Hardwood Floors August/September 2019

AT THE SITE

Accuracy Based on Averages If every plank in a pallet of flooring were at the same moisture content andmoisture meters gave the same readings on every plank of wood of the same species at the same moisture content, the moisture content of the entire pallet could be determined by one single reading.The actual moisture content of the planks within any pallet of flooring will vary fromplank to plank, and even within each board. Moisture meters can also give various readings on different boards as well as different parts of the same board even at the same actual moisture content. Using the average from a large population of readings, you can determine with confidence that your test results will give you a good snapshot of what is accurate.The higher the number of moisture tests you can take, the more probable it is that the average value will give you an accurate perspective of the floor as a whole. What does an “average” moisture reading mean? First, take a look at what is necessary to determine the MC of an individual board. Using your moisture meter, if you were to take 10 readings from that board, you would likely get a range of high readings, low readings, and readings somewhere in the middle (depending on the characteristics of the board). Then take the sum of those readings and divide that by the number of tests to get the average MC of that board. You can run an oven-dry test on that board to validate the accuracy of your meter. This is not too difficult to do and will get you quantifiable information for that board. Now take a look at the entire floor as one unit (which is more meaningful for installation purposes). If you were to take a moisture reading using the same process as detailed above but of every individual board that you are going to install in the floor, and then take the sum of those readings and divide that by the total number of boards tested, you would get the average MC of the entire floor. In this scenario, you’d also want to remove any extreme, outlying test results (and boards). That average would give you an accurate perspective of what the overall MC is of that floor, but measuring every board is a tedious task. NWFAGuidelines suggest taking a minimumof 40 readings per 1,000 square feet of the flooring being installed, and then averaging the results to get a good representation of the actual

MC of the entire lot of wood. More readings are better than less. Record, date, photograph, and document all of your results. Moisture Testing the Right Species Do you know which species you’re testing? Do you know the proper correction? Moisture meter manufacturers use calibration curves (which are found as an average of 100measurements for the same wood species) to determine corrections for testing that species. Most meter manufacturers have calibration curves for most of the species and subspecies used in the flooring industry and are normally pretty accurate to within +/-1 to 2 percent. If you are installing an oak floor be aware that there are more than 600 different species of oak. More than 30 oak species are commonly used for wood flooring, each with unique characteristics that can affect the outcome of the moisture readings you are taking. Ask the supplier for adequate detail about the species of wood sold to you. A couple of very simple questions can help you identify the species or subspecies of the flooring you are testing. 1. Who is the manufacturer? 2. Where is the wood grown? (Northern-grown oak is quite different from southern-grown oak.) If your supplier can’t get you this information, the manufacturer details should be included on the packaging, in the packaging, or on the underside of the flooring itself. Contact the flooring manufacturer to ask about the species. They may also be able to give you proper moisture testing procedures and species corrections for their product. If not, contact the meter manufacturer for accurate species correction settings. Moisture Testing EngineeredWood Flooring Your moisture meter will give you a reading when you test engineered wood flooring. But do you know if your reading is accurate? If you are not accounting for all of the variables

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