When it comes to the relative harness of Pine flooring, many people have an incorrect perception of the relative hardness of Heart Pine.   When they think of Pine, many automatically think “soft”.   While it is true that some Pine species, like Northern White Pine, are soft, Southern Heart Pine compares very favorably with other traditional hardwoods used for wood flooring, especially the old standard, Northern Red Oak.

As a matter of fact, using the industry standard “Janka Hardness” test, Heart Pine is rated only 5% less than Northern Red Oak.This can be illustrated by using the chart under the “RELATIVE HARDNESS OF SELECTED WOOD FLOORING SPECIES” section below.

When it comes to stability, it is typically discussed as the dimensional change coefficient for the various species, measured as tangential shrinkage or swelling within normal moisture content limits of 6-14 percent.  

In the case of a solid heart pine floors the has a change coefficient of .00263 and .00265.   This is 29% MORE stable than solid Northern Red Oak.   This can be illustrated by using the chart under the “RELATIVE STABILITY OF SELECTED WOOD FLOORING SPECIES” section below. 

However, when comparing and engineered wood flooring product, there as an additional issue to understand.   An engineered product, because of its cross-banded, multi-ply construction is even more stable than it’s solid counterpart.   As an example, in moisture conditions of 18% a 5” wide, ¾” solid plank of wood flooring can expand in width as much as 1/8” or more and in length 8/32”.   In contrast the same 5” wide engineered flooring experiences virtually no expansion in width or length.   This is extremely important when considering the location and application of a particular type of wood floor.  

HARDNESS & STABILITY CHARTS
We invite you to use the charts on the following pages as a reference.   We also encourage you to contact us with any specific questions concerning a particular application.

RELATIVE HARDNESS OF SELECTED WOOD FLOORING SPECIES
(Ranked by Janka hardness rating)
The Janka (or side) hardness test is a measure of the hardness of wood, produced by a variation on the Brinell hardness test. 

The test measures the force required to push a steel ball with a diameter of 11.28 millimeters (0.444 inches) into the wood to a depth of half the ball's diameter.   The results are stated in various ways in different countries, which can lead to confusion, especially since the name of the actual units employed is often not attached.   In the United States, the measurement is in pounds-force.

The hardness of wood usually varies with the direction of the grain.   Typically testing is done on the surface of a plank and is said to be for "side hardness", as is the case with the Janka test.  It is one of the best measures of the ability of a wood species to withstand denting and wear.   By the same token, it is also a good indicator of how hard or easy a species is to saw or nail.  

As stated previously, when viewing the chart you can see that Heart Pine is rated only 5% less than Northern Red Oak.        

* Source: Hardness ratings for most species taken from Wood Handbook: Wood as an Engineering Material (Agriculture Handbook 72. Forest Products Labratory Forest service U.S. Department of Agriculture: revised 1987), except for Australian cypress. wenge, African padauk, merbau and santos mahogany: which were provided by International Hardwood Flooring: Heart Pine by Mountian Lumber and mesquite by Mesquite Products of Texas.* Douglas fir rating is an average of ratings for Coast, Interior West and Interior North species.

NOTE: Some information sources say or imply, incorrectly, that Janka hardness is measured in units of pressure, such as pounds per square inch, and that side hardness is a synonym for Janka hardness.

RELATIVE STABILITY O F SELECTED WOOD FLOORING SPECIES                 
(Ranked by dimensional change coefficient)*
The numbers in the chart reflect the dimensional change coefficient for the various species, measured as tangential shrink- age or swelling within normal moisture content limits of 6-14 percent.   Tangential change values will normally reflect changes in plainsawn wood. Quartersawn wood will usually be more dimensionally stable than plainsawn.
The dimensional change coefficient can be used to calculate expected shrinkage or swelling.   Simply multiply the change in moisture content by the change coefficient and then multiply by the width of the board.

Source: Stability ratings taken from Wood Handbook: Wood as an Engineered Material (Agriculture Handbook 72 Forest Products Laboratory.    Forest Service. U.S. Department of Agriculture: revised 1987).
*Solid Flooring

Other Resources
Standards: ASTM D1037-99. Standard Test Methods for Evaluating Properties of Wood-Base Fiber and Particle Panel Materials.
ASTM D143-94(2000)e1 Standard Methods of Testing Small Clear Specimens of Timber.
ISO 3350:1975. Wood–Determination of static hardness.
ISO 3351:1975. Wood–Determination of resistance to impact indentation.