Specifications

Color Changes In Wood Flooring

Janka and Understanding the Hardness of Your Flooring

Understanding dents, High heel shoes and your Hardwood Flooring

Understanding Relative Humidity and Temperature effects on your flooring

Shrinkage: Radial, Tangential, and Volumetric

Specific gravity

Mechanical Properties of Wood

1. Bending Strength

2. Max Crushing Strength

3. Work to Maximum Load

4. Weight

5. Stiffness

6. Working ease

Color Changes In Wood Flooring

Whether finished or unfinished, wood changes color over time due to oxidation and exposure to light. Some species darken in color over time, while others lighten. There is no set value for "color fastness" of a species, so contractors and their customers need to be aware of how much change they should expect from the species they choose. Certain species, including American cherry, Brazilian cherry and many imported species, are especially notorious for their tendency to change color. A demonstration of this change is shown below. Some color change is to be expected for all species and a drastic change can be expected for others. The change over time is gradual but rugs should be moved on a regular basis to avoid color change patterns appearing on the floor.

Janka and Understanding the Hardness of Your Flooring

When choosing hardwood flooring a combination of factors need to be considered prior to purchase. One property is the Janka rating of your flooring. Janka 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 diameter was chosen to produce a circle with an area of 100 square millimeters). The higher the Janka number, the greater the wood's ability to resist dents and other wear. While it's true that the hardwood used in flooring is durable enough to withstand normal use, that doesn't mean that the wood won't dent or mar with a hard enough impact. Appliances, furniture, a high-heeled shoe, dog paw, or pebble stuck in a sole could easily damage and will eventually leave dents in a hardwood floor even with the hardest species. Wood is a natural material and every piece is different. In the case of solid and engineered flooring it will have the same Janka rating even if the construction is different. It also indicated how hard the wood will be to saw and nail. Some wood that would be great in terms of wear would be very difficult to install. However with all the science considered there is still a "optical illusion factor" to dents. The different grains of wood will show the dents to different degrees. The 'closed grain' hardwoods (usually Maple, Birch,) have such a subtle grain, that they will show dents more than the open grained hardwoods. The 'open grain' hardwoods - Such Oak and Ash, might be a little softer than say Maple, but since they have such wild grains, the dents will show less. In addition, large windows with strong light will accentuate dents in hardwood.

High Ranking (1800 - 4000)

Harder wood types can be found in the upper portion of the Janka Scale and are generally recommended for high-traffic areas in homes and businesses.Woods that have a high ranking include Brazilian Cherry, Cumaru and Ipe.

Medium Ranking (1200 - 1800)

Medium density woods are good for most home applications, such as living rooms and dining rooms. Certain woods may not be recommended for kitchen use. Some common types are White Oak, Red Oak, and Maple.

Low Ranking (540 - 1200)

Wood and bamboo types on the lower end of the Janka Scale are best for low-traffic areas such as bedrooms and closets. Softer wood types include Black Cherry and Black Walnut.

Understanding dents, High heel shoes and your Hardwood Flooring

To all those high heel admirers, do you know exactly how much pressure is generated under you heel? You would be surprised! Indeed we adore our shoes and they look great, but with the immense pressure under a high heel, you may as well use it as a weapon. Pressure is defined as force over area. Pressure is directly proportional to the force and inversely proportional to area. This inverse relationship of Pressure is an important concept when it concerns the immensity of pressure. The significance of the high heel comes into play because it has such a minute area. Due to this fact, the pressure under that high heel is extremely large. Did you know that a 100-pound woman walking in high heels has an impact of 2,000 pounds per square inch. An exposed heel nail (from over-worn heels) can exert up to 8,000 pounds per square inch. When you look at the Janka rating of each wood species you can see how dangerous a high heel shoe can be to flooring. Wood is a natural material and every piece is different. The above numbers are averages of samples testing and should be used as a guideline only. Denting is dependant on several factors and we can not guarantee that your floor will not dent if you choose to wear high heel shoes or an item impacts the flooring.

Understanding Relative Humidity and Temperature effects on your flooring

The movement of water into and out of the boards doesn't stop when they leave the mill.

There is almost always some moisture in the air (we call it humidity). If there is more moisture in the air than in the wood, the moisture tries to diffuse uniformly, moving moisture into the wood. If there is more moisture in the wood than in the air the process is reversed and some water moves back into the air. If conditions never changed, the movement of moisture into and out of the wood would eventually stop. At this point the wood would have reached the equilibrium moisture content. Of course conditions do change. We're primarily interested in two of the changes - relative humidity and temperature. If you live in an area that has cold, dry winters and warm or hot humid summers you will see a greater change in the moisture content of wood than in an area where there is little difference between winter and summer. If you live in a coastal area the relative humidity is likely to be higher than in an inland area. In areas with cold winters, forced-air heating systems will further lower indoor humidity. In these examples your flooring may experience seasonal gaps or cupping which are all cause by variation in the temperature and relative humidity in a house. In extreme cases you may even experience cracking if the surroundings are kept too dry, that is below 40% relative humidity.

