Janka hardness unit By Region

The Janka Scale for our hardwood species

  • Andiroba 1,220 lbf (5,430 N)
  • Taurai 1650 lbf (7339.56 N)
  • Garapa 1700 lbf (20,040 N)
  • TataJuba 1,720 lbf (7,650 N)
  • Cambara 1,730 lbf (7,562 N)
  • Tigerwood 2,160 lbf (17,500 N)
  • Cuban Laurel 2,340 lbf (10,390 N)
  • Jatoba 2,350 lbf (25,100 N)
  • BloodWood 2,900 lbf (12,900 N)
  • Itauba 2,900 lbf (12,900 N)
  • Angelim Pedra 3040 lbf (17,600 N)
  • Angelim Vermelho 3,160 lbf (14,050 N)
  • Massaranduba 3190 lbf (29,290 N)
  • Cumaru 3540 lbf (25,580 N)
  • Ipe 3680 lbf (25,860 N)

How hard is wood ?

How is it determined ?

What does the test consist of ?

These are just a few questions that might come up when you hear about how hard a wood is.

The fact is not many people understand the testing, and even fewer look to improve upon it. The Janka Scale has done a good job in giving a broad reference to relative hardness. The thing it has solved is some of the issue’s that have evolved from it.

Here’s how the Janka test works:

  1. A small steel ball 11.28mm (.444 in) is placed on a board.
  2. Pressure is then applied to the ball until it sinks half of its width into the piece of wood.
  3. When the ball reaches the halfway point the test is completed and the results recorded.
  4. For consistency reasons the test is conducted on a flat grain instead of the sides or ends.

Problems With the Janka Test ?

As good as the Janka test is for a “general idea” it does have some issues. Anyone who spends a lot of time around hardwood knows how much grain can vary. The variance in that grain changes the hardness. A small steel ball only tells one small story, about one small part, of one small piece of wood. Within a single piece of decking it is conceivable that there could be several different strengths. Another problem is wood have a hard section (autumnal growth) of grain and a softer (spring growth) section in which the piece isn’t being tested as a whole unit.