Honorable mention: Close behind is bulletwood and cumaru, both more or less tied at 69.8. Both of these woods can be found at flooring or decking dealers, and larger structural pieces are also not unheard of. In addition, all three of these woods have the added benefit of being highly rot resistant (but also troublesome in gluing!).
47.5—The World’s Strongest Wood (you might have in your backyard)
Statistically speaking, only about two thirds of those reading this will be from the United States or Canada, so my apologies to the remaining third for which this entry will seem out of place. You may have noticed that all the previous top positions have belonged to tropical hardwoods, so my goal with this category is to list a temperate species that readers might be familiar with—perhaps even in tree form. For this title, many hickory species hover near the top, but it is pignut hickory that statistically comes out the winner with a strength index of 47.5.
It’s true that there are other North American species with higher values, such as black ironwood or Texas ebony, but these species only occur at the very southernmost tips of the United States, with their natural distributions being centered in much hotter climates—hardly what I would consider temperate-zone species. But many hickories (including pignut) are found firmly in the midst of the eastern United States, and even have a sprinkling of distribution northward into Canada as well. In these areas, hickory has a reputation as being one of the toughest woods around, and it’s well founded.
Honorable mention: It’s hard to believe that hickory beats out so many other worthy competitors found in America, but when multiple facets of wood strength are considered, pignut hickory tops even respectable hardwoods such as osage orange, black locust, hornbeam and hop-hornbeam. But when temperate European species are throw into the mix, the title goes to the freakishly strong iron birch (Betula schmidtii), with a strength index of 65.7. But its MOR index is an astounding, must-be-a-typo value of 89.6! (Another runner-up mention goes to Cornelian cherry (Cornus mas), reputed by Europeans in the ancient world to be one of the absolute strongest woods around, there’s unfortunately no studies or reputable data available on this wood to verify the claim.)
Sidenote: composite woods and other manmade materials
When a woodworker is looking at wood for strength purposes, a natural comparison might be to that of composite wood materials—basically, anything that combines some form of wood material with glues, binders, or other synthetic materials. The important thing to remember is this: what makes wood such a special material lies in its grain. The more a product takes advantage of the wood grain, the better it will perform.
There are two primary types of composite materials pertaining to strength wood grain.
- Panel products that don’t fully leverage wood grain strength (instead emphasizing convenience and dimensional stability)
- Laminated products that have a specific long axis of wood fibers, and therefore a specific axis of strength
First, let’s take a look at the data to have a point of reference. Most of these composite materials can be highly variable depending on which wood species they are derived from (such as plywood). Also, data for Janka hardness and crushing strength was lacking, so it is only a partial picture. Nonetheless, the averages of known values are presented in the chart below, and help to give a general picture to compare these products to solid wood.
|30.9||LVL (laminated veneer lumber)||42.2||19.5|
|23.9||Glulam (glued-laminated timber)||34.1||13.7|
|11.6||OSB (oriented strand board)||14.0||9.2|
|5.4||MDF (medium density fiberboard)||4.2||6.5|
Referring back to the two types of composite materials, those lacking wood fiber/grain, and those leveraging wood grain, a spectrum can be formed:
- 1.6-11.0—Hardboard, particleboard, and MDF Composed with little to no true wood grain, instead using synthetic materials in combination with wood flour. The overall strength properties and screw-holding abilities are abysmal, as reflected by the strength index going as low as 1.6 for particleboard. However, the material tends to be rather hard and stable, providing a good substrate for veneer. Also, while strength properties are low, they are more or less equal in all directions.
- 11.6-12.6—Plywood and OSB Composed of larger pieces (or sheets) of wood with fibers intact, but with alternating or random grain directionality. Slightly better modulus of elasticity, and much better screw holding ability, reflected by the slightly higher strength index going up to an average of 12.6 for plywood. Still not up to the task of supporting long stretches of load alone, such as bookshelves.
- 23.9-30.9—LVL and glulam Composed of larger pieces of wood with fibers intact and oriented along the same axis—the closest thing to solid wood. Because of the multiple laminations of wood, the effects of knots and other defects are minimized, and the layers of glue also contribute an appreciable amount of stiffness. LVL scores a 30.9 strength index, a lot of that coming from the very good MOE. Understandably very good at handling loads across longer spans.
