Janka hardness is a standardised test showing how well a wood species resists denting and wear. The higher the Janka value, the harder and more wear-resistant the wood. It is named after the researcher Gabriel Janka, who developed the method in the early twentieth century.
How it is measured
In the Janka test a steel ball 11.28 mm in diameter is pressed into the wood until exactly half the ball (its equator) is embedded. The force needed is the Janka value, given in newtons (N) or pound-force (lbf). Because wood behaves differently along and across the grain, testing follows a fixed standard, usually on the end or radial face.
For orientation: soft conifers such as spruce and pine score low, oak sits in the middle, and tropical hardwoods such as ipê and azobé score very high. The ranking matters more than the exact number — it makes species directly comparable.
Application
Janka hardness is most useful when choosing wood that takes a beating: floors, stair treads, decking boards and worktops. For a living-room floor you would pick a harder species than for panelling that is never walked on.
Points to note
- A high Janka value means dent resistance, not automatically moisture resistance or outdoor durability
- Combine it with data on stability and rot resistance for exterior choices
Related terms
- Wood species
- Hardwood
- Spruce wood
- Material hardness
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