Consistent moisture measurement

Q: I just started two months ago in the pre-finished hardwood flooring industry. I just saw your column and am interested in some advice. Specifically, I am finding it difficult to measure the moisture content of wood consistently. We have three moisture meters and they do not agree - an in-line meter, a pinless meter and a pin-type meter. Our lumber includes red oak, white oak, hard maple and hickory. Using said moisture meters, we get readings from 4 to 17 percent, but none of them agree with each other. What is the best equipment/consultant on the market for our needs?

A: The best moisture meter is one that will be used often.

I did extensive testing on the pinless and pin meters and found that they were within 1 percent MC of the true, oven-dry MC in the 6 to 8 percent MC range.

If you are getting such wide variations, then you need to check whether the appropriate species corrections are being used (especially for the pin-less and in-line meters) and whether temperature corrections are being made (especially for the pin meter).

If there are moisture gradients in the lumber, with the core being wetter, then the pin meter will often read higher than the average MC, as you will be measuring the MC at the tips of the pins which are at the wettest spot. Your in-line meter will likely be sensitive to the width and thickness of the lumber, spacing between pieces and so on. In short, although there will be variations between meters (causing buyer and seller to have a disagreement, so always use the same meter that your customer has), these variations, if the meters are properly used, will be small. I suspect that much of your trouble is due to incorrect meter usage. Check the meter instruction book or check the "Moisture and Wood" training video that the Wood Component Manufacturers Association has for sale.


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Gene Wengert

Gene Wengert, “The Wood Doctor” has been training people in efficient use of wood for 45 years. He is extension specialist emeritus at the University of Wisconsin-Madison.