Janka Hardness

The Janka hardness test is used to determine the strength of wood by measuring the resistance to denting and wear. The test method was developed by Gabriel Janka in 1906 and measures the force needed to embed a 11.28mm steel ball haft its depth into the sample of wood. In 1927 the American Society for Testing and Materials standardized the method and utilize it in both ASTM D1037 and ASTM D143 tests, which determines the strength and durability of wood flooring and lumber. The Janka rating not only dictates a woods durability, but also how easy it can be milled and nailed into.

The higher the Janka rating number, the stronger the wood. One of the highest wood flooring species would be Brazilian walnut with a Janka rating of 3680. Common species like white oak has a rating of 1360, hard maple has a rating of 1450, and cedar flooring has a rating of 900.

Different factors can impact a Janka rating, including where and how the wood sample is cut. Wood cut from different parts of a tree or with different grain directions can produce different results, even if it is the same species. Another variable is what country is stating the result. In the United States a Janka result is displayed in pounds force, whereas in Sweden it is displayed in kilograms force, and in Australia it is displayed in Newtons. These factors can cause some confusion with the final rating result.


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