If you are looking to install new hardwood floors, you have probably come across technical specifications related to hardness, density, and other characteristics of wood. These mechanical properties may make a lot of sense to connoisseurs of the hardwood industry, but to the average homeowner they can also be written in Latin. However, knowing what these measurements mean can help you better understand the type of hardwood flooring you are interested in and whether it is suitable for the room you want to install it in. Here are some key mechanical properties of hardwood, what they measure and why they are important, all in plain language.

Hardness: Often called Janka hardness, this specification measures how resistant a species of wood is to crevices. The test consists of measuring the pounds of force required to embed a small ball (11.28 mm or 444 inches) into the wood at a distance of half its diameter (5.64 mm or 222 inches). Janka hardness is measured in pounds, and the higher the number, the harder the wood. For example, the exotic Ipe has a Janka hardness of 3,680 pounds, while the domestic Douglas fir has a hardness of only 950 pounds. Toughness is important if you are installing the wood in a high traffic area or if the wood will support heavy furniture, such as entertainment centers or pianos.

Modulus of Rupture (MOR): Also called simply Strength, MOR refers to the measure of force required to break the wood. In other words, it is the bearing capacity of the wood. MOR is measured in pounds per square inch or psi. The higher the psi, the stronger the soil. Like hardness, it is important to know MOR if you plan to put heavy furniture on your new floors.

Expansion Module (MOE): Also called Rigidity, MOE is a measure of the stiffness or flexural strength of wood. MOE is also measured in pounds per square inch and, due to the intense force required, is expressed in exponential terms. For example, the MOE of Douglas fir is 1,950,000 psi, expressed as 1,950 1000 psi. The MOE is an important indicator of whether your floors will sag. The higher the MOE, the less likely the wood is to stretch and bend.

Density: The density of a hardwood is related to its weight and hardness, and should be considered in a similar way. Measured in KG per cubic meter (KG / m3), density tells you how much wood is packed into one cubic meter. The higher the density, the heavier and harder the wood will be. Higher density is not always better, especially if you are installing second or third story flooring. Density is also a good indicator of wood’s natural resistance to water and termites. The denser the wood, the harder it is for water and boring insects to get in.

Tangential shrinkage: This property refers to how much a wood species tends to shrink during the drying process. It is expressed as a percentage and is applied only to the width of the plank or board. Shrinkage factor is a good indicator of how much your hardwood floors can warp or sag – the lower the percentage, the more stable the floors will be.

Radial contraction: Similar to tangential shrinkage, radial shrinkage tells you how much wood species can shrink through the thickness of the board. It is also expressed as a percentage. A low percentage is good, but the most important thing is the combination of these two measures. The closer the two are, the more stable the wood will be. For example, Maple has a tangential shrinkage of 9.9% and a radial shrinkage of 4.8%. The differential is 5.1. Walnut, for its part, has a tangential contraction of 7.8% and a radial contraction of 5.5%. Although Walnut’s radial shrinkage is greater than Maple’s, Walnut’s spread is 2.3, much lower, and therefore less likely to warp or sag.

Many of these mechanical properties of hardwood can be confusing and some industry experts even struggle with the concepts. However, knowing the basics of what they measure and why they matter will help you choose the perfect hardwood species for your flooring or decking needs.