Locust Wood Strength (& Is It a Hardwood or a Softwood?)

Is Locust a Hardwood or a Softwood? (& Is It Strong?)

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This article will discuss one of the most durable and strong tree species that grows naturally in North America, the Locust.

If you don’t know much about Locust timber, this article outlines what type of wood Locust is, its different strength values, and everything else you need to know.

Is Locust a Hardwood or a Softwood?

Black locust is a hardwood. The grain is coarse, the heartwood is yellow-brown, and the sapwood is white. With age, the heartwood will darken. There are two types of tree referred to commonly as ‘locust’ – the black locust and the honey locust. Today’s article will focus on the black locust.

European woodworkers were the first to start referring to trees as hardwood and softwood. Native European deciduous trees are usually stronger and more durable compared to European evergreen trees. European evergreen pines and conifers grow fast, making them generally less strong and dense. Because of these differences, with time, deciduous trees were referred to as hardwoods, and pines were termed softwood.

The terms softwood and hardwood aren’t particularly helpful when describing timber. This is because some softwoods are stronger than other hardwoods. As an example, spruce is denser than some hardwoods, such as beech, balsa, and aspen. Balsa is termed a hardwood, but it’s softer and weaker than most commercial softwoods.

Locust Wood Strength: All You Need to Know

To properly understand the qualities of a timber, there are several tests a piece of wood can be put through. With this handful of tests, the exact strengths and weaknesses of the wood can be outlined. In this section, we’ll outline how Locust wood performs for compressive strength, bending strength (modulus of rupture), stiffness (modulus of elasticity), hardness (Janka scale), and density.

Compressive Strength

Locust wood has a crushing strength of 10,200 lbf/in2 (70.3 MPa). Compressive strength can also be called crushing strength. To calculate this value, pressure is applied to the wood piece from both ends, going inwards. Incrementally, more force is applied until the wood fails. If you are about to undertake a woodworking project where the timber will be under compressive strength, such as deck posts or chair legs, the data from this test is very helpful.

Compared to other timbers, locust’s compressive strength is stronger than white oak, at 7,440 lbf/in2 (51.3 MPa), and redwood at 5,690 lbf/in2 (39.2 MPa). Ipe, on the other hand, is stronger than locust, with a  score of 13,510 lbf/in2 (93.1 MPa).

Bending Strength (Modulus of Rupture)

Locust wood has a bending strength of 19,400 lbf/in2 (133.8 MPa). The modulus of rupture is more commonly called bending strength. This test determines how far a tree species will bend before rupturing. To conduct a bending strength test, a piece of timber is supported from both ends, with pressure applied in the middle of the timber where there is no support. Pressure is increased incrementally until the timber cannot bend anymore and ruptures.

Compared to other tree species like hickory and red oak, locust wood is weaker. However, these two are known for being very strong, so this shouldn’t come as a surprise. Hickory has a bending strength of 20,200 lbf/in2 (139.3 MPa), and red oak has a bending strength of 20,200 lbf/in2 (139.3 MPa).

Stiffness (Modulus of Elasticity)

Locust wood has a stiffness of 2,050,000 lbf/in2 (14.14 GPa). Stiffness can sometimes be quite technical to describe. In simple terms, the stiffness test evaluates how much a piece of wood changes when force is applied to it. To conduct the test, the wood is supported at both ends, with pressure then applied in the middle.

The amount the wood deforms under this pressure is then measured. Depending on the wood’s moisture content, its stiffness will change, so unless otherwise stated, the test is conducted with 12% moisture content.

Locust wood is stiffer than red oak, which has a stiffness of 1,820,000 lbf/in2 (12.50 GPa). However, it is weaker than hickory, which has a stiffness of 2,160,000 lbf/in2 (14.90 GPa).

Hardness (Janka Scale)

Locust wood has a hardness of 1,700 lbf (7,560 N). Out of all the tests, the knowledge gained from the Janka hardness is one of the easiest to apply. This tells you how easily a type of timber will dent, ding, bruise, and generally wear down. You can also work out how difficult a timber will be to nail, screw, sand, and saw by how high its Janka score is. The actual Janka test measures how much force is needed to push half of a .444” diameter steel ball into the piece of wood.

Comparing locust’s Janka score to other species, we can see that it is harder than many timbers. For example, white oak has a Janka hardness of 1,350 lbf (5,990 N) and basswood has a hardness of around 410 lbf (1,820 N).


Locust wood has a density of 44 lbs/ft3 (700 kg/m3). As a general rule, the denser a tree species is, the stronger and heavier it will be.

Locust wood is much denser than western cedar, which has a density of 22 lbs/ft3. White oak is relatively similar to locust wood, with a density of 47 lbs/ft3.

Is Locust Strong?

Black locust is considered a very strong hardwood. Out of all the trees that are domestically grown in the U.S., only hickory is stronger. However, locust is also very stable and resistant to rot, fungus, and pests. These qualities make it great for outdoor uses such as fencing and decks.

It’s important to remember that the strength of a piece of wood is largely determined by the type of tree it is. However, each component must be assessed in person because defects such as shakes, splits, knots, and checks will reduce the strength of the board. Alongside this, pests will also dramatically reduce the overall strength of the wood.


Locust wood is an extremely tough, durable, and weather-resistant hardwood. As one of the strongest domestic timbers in the US, it’s used for a wide range of projects. The weather-resistant qualities black locust possesses lend themselves very well to outdoor uses.

However, it can also be used for cabinetry and furniture because the wood has some beautiful colorings. On top of this, locust wood grows very quickly and lives for a long time – both of these attributes make it appealing to foresters as a sustainable alternative to more widely used timbers.