From table legs to support columns, the compressive strength of a given wood species is key in determining the minimum dimensions for your lumber. If you opt for a board that’s too narrow, you risk the possibility of your lumber buckling when incurring a load. And on the flip side, a board that’s unnecessarily girthy can add unnecessary weight & cost to your project.
What Makes a Wood Species Have a High Compressive Strength?
As you may have guessed, the wood species with the highest compressive strengths share a few other traits as well. First & foremost, they tend to be really dense. The measure of this is known as specific gravity, which is measured by the weight of a wood species for a given volume divided the weight of water for that same volume. In the case of North American Softwoods, the top five species in terms of compressive strength all have a specific gravity greater than or equal to 0.45. On the other hand, the other species all register a specific gravity that’s equal to or less than 0.40. Thus, the density of your lumber tends to be good indicator for the strength of that particular wood species.
The other characteristics that influence compressive strength, albeit with weaker correlations, are the hardness rating (lbs) & the stiffness measurement (Mpsi). Generally speaking, harder wood species also have stronger compressive strengths. And likewise, stiffer wood species have stronger compressive strengths as well. There are some exceptions to these two characteristics, but they’re good secondary indicators that you can leverage.