How much change occurs depends on how much the moisture content changes and on the species of wood. Different species react differently to moisture changes. This will be explained in the T/R ratio section further ahead. Flooring manufactures target a moisture content of 6-8% to ensure that the regional effects of moisture are minimal on the installed flooring. Moisture content is expressed as a percentage (a ratio). The wet wood is first weighed, then dried and weighed again. The difference in the two weights is then divided by the dry weight to get the percentage moisture content As moisture content changes, wood changes least in the longitudinal direction. In fact, it changes so little longitudinally that we usually don't even account for the change. As moisture content changes, wood changes most in the tangential direction. As moisture content changes, wood changes less in the radial dimension than it does in the tangential direction.

Shrinkage: Radial, Tangential, and Volumetric

These values measure the change in wood when going from a freshly cut (green) state, to an oven-dry (0% moisture content) state. Radial shrinkage is the amount the wood has shrunk across the grain. Tangential shrinkage is a measurement of the amount the wood has shrunk along the grain. (Not to be confused with longitudinal shrinkage, which measures the shrinkage along the entire length of the board, which is usually very slight,: under .5%) Volumetric shrinkage is an overall measurement of how much the wood has shrunk in volume during the drying process.

T/R Ratio is the ratio of tangential to radial shrinkage. The smaller the ratio, the more likely a wood is to stay flat and avoid warping due to seasonal expansion and contraction. Tangential % is shrinkage across the board this in combination with the T/R ratio is a good indicator of stability. However, the largest factor for stability is the consistency in the moisture content of the flooring achieved by proper equalization in kilns and proper tolerances.

The shrinkage numbers tell the magnitude of the wood's movement with changes in humidity,and the T/R ratio shows the stability of the changes. These numbers are very valuable in determining how stable the wood will be in service with respect to changes in relative humidity. However no matter what the numbers show for stability and water or excessive moisture and wood floors don't go well together.  Wood swells with high moisture levels which will cause wood floors to cup and buckle and the grain to be raised.. Use a moisture meter to test the moisture levels in both the wood flooring and the substrate you are going over. Acclimate the hardwood prior to installation, use proper expansion gaps and follow the APPALACHICAN MAINTANENCE GUIDE installation procedures. If moisture levels are too high do not install hardwood flooring.

Specific gravity

When using a pinless moisture meter typically the specific gravity is needed for the setup. The below table gives a guideline for the Specific gravity. However be aware there are several inaccurate meters on the market and be careful. The most accurate method in determining moisture is by following ASTM procedure to obtain the moisture content by use of a laboratory oven.

Mechnacial Properties of Wood

Bending Strength:  

 Also known as modulus of rupture (MOR), this is a measure of a specimen's strength before rupture. It can be used to determine a wood species' overall strength; unlike the modulus of  elasticity which measures the wood's deflection, but not its ultimate strength. (That is to say, some species of wood will bow under stress, but not easily break.) MOR is expressed in pounds-force per square inch (lb f/in2 ) or kilopaschals (kPa). This number is given for wood that has been dried to a 12% moisture content, unless otherwise noted. : Maximum bending stress before failure occurs. Rankings based on modulus of rupture in psi: < 11000 = low (weak); 11000 to 14000 = medium (moderately strong); > 14000 = high (strong).

 Max Crushing Strength:

 : Average ovendry weight. Rankings based on pounds per cubic foot: < 33 = low (light); 33 to 43 = medium (moderately heavy); > 43 = high (heavy).

Stiffness

 : Elasticity or ability to resist bending stress. per 1000 psi

Stiffness	Green	Dry
Ipe	2901	3129
Yellow Birch	1500	2010
Santos Maghogany	2040	2431
Walnut	1480	1790
Hickory	1370	1730
Jatoba	1843	2422
Tigerwood		2479
Cherry	1380	1655
Maple	1550	1830
Red Oak	1440	1775

Working ease

 How easily the wood is worked. These rankings are somewhat more subjective than those for the other criteria but they take into account things such as
blunting effects on cutting edges and how easily the wood splinters, chips, and burns. Rankings: low (works with difficulty); medium (works fairly easily); high (works easily).