Rating the Hardness of Hardwood Flooring
26th October 2017
How do you determine the hardness and durability of hardwood flooring, and how do you compare one wood species to another in regards to hardness when choosing a flooring product?
The answer is the Janka hardness test.
How Hard is a Hardwood Floor
Different types of wood have differing degrees of hardness. The hardness of the wood determines how well a floor made from this wood type will resist being assaulted by things falling onto it and also how the floor will respond to the wear and tear of foot traffic, pet toenails, and moving of furniture.
The Janka hardness test was first developed in 1906 by a scientist in Austria named Gabriel Janka. The Janka rating system was then further refined and published for general use in 1927 by the American Society for Testing and Materials (ASTM).
The test is fairly simple, although it is done in a laboratory under standardized conditions and using the average of multiple trials when determining the hardness of a specific species of wood.
To conduct the Janka test, a piece of test wood is placed under a mechanism which shoots a steel ball of .44 inches (11.28 mm) in diameter into the wood surface. The ball is launched with different degrees of force, until it penetrates the wood to a depth of one half the diameter of the ball. The amount of force needed for achieving this is the Janka rating for that wood species.
One confusing point about Janka hardness ratings is that different measurement systems are used in different parts of the world. Janka ratings used by U.S. wood product manufactures are recorded in pounds of pressure. In other countries, Janka ratings are recorded in kilograms or newton force. When considering the hardness of a particular flooring material, it is important to make sure you know which system of measurement is being used, especially if the flooring is imported from abroad.
The Janka ratings of wood do not have anything directly to do with the price of the flooring material. Price is generally determined by available of the product, the cost of transportation, difficulty of milling, and other considerations. But Janka ratings do come into play when you are thinking about how the floor will be used and the geographic location of the installation.
Harder wood is more difficult to saw and wears down saw blades more quickly. Harder woods are also more difficult to nail in place, and pre-drilling of nail holes may be necessary for preventing the wood from spitting when it is nailed. The hardness of a wood species used for flooring also effects how much the wood will flex under pressure, how much it will expand and contract as temperature changes, and whether it will swell when humidity is high.
Janka ratings are only one part of choosing a wood species for flooring. Other considerations are grain patterns, color, sustainability of harvesting practices, price, and availability. However, the Janka rating is an important consideration.
Some points for consideration when choosing the hardness of a wood species for a new floor are:
- How much foot traffic will there be in the room?
- Will there be carpeting over areas receiving heavy foot traffic, or will the floor remain bare?
- Are there pets in the house, and if so, are they large pets with toenails which can scratch the floor?
- How often will furnishings be moved or rearranged?
- How much do temperatures fluctuate in the house?
- How much humidity is present?
- What type of finish will be applied to the floor?
Janka Ratings of Different Wood Species
Even soft woods like yellow pine and Douglas Fir can make beautiful and durable floors, so a low Janka rating does not in any way translate into an inferior wood species for flooring. The choice depends on where the floor will be installed, how it will be used, and how it will be maintained.
Here are the Janka ratings for a selection of popular wood flooring types:
- Douglas Fir, 660
- Yellow Pine, 680-870
- American Cherry, 950
- Walnut, 1010
- Birch, 1260
- Red Oak, 1290
- Beech, 1300
- Ash, 1320
- White Oak, 1360
- Maple, 1450
- Hickory, 1820
- Santos Mahogany, 2200
- Brazilian Cherry, 2820
- Brazilian Teak, 3540
- Brazilian Walnut, 3680
For more help in choosing the best flooring product in the Tri-Cities area, contact Accent on Floors in Hopewell, Virginia.