Janka hardness scale, Floor Coverings International OahuDeciding to install hardwood floors in your house is one of the smartest things you can do if you want to instantly improve the look of your home and increase its resale value. Hardwood floors are a timeless flooring option that will match with nearly any décor, from stylish modernity with bamboo, to cozy traditionalism with northern red oak. But choosing what type of wood you want can be overwhelming as a layman, with so many species available that all have such different characteristics. Floor Coverings International of Oahu and Honolulu has put together this post in order to explain one of the ways in which you can determine the quality of the species of wood you will use for your hardwood floors. The Janka hardness test is one of the premier ways in which wood species are measured for flooring quality, so it is excellent information to have as you begin your flooring adventure.

What is the Janka Hardness Test?

The Janka hardness test is the industry standard by which the hardness of hardwood is determined. The quality of a wood species is not the only determining factor when it comes to the quality of the wood, but ability to resist indentation is certainly a good thing for your floor to have, and that is what the Janka test measures. The Janka test will determine which hardwoods are suitable to be used as flooring materials. On the Janka scale, the higher the Janka score, the harder the wood. Janka ratings also give an indication of how workable a wood species is, with harder hardwoods being more difficult to nail and saw.

How Is A Janka Score Determined?

In order to measure a wood species’ ability to resist indentation, the Janka scale measures hardness as how much force it takes to mar the wood. This is done by taking a .444 inch (11.28 mm) ball made of steel, and dropping it onto the surface of a wood plank from the species in question. However much force is needed to embed the steel ball halfway into the wood is what is used as the final Janka score. So northern red oak, which is used as the industry’s standard measuring stick, has a Janka score of 1290, meaning it takes 1290 pounds of force in order for half of the steel ball to embed in the wood. Wood grain direction can also affect hardness, so testing on the plank’s surface is known as ‘side hardness,’ while testing done on a stump where the wood is cut is known as ‘end hardness.’

Issues with the Janka Hardness Test

It is important to remember that the Janka score is not the be all and end all way of determining a wood species’ quality. It merely measures a wood’s hardness, and while resisting indentation is good, super hardwoods can be very difficult to work with. Other ways of determining a wood’s quality include modulus of elasticity for example, which measures a wood’s ability to return to its original shape after being bent. Some exotic hardwoods with very high Janka scores will simply break, while a softer wood like Douglas fir will perform quite well. Other things to consider are impact bending, tensile strength, and dimensional stability. Another issue is that the units of measurement are not standardized, so while the US measures force in pounds, other countries use kilograms or newtons to determine force. In general, it is important to remember that Janka score is good information to have, but shouldn’t be the deciding factor in what species of wood you choose for your hardwood flooring.

Types of Hardwoods and their Janka Scores

The hardest wood species are usually exotic hardwoods from places like South America or other regions with similar climates. The hardest wood in the world though, comes from Australia. The Australian Buloke has a Janka hardness rating of 5060. Other species with very high Janka scores include Patagonian Rosewood at 3840, Brazilian Walnut at 3684, Cumaru at 3540, Ebony at 3220, and non-carbonized stranded bamboo at 3000. Compare these to the most popular flooring species, red oak, which has a Janka score of 1290. Most domestic woods reside in this range on the Janka scale, with Ash at 1320, Beech at 1300, Yellow Birch at 1230, and Larch at 1200. Most softwoods, or gymnosperms (trees with naked seeds or pine cones rather than fruit or nuts) tend to be on the lower end of the Janka scale, with Douglas fir at 660, Southern Yellow Pine at 870, Juniper at 626, and Larch at 590. The woods with the lowest Janka scales, such as Balsa at 100, are not used for flooring. Whether you want an exotic super hardwood, or a softer domestic gymnosperm wood, be sure to call Floor Coverings International of Oahu and Honolulu for a free, in-home consultation!

Photo by Kunal Mehta