Wood Species Data

Elemental Wood Species Data

Reliable measurements for the mechanical properties of hundreds of wood species can be very difficult to find. Further, there is an inherent variability in these mechanical properties for a given species. For more esoteric wood species, there is often no reliable data on the mechanical properties of the wood. As a way out of this problem, people realized that the “basic” density of the wood is strongly correlated with virtually all mechanical properties of the wood. So, in 2007, Araujo performed a regression analysis on wood properties from 163 Brazilian species. He assumed that all properties were only a function of the basic density.

While the resulting regression curves did not precisely fit the actual data, the curves provide a not unreasonable way to estimate many of the mechanical properties of an unknown sample of wood using only the wood’s basic density. The data in our table of mechanical properties is that predicted by Araujo’s regression curves, not actual measured data. If reliable data is available for any of these species, those values should be preferred over those in the table.

Source: H.J.B. de Araujo, Relações funcionais entre propriedades físicas e mecânicas de madeiras tropicais brasileiras. Curitiba, Parana, Brasil.

Janka Hardness

The industry standard method for determining the hardness of wood products is called the Janka hardness test. Janka hardness of a given wood species is defined by a resistance to indentation test as measured by the load (pounds of pressure) required to embed a 11.28mm or 0.444″ diameter ball to one-half its diameter into the wood. The Janka values presented are the average of penetrations on both flat grain or plain sawn and vertical grain or quartersawn boards.

Stiffness

Modulus of Elasticity (MOE) Rating

Modulus of elasticity ratings are derived from the stiffness or resistance to bending of the particular wood species. These ratings pertain to longitudinal modulus of elasticity, not tangential or radial ratings.

Strength

Modulus of Rupture (MOR) Ratings

The modulus of rupture is a measure of the maximum load carrying capacity of a given species in bending strength and is proportional to the breaking point or maximum strength as borne by the specimen.It is measured in pounds per square inch (PSI).

Density

A wood product’s weight is determined by combining the density of the basic wood structure with the material’s moisture content. The density of wood, exclusive of water, varies a great deal within and between species. Density variations within a particular species of approximately 10% should be considered normal. A wood’s weight is always partially contingent on its moisture content, so moisture should always be taken into consideration. The figures below represent the density at approximately 12% moisture content.