WOOD HARDNESS AND THE JANKA SCALE
Wood species hardness determination follows a very precise method which allows to rank both hardwoods and softwoods on a comparable scale, from harder to softer. The method was created in 1906 by Gabriel Janka, an Austrian-born wood researcher, and in 1972 standardized by the American Society for Testing and Materials (ASTM).
Now known as the Janka Scale, it quantifies the resistance of a wood species (in pound-force lbf) to denting by measuring the force required to embed a 0.444” steel ball to half its diameter into a plank.
Hardwood starts at a rating of 950. If all can answer standard residential needs, the best species that offers superior dent resistance while being not so hard that they are difficult to saw and nail (increased installation costs), are: Hard Maple (aka Canadian or Sugar Maple), Red Oak, White Oak, Ash and Beech.
Sub-species differentiation is critical. For example, there are 3 common sub-species of Maple in North America, but each has a very different hardness level and resistance performance: Hard Maple at 1,450 vs Red Maple at 950 vs Silver Maple at 700 (half of Hard Maple).