When in doubt about the type of wood to select for your cabinetry, flooring, furniture or millwork project, refer to the Janka Rating System, which measures the relative hardness of woods.
The hardest commercially available domestic hardwood is hickory; it is five times harder than aspen, one of the “soft” hardwoods. And while this example lists just some of the most popular hardwood species, there are hundreds of varieties, representing the North American hardwood population.
Because hardness is an important factor, and hardness varies for each species, the Janka Scale of Hardness is an excellent tool to help identify appropriate choices.
So what does the Janka test consist of? The process of measuring the density of wood begins by embedding a steel ball that has a diameter of 11.28 millimeters (roughly 0.444 inches) halfway into the wood’s surface. The force required to push the ball into the wood (measured in pounds-force, or lbf) indicates how dense and strong the wood is. For example, hickory hardwood has a Janka rating of 1820; this means that it required 1,820 pounds of force to embed the steel ball into hickory’s surface.
The hardness and density of wood is often determined by the direction of its grain. Measuring a wood’s flat or horizontal grain (face) is the most general way to determine its hardness. Although vertical wood grain (edge) is tested, the results are not displayed on the Janka Hardness Scale. The results shown on the Janka Hardness Chart indicate the hardness of a wood’s face, and not its edges (or “side hardness”).
Species Comparative Janka Ratings (click to download pdf)
This should only be used as a general guide when comparing various species of wood flooring. Depending on where the wood is harvested the results may vary. Plank construction and finish are also important factors when determining the durability and ease of maintenance of any wood floor.
The majority of hardwoods and many softwoods are durable enough to withstand normal flooring use – especially with proper installation and finishing. However, it is important to note that no matter the Janka rating, all wood will dent or mar with a hard enough impact.
