Learn About Hardwood

Janka Hardness

The industrial standard Janka Hardness Test measures the wood plank’s hardness of the wood species. The hardness of the wood is an important aspect when choosing wood flooring, depending on the use of a space, certain species will be more suitable.

Janka’s standard procedure tests the wood planks’ hardness by measuring the force required to embed a 0.444 in diameter steel ball perpendicularly to the plank, or to the side of the plank. The higher the rating, the harder the wood species is. Additionally, different manufacturers have some slight modifications to the test, therefore the Janka hardness is not an absolute test of the wood’s hardness, but offers a comparative view of different wood species.


Dimensional Stability

Wood stability refers to how much an installed wood floor expands and contracts in relationship to the environmental changes such as moisture or temperature. In other words, all wood change in sizes (shrink or swell) under certain conditions and the minimal changes (lower number on the scale) indicate higher dimensional stability. This numbers in comparison will give a picture which species more resist to impacts of water. Knowing of this is important when hardwood floor will be installed in the places with potentially higher moisture conditions. Species with higher resistance will suit better in this case. It does not necessarily means that water will not damage them, but resistance to the impact of water will be higher.

In an effort to compare stability between species, the numeric values in the chart below represent the percentage of tangential shrinkage from green to over-dry moisture content. Tangential change values normally will reflect changes in plain-sawn wood. Quarter-sawn wood usually will be more dimensionally stable than plain-sawn. Actual percentage change on completed job sites will be significantly less as proximity from board to board will restrain movement. Note this means the higher the percentage the more unstable the wood.


Learn About Hardwood
Article Name
Learn About Hardwood
Standard Janka Hardness Test measures the wood plank's hardness of the wood species.
Publisher Name
FERMA Flooring
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