Named after Austrian wood researcher Gabriel Janka, the Janka Hardness Scale is utilized to determine the relative hardness of an exotic or domestic species. This test measures the amount of force required to embed a 0.444″ steel ball into the piece of wood to half of its diameter. Wooden materials that have a higher Janka rating are harder than woods with a lower Janka rating.
Essentially, this test measures the resistance of wood against dents and wear, as well as determines its overall hardness compared to other wooden materials. For testing, a 6-inch wooden sample is required that is 2-inches wide by 2-inches thick.
One of the most common uses for the Janka hardness test is to determine whether or not a wooden species is suitable for use as flooring. There are a few additional factors that affect how flooring performs on the test, however, including: the type of core for engineered flooring such as HDF, oak, pine, birch, poplar; grain direction; floor wear surface; and thickness.
This innovative hardness test was developed over 100 years ago, in 1906. In the late 1920s, the test would go on to be officially standardized by the American Society for Testing and Materials (ASTM).
Force is the resulting measure of the Janka Hardness Test and — in the United States — is represented by pounds-force (lbf).
= 1lb X Gn
= 1lb X 9.80665 m/S2 / 0.3046 m/ft
= 1lb X 32.174049 ft/Sq
= 32.174049 ft-lb/S2
Red Oak is currently the industry mean for hardness, meaning at 1,290 lbf. For perspective, Douglas Fir, a softer wood, measures at 660 lbf, while a harder wooden material like Brazilian Cherry measures at 2,350 lbf.
The Janka Hardness Test is a great hardness benchmark for flooring for both residential and commercial structures. It’s important to keep in mind, however, all wood, regardless of hardness, will wear, tear, and dent over time with enough consistent impact.