LVL has been described as being even stronger than solid wood, a claim that is both true, but also must be qualified. LVL will generally be stronger than the source wood from which it is made—this is usually a construction wood like pine. Thus, in the search for the strongest wood in the world, composite products can only go so far, and while providing consistency and predictably, they are far from the top of the list.
But what about…
In lists like these, there are inevitable objections or interjections of “but what about…” I think if you take a look at the list above, you’ll find it very comprehensive. If there is a species missing, it’s because there was a lack of data in at least on of the primary strength categories.
I’m always open to new suggestions, but after searching through the literature I have available, what you see above is just about everything I have. If you have a suggestion, please include a source of data data with strength properties so I can give it a fair evaluation.
so i make a lot of wooden swords, and i always strive towards more durable designs, what is the best hardwood for a sword blade?, i always had problems with splintering Ash and White Oak blades, but i recently tried Ipe, which seems a lot better, might there be any other hardwood that is great against blows from other wooden swords across the grain?
Kind Regards, Amér from Denmark
Where can I find references to mor of iron birch?
Since wood densities can very dramatically, it might be beneficial to include a tidbit about strength to weight ratio. In making baseball bats, I’ve noticed that birch performs better than ash at the same densities when it comes to wood bat durability even though their average density is different on the site.
Super thankful for this article, I was wondering if you had a reference for the highest strength to weight ratio on these woods?
Which type of strength would be most applicable to the ability to hold a screw and resist tearout?
I would say a combination of Janka hardness and MOR, with MOR being more important.
Fascinating read! I make skinners out of the hardest woods in the world to cut off waste paper from parent rolls at the paper mill I work at. I have made them out of Lignum Vitae, Snakewood, Quebracho, Black Ironwood, African Blackwood, Kingwood & the last one I’m working on Pink Gidgee. Only the hardest woods will work because there’s a lot of force involved while cutting through the paper. These rolls are around 131” and are converted into toilet paper, toweling & napkins. I’ve broken lesser woods over the years right up to Vera wood. So as a tool… Read more »
I expected/wanted to see Tzalam in there. It’s not Cumarú or Ipe but it’s pretty solid, used in flooring, etc.
Have you considered impact strength? Some types of wood like Lignum Vitae or black ironwood which are very strong in static bending or compression tend to break more readily in impact applications compared to weaker woods like ash or hickory. See the following US Forest Products Labratory study comparing impact strengths of various American wood species: https://naldc.nal.usda.gov/download/CAT86200473/PDF Keep in mind the difference between “work to proportional limit” and “height of drop causing failure”: Work to proportional limit is how much energy is needed to make the piece of wood start to fail Height of drop causing failure is how much… Read more »
Thanks, I’m aware of impact strength. The USDA has a LOT of mechanical data on domestic woods, but when you broaden that out to a worldwide scope, the number of different tests becomes much more limited. (Hence the “big three” that I chose above.)
In Australia there has been extensive testing of the local timbers with regards to the impact value (called Izod value) for timbers. A complicating factor is how the impact value changes with seasoning, Some timbers decline in value, others increase. Spotted gums (used for tool handles) values are 20 Joules (J) unseasoned 24 when seasoned. Grey Ironbarks values are 24 J unseasoned to 27 J when seasoned. Some of the Wattles also exhibit increased impact strength, Black Wattle is 39 J! Radiata Pine a local non-native species has decreasing impact strength: 12 J unseasoned and 6.9 J when seasoned. Grey… Read more »
You have Katalox right up there with snakewood and is available in much better sizes. I do not see Camelnut and though I have seen photos of the trees, I have not seen the woods. An arrangement by color might be interesting as example Wenge, Katalox, and Gabon ebony.
Do you mean camelthorn? Or do you have a scientific name for camelnut?
Sorry I was thinking camelthorn. Many videos of trees I believe they said were Camelthorn along the dry riverbeds in Namibia that looked very substantial but of course, were in the National Park there, but watching I get the same feeling I got watching Capt. Nemo fighting the Giant Squid. It is supposed to be scary, But I am looking and thinking “mmm Steaks!”
Fantastic work! I was entralled and then exuberated to find that my whole reason coming to this site was to see if my felled Pignut Hickory Tree was worth the tool wear to incorporate into some of my black cherry and Red Maple projects. Turns out it owns a category. I’m now decided. Thank you.