M Plus Timber Glossary
The Janka test measures the force required to embed a 11.28 millimeter (0.444 inch) steel ball into wood to half its diameter. This method was chosen so that the result would leave an indention 100 square millimeters in size. It is one of the best measures of the ability of a wood species to withstand denting and wear. The higher the Janka rating, the harder the wood.
A common use of Janka hardness ratings is to determine whether a species is suitable for use as flooring. The Janka Hardness for our woods are:
The weight of water contained in wood expressed as a percentage of the weight of the oven dry wood.
The relative weight of a substance compared with that of an equal volume of water. The specific gravity of wood is based on the green volume and oven dry weight.
A Specific Gravity of 1 means the wood is the same weight as an equal volume of water.
Tongue and Groove
Tongue and groove or T&G is a method of fitting similar objects together, edge to edge. Tongue and groove joints allow two flat pieces to be joined strongly together to make a single flat surface.