Hardwood Floors August/September 2019

AT THE SITE

Moisture Testing Accuracy (The 2 Percent/ 4 Percent Rule)

The importance of measuring themoisture content inwood flooring is critical due to the influencemoisture has on somany of the physical properties of wood.Moisture content readingsmay be determined using various moisturemeters developed specifically for this purpose. Handheld thermo-hygrometers and electronicmoisturemeters should be themost important and valued tools in every professional wood flooring installer’s toolbox. The determination of moisture content is an essential part of quality control within the flooring installation process. At the time of installation, as the installer, you should know the moisture content of the wood flooring, the moisture condition of the substrate, and the ambient conditions in the space. All three of these items will dictate whether the facility and the flooring are properly aligned before being installed. Some of the most common technical questions we receive about moisture testing are related to the accuracy of moisture meters.The general questioning is not about the accuracy of a moisture meter as a tool itself, but about the accuracy of its ability to read the different products being tested before being installed when relying on the 2 percent/4 percent rule.This is a multilevel question, and the following will address many of the factors that may affect the reading the meter is giving – or not giving – you. Let’s start with the use of the tool itself. First, consider that moisture meters do not directly measure the amount of moisture in the wood. A value related to the moisture content in the wood is determined from taking measurements of some of the physical properties of the wood that are directly affected by the moisture, or lack of moisture, within.

Whether you are using a pinless (dielectric) meter or a pin-type (electrical resistance) meter, both will give generally reliable readings from as low as 5 percent MC, up to the fiber saturation point (FSP) of the species being tested. There are, however, many user-related variables that can affect the outcome of the readings you are attempting to acquire. Moisture Meter Reading Variables 1. The skill of the operator – although moisture meters normally are very simple to operate, many user errors can affect the accuracy and reliability of the readings. a. Read the user manual. Follow all of the meter manufacturer instructionson theproperuseof the tool.

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