In 1906, Gabriel Janka, an Austrian wood researcher was inspired about finding and rating of wood hardness. He invented a scale to measure and compare the hardness of wood. Since then, it is known as Janka scale or Janka rating.
The Janka rating that’s being used by North American Wood industry, has been standardized by ASTM (American Society for Testing and Materials).
Let’s first review the scale and then discuss how it impacts your flooring selection.
The Janka Scale:
Understanding the scale or rating:
The number we refer on Janka scale is the force in lbs. This number is the force required to insert a small steel ball in to the wood. The ball is embedded half of its diameter in to the wood face. The higher the force, higher is the hardness.
The Janka number is the pounds of force (LbF) required to create 200 sq mm of indentation on the wood surface using a 0.444-inch steel ball. So, Red Oak at 1290 on the scale indicates the average force required for Red Oak is 1290 Lb.
What is a good Janka hardness for hardwood floor?
Any wood with a Janka rating of 900 or up is a good hardwood for flooring. Red Oak with 1290 on scale. And it is the most common and popular one.
You can find stronger hardwood with a hardness of 2400 lbs or more. For example, Brazilian Cherry is 2820. But, do you really need that much hardness for your flooring? May be not. The standard one is Oak (Red Oak 1290 and White Oak 1360) with an optimum hardness.
Can we modify the hardness of wood floor?
Wood is a natural product. No manufacturer can change or modify the hardness. But they can definitely improve the functionality. For example, the hardness or stability depends upon the way the log is cut. Rift sawn and quarter sawn wood is more stable compared to plain sawn one.
It is the grain pattern and stability which puts Quarter sawn and Rift sawn to the upgrade cadre. These two special sawing techniques help reduce twisting, cupping and warping. Also, Quarter sawn and Rift sawn wood floors are very good in resisting moisture penetration.
Another factor is moisture content. Moisture content and hardness are related and less moisture makes the wood harder. Although, there is always a term called “optimum”. So, it should be optimum moisture and not minimum moisture to make the wood hard or tough! The moisture content at normal acceptable conditions is usually 6 to 8 %.
Is hardest wood the best wood?
Yes, the hardest wood is best for flooring. But may not be the best for your pocket! The harder the wood, the more difficult is to work with. And so, hardest is not always the best.
Australian Buloke is one of the hardest woods with 5060 lbf on Janka scale. This is about 5 times more than the Oak, that we consider a good flooring! Obviously, the hardest woods are dense and so their engineering properties are greater.
The hardest woods are great looking, scratch resistant, water resistant and long lasting. But they are rare and costly. Also, the cutting and nailing is very difficult which make them less preferred ones from installation point of view.
Hope the details helped you understand “What is a good Janka hardness for hardwood floor”. For more on hardwood and flooring please see below suggested readings.
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